Browse Topic: Diesel fuels

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Investigation of the Combustion of Stearic Acid-Coated Pure Aluminum Powder as Additives in Biodiesel and Diesel Blends04-19-02-00106/8/2026
In the present study, research was conducted to increase the combustion efficiency in a diesel engine by adding 100 and 200 ppm aluminum powder to diesel and biodiesel (produced from 10% spent coffee ground oil and 90% waste cooking oil) blends. Aluminum powder is a flammable metal. Due to this feature, it has been used as an additive to liquid fuels in many studies in the literature. In general, it has been reported that thermal efficiency increases with the addition of aluminum particles. However, the high explosion sensitivity of aluminum can affect its stable combustion. In addition, Al is a metal that can be easily oxidized. Therefore, coating aluminum is considered a good solution. Stearic acid has been suggested in the literature as a suitable material for coating aluminum. In this study, stearic acid, a saturated fatty acid, was used to coat aluminum particles. Stearic acid is a good surfactant, hydrophobic substance, and plasticizer. It is also a more environmentally friendly substance compared to its counterparts. In this study, aluminum particles were coated with stearic acid to increase the combustion efficiency of Al particles. To make the coating, stearic acid was dissolved in ethanol and mixed with Al particles. Then, the stearic acid coating was achieved by self-assembly using the evaporation technique. As a result of experiments conducted by adding aluminum and stearic acid-coated aluminum to diesel and biodiesel blends, the thermal efficiencies of DAl200, DAl100, and DSA@Al100 fuels were 2.99%, 3.21%, and 4.59% higher than that of standard diesel fuel, respectively. Likewise, the thermal efficiencies of B10D90Al200, B10D90Al100, and B10D90SA@Al100 fuels were 2.73%, 2.99%, and 3.62% higher than that of standard diesel fuel, respectively.
Kül, Volkan Sabri, Akansu, Selahaddin Orhan, Sarıtaş, Mehmet
Effect of Burning Biomass Fuel Cyclohexanol on Diesel Engine Performance2026-99-17085/22/2026
Against the backdrop of growing global demands for energy sustainability and stricter emission regulations for diesel engines, this study investigates the performance implications of incorporating cyclohexanol—a renewable oxygenated fuel—into diesel fuel blends. Using a marine medium-speed diesel engine as the experimental platform, the research systematically evaluates engine performance and emission characteristics across a range of cyclohexanol-diesel blend ratios under low, medium, and high load conditions. Experimental findings reveal multifaceted effects of cyclohexanol blending on engine operation. Combustion of the blended fuels enhances the engine’s dynamic performance, particularly under medium and high loads, where the maximum in-cylinder burst pressure exhibits a noticeable increase. This improvement is attributed to cyclohexanol’s oxygen-carrying capacity, which promotes more vigorous and sustained combustion reactions. In terms of emissions, increasing the proportion of cyclohexanol in the fuel blend leads to significant reductions in soot and carbon monoxide (CO) emissions, reflecting the cleaner-burning properties of the oxygenated component. However, this is accompanied by an uptick in nitrogen oxide (NOx) emissions, likely due to the elevated combustion temperatures generated by the more efficient fuel oxidation process. From an economic perspective, cyclohexanol blending at consistent load levels induces a postponement in the crank angle at which peak heat release occurs during combustion. This temporal shift prolongs the effective combustion duration, enabling more complete fuel utilization within the cylinder. Consequently, fuel consumption rates decrease, and overall engine efficiency improves, highlighting the potential of cyclohexanol blends to enhance operational economy in marine propulsion systems. In summary, this study underscores the complex trade-offs associated with cyclohexanol-diesel blends: while they offer tangible benefits in power output, fuel efficiency, and reduced particulate emissions, managing the increase in NOx emissions remains a critical challenge. The results provide a foundational framework for advancing biofuel applications in marine engines, emphasizing the need for integrated emission control strategies to optimize the balance between performance and environmental sustainability.
Chen, Ke, Yang, Chenxi, Wang, Yibin, Fan, Jinyu, Liu, Yuchen, Ye, Zixiao, Huang, Jialiang
Reactivity Controlled Compression Ignition (RCCI) Combustion Engine Characteristics Fuelled with Diesel/Compressed Natural Gas (CNG) and Diesel/Methanol Fuel Pairs2026-01-03194/7/2026
Ultra-low oxides of nitrogen (NOx) and particulate matter (PM) from reactivity-controlled compression ignition (RCCI) combustion have motivated researchers to explore more about low temperature combustion (LTC) engines. In this study, a comparative analysis of combustion, performance, and emission characteristics of RCCI combustion fuelled with diesel/compressed natural gas (CNG) and methanol/diesel fuel pairs has been carried out with respect to baseline compression ignition (CI) combustion. All experiments were performed in a constant speed engine at four different engine loads. For RCCI combustion experiments, a constant premixed ratio (rp= 0.50) and 15% exhaust gas recirculation (EGR) were used. The results exhibited a significant reduction in NOx emissions and relatively smoother RCCI combustion compared to baseline CI combustion. RCCI mode combustion resulted in relatively superior engine performance compared to baseline CI combustion, especially at higher engine loads. A comparison between the RCCI combustion fuelled with gaseous fuel (CNG) as a low reactivity fuel (LRF) and a liquid fuel (methanol) showed a slightly lower brake thermal efficiency (BTE) of CNG/diesel fuelled RCCI combustion compared to methanol/diesel fuelled RCCI combustion at low loads. As the load increased, the trend of BTE was reversed. The combustion characteristics of CNG/diesel fuelled RCCI combustion were found to be more stable compared to methanol/diesel fuelled RCCI combustion. The NOx emissions were lowest in methanol/diesel fuelled RCCI irrespective of engine load. At low load, methanol/diesel fuelled RCCI suffered from higher hydrocarbon (HC) and carbon monoxide (CO) emissions, while CNG/diesel fuelled RCCI maintained relatively lower HC and CO emissions.
Saikia, Bhargav, Kant, Akshay, Gupta, Abhishek, Singh, Akhilendra Pratap
Technical Outlook on the Potential of HVO and Biodiesel Blends for Cleaner Combustion2026-01-03164/7/2026
The increasing need to decarbonize the transport sector is accelerating the adoption of renewable and low-carbon fuels such as Hydrotreated Vegetable Oil (HVO) and biodiesel as sustainable substitutes for fossil diesel. These fuels are evaluated as drop-in solutions requiring no engine recalibration, enabling immediate GHG emission reduction in existing diesel fleets. This study experimentally investigates the combustion, performance, and emission characteristics of a turbocharged common-rail two-cylinder diesel engine (Kohler LWD 442 CRS) operated with conventional fossil Diesel, pure HVO (Hydrotreated Vegetable Oil), and an HVOB20 blend (80% HVO and 20% biodiesel produced from waste cooking oil and animal fats). Tests were carried out under steady-state conditions at the DIIEM Engine Laboratory of Roma Tre University. The analysis focused on in-cylinder pressure evolution, brake power, brake specific fuel consumption (BSFC), and both regulated and unregulated emissions. Regulated species include carbon monoxide (CO), nitrogen oxides (NOₓ) and particulate number concentration (PNC > 23 nm, PMP-compliant), while unregulated emissions cover non-methane hydrocarbons (NMHC), formaldehyde (HCHO), nitrous oxide (N₂O). CO and NMHC are key indicators of incomplete combustion: CO results from partial oxidation of carbon during fuel burning, and NMHC represents the fraction of unburned hydrocarbons excluding methane. Both pollutants decreased markedly with renewable fuels, indicating a more complete oxidation process promoted by HVO’s paraffinic composition and FAME’s oxygenated nature. Experimental results show that HVO and HVOB20 slightly increase brake torque and reduce BSFC compared with fossil diesel, despite their lower density and heating value. Combustion remained stable across all operating conditions, with negligible variations in ignition delay and pressure rise rate. NOₓ emissions were comparable or marginally higher at medium engine speeds, likely due to faster ignition and elevated combustion temperatures. Unregulated species such as HCHO and N₂O decreased or remained negligible with increasing renewable content, while PNC and count mean diameter (CMD) were significantly reduced, confirming cleaner combustion and reduced soot formation. Overall, both HVO and HVOB20 demonstrated improved combustion efficiency and emission performance while ensuring full engine operability without calibration adjustments. These findings confirm the technical viability of renewable diesel fuels as immediate, drop-in solutions for reducing GHG emissions.
Zaccai, Martina, Chiavola, Ornella, Palmieri, Fulvio, Verdoliva, Francesco
Challenges to Ranking Diesel Fuels for NO x Emissions Using a Constant-Volume Combustion Chamber2026-01-03484/7/2026
The market is witnessing an unprecedented proliferation of low-emission fuel components. To effectively evaluate the suitability of these novel fuels for engine applications, fuel blenders and original equipment manufacturers require rapid and reliable assessment methodologies. Traditionally, such evaluations rely on comprehensive engine testing, which, while thorough, is both time-intensive and costly. In response to the growing diversity of emerging fuel options, this work aims to establish a streamlined screening approach capable of effectively replicating the outcomes of full-scale engine testing. We examined the use of a constant volume combustion chamber for the measurement of fuel effects on NOx emissions, with the goal of developing a method to rapidly screen or rank fuels in a small - volume experiment. A small amount of fuel was injected into air at 650°C and 20 bar, where it ignited and burned. The chamber was sampled post-combustion using a chemiluminescence NOx analyzer. Extensive sampling method development was required to obtain repeatable results. Seven hydrocarbon fuels and two biodiesel fuels were tested, all of which have shown difference in NOx emissions in past engine studies. When using a single injection event to deliver the same amount of fuel energy, the test method could not clearly demonstrate the difference in NOx emissions between the hydrocarbon fuels as reported in engine combustion studies. Heat release rate analysis suggested this was caused by large differences in ignition delay and premixed burn fraction for the fuels tested. To improve this, a dual-injection strategy was used. It included a small “pilot” injection followed by a main injection, timed based on each fuel’s ignition delay to coincide with the pilot heat release. This strategy helped reduce differences in heat release caused by how quickly each fuel ignites. For hydrocarbon fuels, this approach revealed the expected relationship between NOx emissions and fuel type. Two soy biodiesel samples did not show higher NOx as observed in engine studies. This suggests that the current test method may not fully reflect engine conditions where biodiesel tends to produce more NOx. Further improvements in test method and setup are recommended to better align constant volume chamber conditions with engine conditions under which biodiesel shows increased NOx emissions.
Luecke, Jon, Rahimi, Mohammad, Mohamed, Samah, Naser, Nimal, Chausalkar, Abhijeet, McCormick, Robert
Impact of Hydrogen on Methane and Pollutant Emissions over Three-Way Catalysts with Natural Gas–Hydrogen Blends2026-01-03574/7/2026
Blending natural gas (NG) with hydrogen (H₂) can improve combustion and engine performance while potentially facilitating the catalytic conversion of methane and other pollutants, resulting in cleaner tailpipe emissions. This study evaluates the impact of H2 on the conversion of methane, CO, and NOx emissions on a commercial three-way catalyst (TWC) in a flow reactor using synthetic gas mixtures that simulate stoichiometric engine exhausts with NG or NG+H₂ combustion. The work examines whether, and how, the additional amount of H₂ in the exhaust stream affects the conversion efficiency of methane and other pollutants. Experiments were conducted with both degreened and aged catalysts under controlled conditions, systematically varying temperature, the air-to-fuel equivalence ratio (λ), and λ modulation. Test conditions covered λ values from 0.996 to 1.000 to represent nominally stoichiometric engine operation with different λ modulation amplitudes, as well as a range of temperatures to inform control strategies for effective CH₄, CO, and NOₓ reduction. Overall, the results show that hydrogen addition significantly improves the conversion efficiency of CH₄ and NOₓ, particularly at temperatures below 500 °C. More significantly, this study highlights that exhaust gas composition, operating temperature, λ management, and the oxygen storage capacity of the TWC all play major roles in affecting the tailpipe emissions from NG and NG+H₂ combustion.
Prikhodko, Vitaly, Wang, Min, Park, Yeonshil, Chen, Hai-Ying, Pihl, Josh
The Effect of Diesel Fuel Compositions and Distillation Properties on PM Production2026-01-03464/7/2026
Although overall demand for petroleum products is expected to decline, diesel fuel demand is projected to remain stable. Modern refineries produce diesel fuel by blending straight-run diesel fuel with cracked fractions like Light Cycle Oil (LCO) and kerosene. Cracked fractions are characterized by high concentrations of aromatic and naphthenic compounds compared to straight-run diesel fuel, whereas kerosene exhibits lighter distillation properties. This study quantitatively assesses the effects of diesel fuel composition and distillation properties on PM formation using engine bench tests designed to reflect practical refinery blending operations. To isolate the impact of fuel composition, test fuels were formulated with substantial variations in aromatic and naphthenic content, while other key parameters were held constant. To investigate the influence of distillation properties, two sets of test fuels were prepared: one series with varying front-end volatility achieved by adjusting kerosene content, and the other series with modified back-end volatility via cutting back-end fraction. A regression-based estimation equation for PM production was developed from experimental results, enabling quantification of the individual contributions of compositional and distillation parameters. The findings indicate that aromatic compounds have a greater influence on Particulate Matter (PM) formation than naphthenic compounds, with naphthenobenzene having a more pronounced effect than alkylbenzene. Furthermore, both aromatics and naphthene with polycyclic structures were found to contribute more substantially to PM emissions than their monocyclic counterparts. The study also confirms that enhancing the light-end volatility of diesel fuel - either through kerosene blending or cutting back-end fraction - effectively reduces PM production.
Katori, Kohei, Seo, Masahiro, Takahashi, Ko
CFD Simulation of Combustion and Emission Characteristics of Pure Spirulina Microalgae Biodiesel in a Single-Cylinder DI Diesel Engine2026-28-00432/12/2026
In this study, the combustion and emission characteristics of a single-cylinder direct injection (DI) diesel engine fueled with Spirulina biodiesel along with diesel blends were examined using a combined CFD and thermodynamic simulation framework. Three test fuels, including pure diesel (D100), Spirulina biodiesel blends (B20 and B40), and pure Spirulina biodiesel (B100), were analysed at 1500 rpm under full load. In the first stage, CFD simulations were performed in ANSYS Fluent, where the Discrete Phase Model (DPM) was applied to capture spray atomization and droplet evaporation, while a non-premixed combustion model coupled with the RNG k-ε turbulence model was employed to resolve in-cylinder flow and heat release dynamics. Subsequently, the Diesel-RK software was utilised to predict engine performance and exhaust emissions based on compression ratios (18.5) and injection timings. Results from the CFD analysis revealed faster atomization and reduced ignition delay for biodiesel blends compared with pure diesel, supported by enhanced cylinder pressure development. Diesel-RK simulations indicated that Spirulina biodiesel blends (B20) generally improved brake thermal efficiency at higher compression ratios while increasing brake specific fuel consumption due to their lower calorific value. Emission analysis showed consistent reductions in CO, HC, and smoke capacity with higher biodiesel content, while NOx emissions exhibited a rising trend. The findings confirm Spirulina biodiesel (B20) as a viable renewable fuel and highlight simulation-driven strategies for optimising compression ratio and injection timing in CI engines..
Kumar, B Varun
Enhancing Combustion, Performance and Emission Profiles Using Kapok Methyl Ester Blends with Hydrogen2026-28-00582/12/2026
This study investigates the potential of using a dual green alternative fuel combination, the one is hydrogen fuel and another one is biodiesel for enhancing the Performance, combustion and emission profile of a compression ignition engine. The kapok oil biodiesel was blended with Diesel in proportions of 20% (K20) and 40% (K40) by volume. The hydrogen gas was supplied at a constant flow of 4 liter per minute (LPM). The experimental fuels are neat diesel D100, K20 (80% Diesel and 20 % kapok methyl ester), K40 (60% Diesel + 40 % Kapok methyl ester), K20 + H4L (K20 with 4 LPM hydrogen) and K40+H4L (K40 with 4 LPM hydrogen). These test blends are investigated in a single cylinder direct injection CI engine under 0% to 100% load conditions at a fixed speed of 1500 rpm combustion, and emissions characteristic were evaluated and compared with base fuel. The outcomes indicated that the use of B20 and B40 blends without hydrogen led to reduced BTE because of their lower cetane number and calorific value. Additionally, higher viscosity of the blends resulted in increased BFSC. However, the introduction of hydrogen and the K20H fuel blend demonstrated notable emission improvements compared to conventional diesel, achieving reductions of 9–11% in unburned hydrocarbons, 5.3% in carbon monoxide, and approximately 8% in nitrogen oxides (NOₓ). These findings highlight the potential of K20H as a cleaner alternative fuel.
Anbarasan, B, M, Kumaresan, Balamurugan, S, Rajesh, Munnusamy
3D CFD Combustion Evaluation of Hydrotreated Vegetable Oil (HVO) as a Potential Alternate Fuel for the Future CI Engines2026-26-01131/16/2026
Transportation industry is facing a growing challenge to reduce its carbon footprint and utilize the carbon neutral, more environmentally sustainable fuels to comply with the goal of carbon neutrality. Implementation of carbon free fuels such as Hydrogen, Ammonia and low carbon fuels such as Methanol, Ethanol can significantly reduce the greenhouse gas emissions, but these fuels are suitable for SI engine architecture due to their high-octane ratings. Hydrotreated Vegetable Oil (HVO) is one of the few fuel solutions available today with a high Cetane rating (70-80), that can be used as a drop-in fuel in the existing CI engines, with minimal modifications. The main constituent of HVO is pure alkane and it can be produced from feedstocks such as vegetable oils, animal fats, various wastes and by-products. A closed cycle 3-D CFD combustion simulation using a detailed chemistry-based solver has been conducted with the HVO, on a three cylinder, naturally aspirated water-cooled CI engine at its full load, rated rpm. Chemical kinetics file with 92 species and 1240 reactions has been used as a surrogate for the HVO to conduct the combustion simulation. The peak firing pressure has been observed to be lower by 3% and SoC is advanced by 2o CA for HVO as compared to the baseline diesel. HVO combustion manifests the same thermal efficiency with respect to its diesel counterpart. Soot emission has been 36% lower for HVO due to the absence of unsaturated hydrocarbons and the NOx emission is lowered by 32% for HVO, as a consequence of a lowered in-cylinder temperature. Simultaneously, a 13% reduction in CO, 77% reduction in UHC and 74% reduction in VOC have been observed for HVO as compared to diesel. A meticulous monitoring of unregulated emissions proves that the HVO exhaust is devoid of their presence. The 3D CFD combustion exploration unveils that the HVO indeed holds the potential to be a promising drop-in alternate fuel for the next generation CI engines.
Tripathi, Ayush, Mukherjee, Nalini, Nene, Devendra
Combustion Dynamics and Performance Optimisation Using Higher HCNG Blends for Decarbonising the Gas Genset Sector2026-26-02511/16/2026
Air pollution is profligate becoming a serious worldwide problem with the increasing population and its subsequent demands. Diesel, Gasoline, Natural Gas, Propane, etc., are some of the traditional fuels used in the power generation sectors. Diesel fuel, popularly utilized for backup power in critical operations, is valued for its swift activation time. This makes diesel generators a preferred choice for commercial properties and hospitals requiring reliable emergency power. Moreover, natural gas, distributed through local utility grids, provides a convenient and readily available fuel source for generators, eliminating the need for on-site fuel storage. On the other hand, CPCB has instructed to modify the emission regulations for genset engines for decarbonization and development clean fuel. The change from CPCB II to CPCB IV+ standard shows the commitment of the Indian government towards environmental sustainability and COP26. Pondering to the stringent emission norms, researchers are exploring various alternate fuels. This has resulted in increased usage of hydrogen as fuel for Internal Combustion Engines (ICE). Leapfrog to hydrogen ICE will take time for the technology and infrastructure to mature, therefore Hydrogen enriched Compressed natural gas (HCNG) is an intermediate solution for de-carbonisation of ICE. HCNG blends take benefit of the unique combustion properties of hydrogen and at the same time reduce the demand for pure hydrogen. HCNG can take advantage of existing investment in natural gas infrastructure and also has much higher volumetric energy storage density than pure hydrogen. In this study, an in-use multi-cylinder NG operated CPCB II compliant Genset engine was assessed with various HCNG fuel blends. The main objective of the study was to analysis the combustion dynamics and to evaluate the effect of 25HCNG and 30HCNG on the genset engine without major modification in Hardware. The study also draws focus on the combustion parameter variations with higher HCNG blend induction in the engine. With the usage of HCNG the CO, HC pollutants reduce by around 26-46% keeping similar trend of NOx. This approach can make HCNG a probable candidate to reduce emissions from genset engines.
Bandyopadhyay, Debjyoti, Sutar, Prasanna S, Dhar, Rit Prasad, Sonawane, Shailesh Balkrishna, Rairikar, Sandeep D, Thipse, Sukrut S, Singh, Sauhard, Mishra, Sumit Kumar, Bera, Tapan, Badhe, Rajesh, Tule, Shubham, Aghav, Yogesh, Lakshminarasimhan, Krishna
1D Simulation Approach for Common Rail Injection Systems for a Marine 2 Stroke Diesel Engine2026-26-03951/16/2026
This study presents a comprehensive 1D simulation approach of an automotive solenoid-based diesel fuel injector and a common rail injection system for a marine engine using Simcenter AMESim. The injector model was developed to analyse the injection rate and total injected fuel at various solenoid actuation durations (1.2 ms and 2.0 ms) and common rail pressures. The experimental results from a well-established research study are used for validating the simulation results of the solenoid-based injector. Overall error in total fuel injected ranges from -6.14 percent to 1.93 percent, while timing errors for the start of injection vary from 1.7° crank angle (CA) to 0.08° CA and the end of injection from 2.8° CA to 0.20° CA at 1200 rpm demonstrating strong agreement at higher rail pressures (above 1000 bar) and solenoid actuation times. Building on this validated injector model, a detailed marine common rail system was developed incorporating key hydraulic components: a check valve to maintain pressure inside the rail, flow limiting valves to prevent overpressure in the fuel injector, and a combination pressure relief valve. The simulation was used to study rail pressure dynamics at 50 percent of the engine load for varying rail lengths, diameters, and injector flow rates. The experimental results for the common rail pressure test match closely with the simulated common rail pressure dynamics. Parametric studies reveal sensitivity of rail pressure to geometric variations, which in turn influence injection characteristics. The developed model serves as a useful tool for assessing design changes in high-pressure injection systems and optimizing performance in marine engine applications.
Bhoware, Yash, Pise, Uday, Saha, Dipta, Gaikwad, Nilesh
Material Compatibility Studies of Ethanol Blended Diesel2026-26-01291/16/2026
The Government of India has mandated biofuel blending in automotive fuels to reduce crude oil imports and support the national economy. As part of this initiative, Oil Marketing Companies (OMCs) have begun nationwide blending of E20 fuel (20% ethanol in petrol). Ethanol supply is expected to exceed demand by the end of 2025 due to initiatives like the Pradhan Mantri JI-VAN Yojana. Alternative applications for ethanol are being explored; one promising approach is its use as a co-blend with diesel fuel (ED blends). However, ethanol’s low cetane number and poor lubricity pose challenges for direct use in diesel engines without modifications. ED blends demonstrated reduced emissions while maintaining performance comparable to conventional diesel. To further address concerns related to materials compatibility of ED blends with fuel system components, particularly plastomers that may impact engine durability, a detailed study was conducted using elastomers such as FVMQ, FKM, HNBR, and NBR in accordance with the SAE J1748. Test specimens were immersed in ED blends and conventional diesel at 55°C for 1008 hours. Key physical and mechanical properties were measured before and after the immersion tests. The results revealed that FVMQ, FKM and HNBR demonstrated comparable durability when exposed to ED blends vis-à-vis diesel, whereas NBR performed better only in conventional diesel. SEM analysis of the specimens showed significate surface degradation in NBR, supporting the mechanical test results. Although ED blends exhibited changes in fuel properties such as flash point and water content, the blends remained stable under ambient storage conditions.
Johnpeter, Justin P, Chakrahari, Kiran, Chakradhar, Maya, Arora, Ajay, Prakash, Shanti, Pokhriyal, Naveen Kumar
A Study on Combustion Process in Hydrogen/Hydrotreated Vegetable Oil Dual-Fuel Operation Using Hydroxyl Radical Chemiluminescence03-18-08-00501/7/2026
This study investigated the combustion processes in hydrogen dual-fuel operation using hydrotreated vegetable oil (HVO) and diesel fuel as pilot fuels. The visualizations of hydrogen dual-fuel combustion processes were conducted using hydroxyl radical (OH*) chemiluminescence imaging in an optically accessible rapid compression and expansion machine (RCEM), which can simulate a compression and expansion stroke of a diesel engine. Pilot injection pressures of 40 and 80 MPa and injection quantities of 3, 6 mm3 for diesel fuel and to match the injected energy, 3.14, 6.27 mm3 of HVO were tested. The total excess air ratio was kept constant at 3.0. The RCEM was operated at a constant speed of 900 rpm, with in-cylinder pressure at top dead center (TDC) set to approximately 5.0 MPa. Results demonstrated that using HVO as pilot fuel, compared to diesel fuel, led to shorter ignition delay and combustion duration. OH* chemiluminescence imaging revealed that longer ignition delays observed with diesel fuel resulted in pilot mixture ignition downstream near the piston bowl wall, followed by flame propagation into the hydrogen–air mixture. In contrast, the shorter ignition delays characteristic of HVO caused the pilot mixture to ignite between the injector and the piston bowl wall, with subsequent flame propagation into the hydrogen premixture.
Mukhtar, Ghazian Amin, Une, Naoto, Horibe, Naoto, Hayashi, Jun, Kawanabe, Hiroshi, Hiraoka, Kenji, Koda, Kazuyuki
Numerical Simulation of Additized Ethanol: Impact of Engine Parameters on Combustion, Performance and Emissions2025-36-025012/18/2025
One alternative to fossil fuels is the use of bioethanol in internal combustion engines. However, the application of this renewable fuel in compression-ignition engines is limited due to its low cetane number. This barrier, however, can be overcome by using additives that enhance this property. Consequently, additized ethanol emerges as a promising option with significant potential for decarbonization and improved combustion efficiency. In this context, the present study numerically investigated, using the CONVERGE CFD software, the use of additized ethanol in a compression-ignition internal combustion engine used in marine transportation. As a comparative baseline for each investigated setup, cases involving conventional diesel fuel were also analyzed numerically. The reaction mechanisms used for modeling the combustion of both additized ethanol and conventional diesel were validated against experimental data available in the literature. Di-tert-butyl peroxide (DTBP) was the studied cetane improver used in this study, blended with ethanol at weight fractions equal to 0%, 5% and 10%. In addition to the additive content in ethanol, the study also evaluated, through a sensitivity analysis, the impact of fuel injection strategies, including variations in injection timing (from 6 to 0 degrees before top dead center) and engine load levels (25%, 50%, 75%, and 100%). Key combustion, performance, and emission parameters were analyzed, including ignition delay, heat release rate, thermal and combustion efficiency, and emissions of CO₂, CO, NOX, CH4 and CO2eq. The results indicate that additized ethanol is a viable fuel for compression-ignition engines.
Assis, Guilherme, Sánchez, Fernando Zegarra, Pradelle, Renata Nohra Chaar, Braga, Sergio Leal, Ticona, Epifanio Mamani, Souza Junior, Jorge, Pradelle, Florian
Experimental Investigation of Additive Formulations for Ethanol Use in Compression Ignition Engines Using a Rapid Compression Machine2025-36-018512/18/2025
The transition to renewable fuels is critical to reduce greenhouse gas emissions and achieve carbon neutrality in the transportation sector. Ethanol has emerged as a promising biofuel for compression ignition (CI) engines due to its renewability and low-carbon profile. However, its low cetane number, high latent heat of vaporization, poor lubricity, and corrosive properties severely limit its auto-ignition capability and durable operation under conventional CI conditions. Building upon previous work using a Rapid Compression Machine (RCM) to assess ignition improvers for ethanol, this study explores a broader range of fuel formulations to enhance ethanol-based combustion. A total of nine blends were prepared, consisting predominantly of hydrated ethanol (50-80% by volume), combined with 5-25% biodiesel and up to 5% of a commercial ignition improvers. The biodiesel component acted both as a co-solvent and as a combustion stabilizer, particularly under cold-start conditions. Tests were carried out under both hot and cold-start conditions, across compression ratios ranging from 25:1 down to the ignition failure limit. To ensure equal injected energy input, injected fuel mass was adjusted based on the Lower Heating Value (LHV) of each blend. High-resolution pressure transducers and high-speed optical imaging were employed to provide direct experimental insights into the combustion process, validate thermodynamic trends, and support comparative assessments of ignition behavior across different blends and compression ratios to evaluate key combustion parameters. The results indicate that blends enriched with both biodiesel and ignition additives, particularly E900B50A50, E925B50A25, and E925B25A50, significantly improved auto-ignition performance, enabling complete and stable combustion under compression ratios higher than 23. Uniform flame front propagation was observed across all injector nozzles, indicating complete combustion and effective fuel–air mixing, which are essential for maximizing thermal efficiency and minimizing unburned emissions in CI engine operation.
Bacic, Denise Amato, Sánchez, Fernando Zegarra, Ticona, Epifanio Mamani, Pradelle, Renata Nohra Chaar, Santos Coelho, Lucas dos, Mota, Crislane Almeida Pereira da, Pradelle, Florian
Mixing Rules for Accurate Prediction of Physicochemical Properties in Automotive Diesel-Biodiesel-Ethanol Blends2025-36-013512/18/2025
The increasing demand for reduced emissions in the automotive sector has driven research into alternative fuels, including Diesel, Biodiesel, and ethanol blends. This study aims to optimize mixing rules to predict the physicochemical properties of ternary fuel blends, essential for improving engine performance and minimizing emissions. Seven established mixing rules—Kay’s Equation, Semilogarithmic Equation, Grunberg-Nissan Equation, Modified Lederer Equation, Hu-Burns Equation, Power Law, and Polynomial Equation—were evaluated to estimate key properties such as kinematic viscosity, cetane number, cetane index, flash point, pour point, and cloud point. A comprehensive database, sourced from previous literature, included pure fuel properties and blend data for 33 to 101 cases. MATLAB was used to implement nonlinear optimization, adjusting coefficients to minimize error metrics like Mean Absolute Error (MAE), Mean Absolute Percentage Error (MAPE), and Standard Deviation (SD). The physical consistency of the correlations was verified by ensuring that estimated properties followed expected trends. The results identified the best-performing equation for each property, with the Grunberg-Nissan equation providing reliable estimates for viscosity and cetane number, and the Hu-Burns equation excelling in cetane index and cloud point. Additionally, the polynomial equation demonstrated accuracy for flash point. The optimized correlations were validated with independent experimental data, confirming their robustness and suitability for automotive fuel applications. This approach simplifies the selection of fuel compositions, contributing to cleaner fuel formulations and supporting the shift towards sustainable energy solutions.
Tirado, Carlos Andrés Abanto, Lobato, Maria Letícia Costa, Passos, Sthefany Faber, Pradelle, Renata Nohra Chaar, Pradelle, Florian
Ignition Delay and Combustion Efficiency Analysis of Marine Diesel-Biodiesel-Ethanol Blends in a Rapid Compression Machine2025-36-013112/18/2025
In alignment with the International Maritime Organization’s 2023 GHG Strategy and the Paris Agreement, this study investigates the viability of ternary blends of marine diesel, biodiesel, and ethanol as low-emission marine fuels. While previous studies have established the physicochemical behavior and storage stability of such blends, particularly the co-solvency role of biodiesel to prevent phase separation, limited data exists on their combustion performance under engine-relevant conditions. This work addresses this gap through a series of controlled experiments conducted in a Rapid Compression Machine (RCM), which enables the approximate a single-cycle combustion in a compression ignition engine. The tested blends included varying proportions of ethanol (up to 20% in volume) in a blend of fossil fuel with 25% of biodiesel (25%), and their combustion were evaluated across different injection timings. Key performance metrics such as ignition delay, maximum temperature and pressure, thermodynamic efficiency, and combustion efficiency were calculated and analyzed. Results demonstrated that increasing ethanol content led to longer ignition delays due to ethanol’s low cetane number and high latent heat of vaporization, which in turn affected heat release dynamics and efficiency. Thermodynamic efficiency peaked at early injection timings, reaching up to 49.41% for B25E20 blends with intermediate timing (3 mm), while combustion efficiency also improved with higher ethanol content, especially at early and late injection points. Notably, B25E20 achieved the highest combustion efficiency among all blends tested and for all injection timing. These findings highlight the potential of biodiesel–ethanol–diesel blends for reducing maritime emissions while optimizing energy utilization, provided that injection parameters are carefully tuned. The study also reinforces the need for further refinement of predictive models to capture the nonlinear behavior of these fuels, supporting the broader transition to sustainable marine propulsion technologies.
Lobato, Maria Letícia Costa, Sánchez, Fernando Zegarra, Ticona, Epifanio Mamani, Pradelle, Renata Nohra Chaar, Braga, Sergio Leal, Coelho, Lucas Dos Santos, Pradelle, Florian
In-Flight Evaluation of Sustainable Hydrocarbon Fuels in Compression Ignition Aircraft Engines2025-01-053311/25/2025
As global air traffic is expected to increase significantly in the coming decades, reducing the associated climate impact requires scalable solutions. While alternative propulsion technologies such as electric and hybrid-electric systems might offer long-term potential, their current applicability remains limited due to low energy density, limited range and scalability, and system complexity. Consequently, thermodynamic propulsion systems – such as gas turbines and piston engines – are expected to remain dominant in the medium term. In this context, sustainable hydrocarbon-based aviation fuels represent a practical and necessary solution. Certified sustainable aviation fuel (SAF) pathways are currently approved exclusively for use in gas turbines, with certification standards tailored to turbine-specific requirements. Consequently, fuel properties such as cetane number and evaporation behavior are not included in existing specifications. However, when SAF-kerosene blends are used in compression ignition engines, the impact of these properties on ignition quality, combustion behavior, and emissions must be specifically evaluated. For this purpose, a flight test campaign was conducted using a fully instrumented Diamond DA42 aircraft, configured as a flying laboratory and equipped with serial-production piston engines. Two synthetic fuel variants were evaluated: one certified according to ASTM D7566-23a Annex A2 (HEFA SPK) and a second, Tall Oil derived fuel with a distinctly different molecular composition – characterized by an increased content of cycloparaffins and low aromatics content. The aircraft as a flying air lab was equipped with special engine measurement technology including high-pressure in-cylinder indication to analyze the impact of these differing fuel compositions on engine efficiency and combustion characteristics, including ignition delay and peak pressure. Furthermore, a mobile emission and particle number measurement system enabled the assessment of environmental performance under real flight conditions. Both fuels demonstrated significant reductions in thermal NOx formation due to their low aromatics content. However, no clear benefit was observed in total particle number (PN), likely due to a shift in the particle size distribution towards the nanoparticle regime.
Kleissner, Florian, Hofmann, Peter, Vogd, Philipp, Vauhkonen, Ville, Käkölä, Jaana, Greve, Alina
Comparative Analysis on the Characteristics of Palm Biodiesel–Diesel Blend–Powered Compression Ignition Engine Using Novel Dimensionless Index04-19-02-000711/20/2025
In this study, a Kirloskar TV1 compression ignition engine is put to test using diesel, palm biodiesel (B100), and palm biodiesel–diesel blend (B40D60). Among the tested fuels, engine performance at 75% loading condition with reference fuel diesel showed the highest brake thermal efficiency, brake specific energy consumption, and exhaust gas temperature at 27.78%, 12.96 MJ/kWh, and 335.88°C, respectively. While B100 and B40D60 were observed to give a lower value for the same parameters due to their inferior physiochemical properties. In terms of combustion pressure, mean gas temperature, rate of heat release, and rate of pressure rise, the values observed with B40D60 at 67.39 bar, 1397.76 K, 68.83 J/CAD, and 4.34 bar/CAD, correspondingly are better than B100 due to the presence of diesel. Yet for the same combustion parameters, the values for both the aforementioned fuels are still lower than the results seen with pure diesel fueling. Owing to higher cetane number in comparison to diesel for B100 and B40D60 resulted in a lower ignition delay value of 8 and 10, respectively. However, an inverse trend was recorded for combustion duration, where diesel attained the shortened duration of 35 CAD in comparison to B40D60 and B100. A novel benchmark known as Rationalized Engine Characteristic Quality Index was developed, which considers various parametric indicators. The dimensionless index score for diesel was observed to be 0.779, which is higher than B100 and B40D60 at 0.754 and 0.756, respectively. It can be attributed to better physiochemical properties and engine performance characteristics when using petroleum diesel.
Balakrishnan, Navaneetha Krishnan, Chelladorai, Prabhu, Muhammad, Syahidah Akmal
A Comprehensive Study on the Effect of Compression Ratio and Pilot Injection Strategy on Alcohol Compression Ignition03-18-07-004411/13/2025
Achieving compression ignition (CI) with ethanol, a renewable fuel, comes with challenges because of its much lower cetane number compared to diesel. Additionally, ethanol’s high cooling potential and high volatility compared to diesel also offer challenges and opportunities to achieving robust, high-efficiency CI. Increasing the compression ratio (CR) and expanding the injection strategy beyond a conventional close-coupled pilot-main diesel injection strategy can help overcome these challenges. This work experimentally tested ethanol CI with several different injection strategies with CRs ranging from 16.3 to 22.3. The results showed that in homogeneous charge CI (HCCI), increasing the CR improved thermal efficiency but incurred a combustion efficiency penalty. In any CI concept, increasing the CR lowered the required intake temperature to achieve ignition. Using close-coupled pilot injections is an effective way to achieve ethanol CI, but it was also shown that HCCI-like intake stroke “pilot” injections offer a new avenue of ethanol CI. With a 25% pilot injection during the intake stroke, stable ethanol CI was achieved at 6 bar IMEPg with an intake temperature of 330 K using a CR of 20.0. There was a ~1 percentage point thermal efficiency benefit and ~50% reduction in NOx, though there was also a 1 percentage point combustion efficiency penalty. At lower loads, it was more beneficial to run with more fuel in the intake stroke pilot. Finally, experiments showed that the NOx emissions decreased from 5.75 g/kWh to 3.43 g/kWh at 6 bar IMEPg by increasing the CR from 16.3 to 20.0 and reducing the intake temperature by 60 K. Even with matched intake temperature, the engine-out NOx was 4.57 g/kWh with a CR of 20.0. CFD simulations showed that this was due to the higher CR having a more rapid expansion process, cooling the diffusion flames more rapidly.
Gainey, Brian, Vedpathak, Kunal, Kumar, Mohit, Lawler, Benjamin
Performance and Emission Characteristics of CI Engines Using Ethanol- Cottonseed Biodiesel Blended with Aluminum Oxide Nanoparticles2025-28-021011/6/2025
As global energy demands continue to grow and environmental challenges intensify, Biodiesel stands out as an environmentally sound and technically feasible alternative to curb fossil fuel use and emissions. This study provides an in-depth analysis of the performance and emissions profile of a compression ignition (CI) engine running on a renewable diesel fuel blend made from ethanol and cottonseed (Cs) combinations enhanced with aluminium oxide (Al2O3) nanoparticles. The experimental fuel blends, consisting of 10%, 20%, and 30% cottonseed biodiesel with 5% ethanol and remaining with conventional diesel, were analyzed under varying engine load conditions. The inclusion of ethanol improved fuel atomization due to its lower viscosity and higher volatility, while Al2O3 nanoparticles acted as advanced combustion catalysts, promoting enhanced oxidation rates and thermal efficiency. Among the blends, B10 (10% cottonseed biodiesel) exhibited superior performance metrics, achieving a brake thermal efficiency (BTE) of 32.8%, marginally below diesel’s 33.44%, and a 1.6% rise in brake-specific fuel consumption (BSFC). The analysis of emissions highlighted a considerable decline in nitrogen oxide (NOₓ) emissions. 7.14%, 10.71%, 14.29% recorded for B10, B20, B30 blends respectively. Carbon monoxide (CO), unburned hydrocarbons (HC), and smoke opacity showed a small uptick. The overall emissions profile confirmed substantial environmental benefits, establishing B10 as the most balanced blend for optimized engine performance and minimized pollutant emissions. This research paves the way for future developments in renewable biodiesel blends, offering advancements in fuel economy, cleaner combustion, and overall emission reductions, while addressing the increasing demand for sustainable energy sources.
T, Karthi, G, Manikandan, Saminathan, Sathiskumar, M E, Chandhuru, S, Bavanya, S, Arunkumar
Fuel Differentiation for Energy Efficiency in Heavy-Duty Diesel Applications: A Case Study for the Determination of Exhaust Emissions and Fuel Economy2025-28-023111/6/2025
For the achievement of Net Zero Emission goals, various corporates have started with the planning towards the achievement of short-term goals which are well defined with the implementation of energy conservation and efficiency. In this direction, high cetane diesel is an optimized combination of diesel fuel with higher Cetane Number fortified with Novel & Optimized multi-functional additives (MFAs) formulation for improved performance and specially designed for heavy duty diesel engines & off-highway applications. This innovative concept is based on enhancement of fuel economics by enhancement in fuel combustion, injector cleaning characteristics and reduction of frictional losses. The benefits associated with high cetane diesel include superior cleanliness to keep high pressure diesel injectors clean, better lubricity providing longer injector life, superior combustion leading to lower noise and products formulated for benefits in overall reduction in emissions specially developed for Heavy Duty Applications. The fuel guzzlers in the mining sectors are struggling with the fuel efficiency and the high cetane diesel validation was explored deploying an indigenous test procedure which compared the performance of dumper in various operational conditions and determined the fuel consumption for BSVI diesel as well as high cetane diesel. The methodology and test protocol were developed suiting to the application involved for the heavy-duty applications and instrument set-up was amply suiting to the test requirements. For the determination of fuel consumption and efficiency, in-line fuel consumption meter and portable emission measurement device were used at the mining location. In the present study, the emission reduction and fuel consumption achieved with high cetane diesel and the measurements along with the results are described. The average reduction in fuel consumption with high cetane diesel was 4.303%, with emissions reductions of CO (3.72%), THC (5.29%), NOx (5.05%) and CO2 (4.08%). This product represents a game changer concept for India’s commitment towards net zero emissions by 2070 and carbon intensity reduction by more than 45 percent by 2030.
Kumar, Prashant, Mayeen, Hafiz, Saroj, Shyamsher
Experimental Study on Single Cylinder Diesel Engine Port Water Injection and Blends of Biodiesel for Performance & Emission2025-32-006211/3/2025
The increasing demand for alternative fuels due to environmental concerns has sparked interest in biodiesel as a viable substitute for conventional diesel. Most automotive engines use diesel fuel engines. They contribute a major portion of today’s air pollution, which causes serious health issues including chronic bronchitis, respiratory tract infections, heart diseases, and many more. Greenhouse gases are produced using fossil fuel in the engines and causes global warming. To combat air pollution, we need clean renewable and environmentally friendly fuels. Due to depletion of fossil fuels, it has become necessary to find alternative fuel which are safer for the environment and humankind. One such possible solution is Biodiesel. In present study, series of experiments were carried out on 435cc naturally aspirate DI Diesel engine with port water injection and different blend of Jatropha based Biodiesel. Biodiesel was derived from Jatropha oil, produced using a heterogeneous catalyst. The physical and chemical properties were determined for different blends of Biodiesel specifically JB20, JB30 and JB100 before engine testing. Engine tests were recorded on engine eddy current dynamometer and vehicle emission were recorded on chassis dynamometer to investigate the performance and emission characteristics of different biodiesel blends compared with conventional diesel. Recorded engine test performance infers improvement in observed torque and power. BSFC and Smoke results were comparable on full load and part load conditions. There is reduction in HC, CO raw emission with JB20 and JB30 Biodiesel fuel as compared to conventional Bharat Stage 6 Diesel fuel. Particulate Matter are comparable with all the above fuels. Vehicle mass emission with combination of port water injection and JB20 biodiesel has benefited further to reduce HC & NOx emission to meet Bharat Stage 6 emission norms on Diesel three-wheel vehicle on Indian Driving cycle. These findings highlight the potential of Jatropha biodiesel as a cleaner alternative to conventional diesel.
Bhoite, Vikram, Syed, Kaleemuddin, Chaudhari, Sandip, Khairnar, Girish, Jagtap, Pranjal, Reddy, Kameswar
Hydrogen-Assisted Renewable Fuels RME and HVO in the Compression-Ignition Engine2025-32-004811/3/2025
The article presents the research results on performance, thermodynamic parameters, and toxic exhaust emissions from the combustion in a compression-ignition engine fueled optionally by the hydrotreated vegetable oil (HVO) or the rapeseed methyl ester (RME), both with hydrogen addition. Furthermore, regular diesel fuel was used to obtain the reference data for making comparisons between HVO, RME, and diesel fuel. Hydrogen was injected into the intake manifold of a compression-ignition (CI) engine. Typically, diesel fuel combustion in a CI engine initiates through its self-ignition, usually simultaneously occurring at many points across the engine cylinder. Hydrogen, as a very chemically reactive substance, can promote pre-ignition reactions and accelerate flame kernel formation, shortening the ignition lag. This is crucial for the smooth running of the compression-ignition engine. Hydrogen was added at amounts not exceeding 7% by volume (35% energy content) referred to air sucked into the engine cylinder. As observed, a slightly positive trend in NOx vs. hydrogen addition was observed. It was also found that hydrogen added in small amounts does not form the so-called knock originating from hydrogen rapid combustion, regardless of the diesel knock.
Szwaja, Stanislaw, Juknelevicius, Romualdas, Pukalskas, Saugirdas, Rimkus, Alfredas, Szymanek, Arkadiusz
Impacts of Hydrotreated Vegetable Oil as Renewable Diesel Fuel on Engine Performance and Emissions in a Heavy-Duty Diesel Engine03-18-06-00359/8/2025
As the pressure increases to move to renewable carbon-neutral fuel sources, especially in heavy-duty diesel engine applications, hydrotreated vegetable oil (HVO) has shown to be an attractive alternative fuel to fossil diesel. Therefore, this study investigated the impacts of HVO used as a drop-in fuel on performance and emissions of a nonroad heavy-duty diesel engine by running back-to-back D2 ISO 8178 cycles with ultra-low sulfur diesel (ULSD) and HVO. The measurement results showed that brake specific fuel consumption with respect to mass reduced by 1.1%–3.6% switching from ULSD to HVO due to greater heating values of HVO, which is supported by 0.7%–3.5% lower CO2 emissions recorded with HVO. Conversely, brake specific fuel consumption with respect to volume increased by 0.3%–2.9% with HVO because of its smaller density. Combustion analysis revealed that combustion of both fuels is comparable at high loads while HVO ignites earlier at low power. Thus, lesser reductions in NOx emissions (0%–6%) were observed at high loads, which can be attributed to lower combustion temperatures of HVO. On the other hand, higher cetane number of HVO at low loads resulted in notable reductions in NOx (36%–39%). Advanced start of HVO combustion at low power caused an increase in PM, soot, and smoke. At high to mid loads, PM, soot, and smoke decreased by 18%–55% because HVO is fully paraffinic, has higher H/C ratio compared to ULSD, and contains no sulfur or other mineral impurities. With greater reduction at low loads, HC and CO were lower for HVO due to its non-aromatic content, high cetane number, lower distillation curve, lower density, and smaller viscosity. Overall, it is concluded that HVO can play an important role as a sustainable fuel source for transportation and power production in the coming decades.
Duva, Berk Can, Abat, Bryan, Engelhardt, Jens
Model-Based Optimization of Diesel/OMEx Fuelled CI Engine under Multiple Blending Conditions2025-24-00389/7/2025
The search for alternative solutions for vehicle electrification, while reducing the carbon footprint during the transition to green mobility, leads to the investigation of electro-fuels (e-fuels) in conventional internal combustion engines. Leveraging previous research, the present study focuses on the optimisation of a Compression Ignition (CI) engine combustion control in response to the use of the Oxymethylene Dimethyl Ethers (OMEx) blended with conventional diesel. The selected e-fuel is the OME3, which is expected to be used as a drop-in solution and to easily achieve a reduction in soot emissions due to both its high oxygen content and lack of direct carbon bonds in its molecular structure. To verify its potential, a 1D single-cylinder CI multi-zone engine model has been exploited to simulate various diesel/OME3 blends in a wide engine operating range. The first step deals with the evaluation of performance and emissions to demonstrate the differences, particularly in terms of emissions reduction compared to the baseline standard configuration. Each operating condition is then optimized to minimize the energy losses associated with fuel substitution while maintaining the beneficial emission reductions. The model parameters identification and the optimisation of the different blends for each engine operating point are carried out using the software GT-Suite. This approach aims to provide an assessment of the methodology to design new control strategies along with the analysis of the potential impact of using such blends. On the basis of these results, a further optimization was carried out to assess, for each optimized operating point, which blending ratio guarantees the best performance both in terms of emissions and fuel consumption.
Foglia, Antonio, Cervone, Davide, Frasci, Emmanuele, Arsie, Ivan, Polverino, Pierpaolo, Pianese, Cesare
Mid-IR Laser Extinction Measurements of Formaldehyde Emissions in a Methanol Mixing-Controlled Compression Ignition Engine2025-24-00349/7/2025
As energy security and sustainability becomes important, the role of alternative fuels, particularly methanol, is becoming increasingly significant. While the feasibility of methanol as a substitute for diesel fuel has been explored, understanding of emissions from methanol-fueled compression-ignition engines remains limited, even though these engines are known to emit formaldehyde (CH2O) due to methanol’s chemical structure and oxidation pathways. In this study, a quantitatively measurable mid-IR laser-based extinction methodology was employed to understand CH2O formation in a methanol mixing-controlled compression ignition (MCCI) engine. Stable methanol MCCI combustion was achieved with the addition of 5%vol 2-ethylhexly nitrate (EHN) and by using a triple injection strategy (pilot + pilot + main), and CH2O emissions were measured with high temporal resolution by laser extinction while sweeping the injection timing. In addition, the injection strategy was systematically varied by enabling and disabling different injection events to investigate the effect of pilot and main injections on CH2O formation. Injection timing sweeps revealed that CH2O emissions did not monotonically increase with retarded injection, as carbon monoxide did. This decoupling suggests that CH2O formation is not governed solely by global combustion inefficiencies but is instead tied to localized mixture conditions and oxidation pathways. Cycles with elevated CH2O emissions featured minimal low-temperature heat release of pilot injections and, subsequently, more retarded combustion phasing. This indicates that combustion quality of pilot injections strongly affect engine-out emissions, and suggests that overly lean mixtures created by pilot injections promote CH2O formation when later exposed to high-temperature heat release (HTHR). Injection strategy modulation showed that the absence of HTHR results in minimal CH2O emissions, even when large amount of fuel were injected, emphasizing HTHR’s role in initiating methanol oxidation and CH2O formation. In contrast, strategies promoting lean mixtures followed by HTHR led to higher CH2O emissions due to incomplete oxidations. Additionally, acetaldehyde (CH3CHO) emissions were consistently detected. Chemical kinetic simulations revealed that CH3CHO forms through unimolecular decomposition of EHN-derived intermediates or secondary reactions between methanol and species derived from EHN oxidation like C2H5O2. These results offer new insight into the oxidation behavior of methanol under MCCI conditions and highlight the role of thermal and chemical stratification in pollutant formation.
Lee, Sanguk, Lopez Pintor, Dario, Narayanan, Abhinandhan
Study of a CI Engine for Off-Road Application in Diesel-Hydrogen Dual Fuel Configuration2025-24-00559/7/2025
Hydrogen as fuel in internal combustion engines is a promising solution for reducing greenhouse gas emissions, as its combustion produces only water vapor. One potential application is in dual fuel (DF) engines, where diesel is used to ignite the mixture, and hydrogen serves as the primary fuel. However, there is limited literature on the use of hydrogen in compression ignition (CI) engines for off-road applications running in dual fuel diesel/hydrogen, which motivates this study. The focus is on a 3-cylinder, 1-liter naturally aspirated (NA) engine with a compression ratio of 17.5:1 equipped with direct injection (DI) for diesel. Retrofitting the engine with 3 port fuel injectors, it was possible to feed the engine with hydrogen by the control system elaborated in the laboratory. The study aims to analyze dual fuel diesel/hydrogen combustion characteristics and the emissions across different engine speeds (from 1600 rpm to 3600 rpm) and loads (30%, 50% and 70%). The dual fuel operation was done by using 10% of the maximum load provided by diesel, and the overall load is adjusted by increasing the hydrogen amount. Engine load was managed up to a premixed ratio between 39% to 65% of energy provided by hydrogen, depending on the engine speed. The results indicate that the premixed charge of hydrogen burns differently, driven by diesel fuel. This behavior depends on the effective excess of air in the engine. Comparing the emissions in dual fuel configuration where 10% of the load is provided by diesel and diesel operation at the same engine power, CO2 and NOx emissions decrease up to 57% and 61%, respectively, for 70% load. On the other hand, particulate matter (PM) increases up to 77%, at 50% load; it can depend on the worsening of mixing and combustion of the main injection and less production but also less oxidation of the soot.
Gelé, Raphaël, Mancaruso, Ezio, Rossetti, Salvatore, Rousselle, Christine, Brequigny, Pierre
Experimental Investigations on the Effects of Injector Orientation in a Diesel-Gasoline-Fuelled Premixed Charge Compression Ignition Engine2025-24-00439/7/2025
Premixed Charge Compression Ignition (PCCI) presents a promising alternative to conventional diesel combustion (CDC), offering significant reductions in pollutant emissions by lowering local in-cylinder temperatures and enhancing fuel-air mixing. However, a significant challenge in implementing PCCI is controlling the start of combustion, especially given its narrow operating load range. This is primarily due to early ignition and knocking combustion at higher loads when using high-reactivity diesel fuel, which limits the practical applicability of PCCI mode in diesel engines. In the present study, experimental investigations are carried out on a light-duty diesel engine operating in PCCI mode using two fuel blends: 10% (D90G10) and 20% (D80G20) gasoline mixed with diesel on a volume basis. To facilitate combustion control and emission reduction, exhaust gas recirculation (EGR) and water vapor are used as charge diluents. A common rail direct injection (CRDi) system replaces the conventional mechanical fuel injection system, and the engine's compression ratio is reduced from 17.5 to 15 to enable PCCI operation. Initial parametric studies revealed that early direct injection combined with high injection pressure limited the PCCI operating load range to 30% of the rated load when using diesel fuel. However, incorporating EGR with diesel extended this load range to 60%, albeit with increased unburnt hydrocarbon (HC) and carbon monoxide (CO) emissions. To address these challenges, the engine's cylinder head was modified to accommodate a vertically oriented injector, and diesel was replaced with diesel–gasoline blends. Experiments were then conducted using the modified cylinder head at a constant engine speed of 1500 rpm, under varying load conditions and injection timing, to analyze the effects of injector orientation and fuel blends in combination with EGR and water vapor as charge diluent. The results indicate that the diesel–gasoline blends increase ignition delay and enhance fuel-air mixing time between the end of fuel injection and the start of combustion. Specifically, with the G20D80 blend and combined EGR and water vapor dilution, the engine's operating load range was extended to 74% of the rated load. Compared to the CDC, emissions of NOx and soot were significantly reduced. Additionally, HC and CO emissions were reduced by 11.2% and 43.2% at 60% loads, and smoke was reduced by 57.6%, compared to the baseline PCCI, using EGR and water vapor as charge diluents with D80G20 fuel blends.
Ranjan, Ashish Pratap, Krishnasamy, Anand
CFD-Driven Optimization of Diesel Injection for a Hydrogen-Diesel Dual Fuel Engine2025-24-00459/7/2025
Among the alternatives to the use of fossil diesel fuel, dual fuel combustion, leveraging hydrogen as the low-reactivity fuel, represents a promising approach for both reducing pollutant emissions and improving brake thermal efficiency. In addition, this innovative combustion mode requires minimal modifications to the existing Diesel engines architecture. This study was conducted on a Diesel engine (naturally aspirated, 3-cylinder, 1 L, direct injection), properly modified by the authors to operate in dual fuel mode with port fuel injection of hydrogen. A set of experimental data was used to calibrate the 1D and the 3D-CFD models for both Diesel and diesel-hydrogen dual fuel configurations. The AVL FIRE M 3D-CFD software was employed to model diesel injection and combustion, while the gas exchange process was analyzed by GT-Power. The validated 3D-CFD model was then leveraged to optimize the baseline diesel injection strategy in dual fuel mode, minimizing diesel consumption while maintaining stable combustion and comparable performance with respect to the baseline Diesel engine. Notably, the analysis highlights that, at low loads, where hydrogen energy fraction is limited, a diesel injection strategy consisting of two fuel pulses is required to ensure stable ignition. However, as the hydrogen contribution increases, the main injection can be reduced or eliminated, with the pilot injection alone being sufficient to ignite the premixed charge, without compromising engine efficiency. This optimized strategy enabled a simultaneous reduction in diesel usage, up to −62.6%, and a marked decrease in emissions, with the best reductions reaching −62.5% for CO₂, −81.1% for CO, and −31.6% for NOₓ.
Rinaldini, Carlo, Pisapia, Alfredo Maria, Scrignoli, Francesco, Volza, Antonello, Rossetti, Salvatore, Mancaruso, Ezio
Lignin as Cetane Booster for Methanol and Ethanol2025-24-00759/7/2025
Low carbon, though poorly igniting (i.e., low cetane) fuels, such as methanol, ethanol, and ammonia, are gaining momentum in the maritime fuel market. The most adopted strategy to address the fact that these fuels will not, under typical two-stroke marine engine conditions, auto-ignite, is to co-inject a pilot fuel, such as (very) low sulfur marine fuel oil, which does auto-ignite and furthermore doubles as a spark of sorts for the poorly igniting base fuel. This so-called dual-fuel approach is costly and cumbersome. Cetane boosters are known to improve ignitability of alcohol fuels to the point that a pilot fuel is no longer required. In our earlier research, we found some indication that lignin model compounds could likewise improve the ignitability of alcohols. This paper builds further on this hypothesis, now using commercially available lignin rather than model compounds. Auto-ignition behavior of methanol and ethanol was investigated with up to 10 wt% of therein solubilized lignin in both an Advanced Fuel Ignition Delay Analyzer (AFIDA) and (two-stroke) spray combustion chamber. The results suggest that lignin indeed improves the ignitability of both alcohols and that pilotless auto-ignition is possible under realistic two-stroke marine engine conditions when 10% of (alcohol-soluble) lignin is blended into ethanol, with the associated cetane number being close to 10.
Sementa, Paolo, Tornatore, Cinzia, Catapano, Francesco, Lazzaro, Maurizio, Iannuzzi, Stefano, Kouris, Panos, Boot, Michael
Zero-Carbon Port Fueling for Heavy Propulsion through a Recuperated Split Cycle Engine2025-24-00449/7/2025
Upcoming global emissions regulations demand innovation in heavy-duty road and marine transport. This research explores emissions-compliant concepts using both experiments and simulations focused on the Recuperated Split Cycle Engine (RSCE), which separates compression and expansion to enable internal heat recovery and quasi-isothermal compression. A single-cylinder research engine representing the expansion cylinder of an RSCE demonstrated direct injection diesel and port injection hydrogen co-firing. A validated Chemkin-Pro Multi-Zone model first reproduced, then extended this work, evaluating partial diesel substitution with hydrogen or ammonia alongside secondary working fluids (SWF’s liquid N₂, H₂O, NH₃). For the extension, two variants of the split cycle architecture were employed; the RSCE in combination with hydrogen fueling for the heavy-duty road sector, and the novel recuperated reformed split cycle engine (R2SCE), a new architectural and simulation contribution enabling on-board ammonia reforming and dual-role use of SWFs for the maritime sector. In the RSCE configuration, 10%Vol H₂ with H₂O as SWF delivered 13% NOx and 45% CO₂ reductions, along with a 33% improvement in brake specific fuel consumption (BSFC). System-level evaluation of this configuration demonstrated the potential of Euro 7 compliant NOx with typical after-treatments. In the R2SCE configuration, while SWFs N₂ and H₂O reduced thermal NOx via dilution, the use of NH₃ as a dual role SWF - combined with a Recuperator-Reformer (59% NH₃-to-H₂ conversion) - delivered a 4% increase in total fuel energy and reduced NOx emissions across all tested NH₃ injection levels. The R2SCE system level comparison between 6%Vol NH₃ and diesel-only operation showed 10% and 43% reduction in BSFC and CO₂ per unit work, with NOx within maritime regulatory targets with typical after-treatments. These quantified outcomes serve as reference points for performance benchmarking, demonstrating how, compared to a contemporary conventional engine, the increased flexibility offered by the novel R2SCE concept can maximise fuel-to-power conversion for zero-carbon fuels.
Wylie, Elisa, Panesar, Angad
A Life Cycle Assessment of Potential Pathways to Increase Sustainable Aviation Fuel Yields through CO 2 Upgrading Co-located with Corn Ethanol Production13-06-03-00239/4/2025
Alcohol-to-jet (ATJ) upcycling of ethanol to sustainable aviation fuel (SAF) is an attractive emerging pathway for SAF production, especially in the US Midwest with large-scale corn ethanol production. Only 39% of the corn carbon is converted to ethanol, 20% is emitted as CO2. Capturing the CO2 to produce additional ethanol or SAF directly can increase the carbon yield. To guide technology selection, this work used life cycle assessment for several CO2-to-SAF production pathways. Additionally, improvements for corn ethanol production were explored by replacing natural gas burners with heat pumps for corn drying, which reduced the carbon intensity of corn ethanol by nearly 16%. But subsequent upgrading of the ethanol to SAF is only 4.5–20% better than conventional aviation fuel. By contrast, CO2-based alternative routes to SAF fared better, reducing carbon intensities between 83% and 90%. Gas fermentation of CO2 to ethanol with subsequent ATJ upcycling to SAF was contrasted to Fischer–Tropsch conversion of CO2 to SAF. Both streams require CO2 conversion to CO, which can be produced using reverse water–gas shift or solid oxide electrolyzer cells. The Fischer–Tropsch synthesis shows a higher reduction in carbon intensity (up to 90%) compared to ATJ (up to 84.4%). For other impact categories, such as ozone depletion, ecotoxicity, and the like, the differences are of similar magnitude. Capturing CO2 locally at the bioethanol factory and converting that CO2 to ethanol might overall be preferable with a fermentation process that is quite like bioethanol production compared to Fischer–Tropsch synthesis for which products require a new transportation infrastructure. The aviation fuel yield from ATJ can reach 90%, higher than the 50–70% yield from Fischer–Tropsch synthesis, with gasoline and diesel fuel as major by-products for which markets will shrink in the future. Overall, ATJ appears to be the best choice for CO2-to-SAF using the synergy with corn ethanol factories for quick launch.
McCord, Stephen, Talsma, Sam, Bouchard, Jessey, Zavaleta, Victor Gordillo, He, Xin, Sick, Volker
Experimental and Numerical Insights on Emissions Control with a Diesel Oxidation Catalyst in Reactivity-Controlled Compression Ignition Combustion Conditions03-18-05-00349/1/2025
Reactivity-controlled compression ignition (RCCI), a low-temperature combustion strategy, reduces oxides of nitrogen (NOx) and soot simultaneously; however, high concentrations of carbon monoxide (CO) and total hydrocarbons (THC) and low exhaust gas temperatures pose a significant challenge for the catalytic control of tailpipe CO and THC. Diesel oxidation catalyst (DOC) is generally used in compression ignition (CI) engines for CO, THC, and nitric oxide (NO) oxidation. This work provides a new understanding of the performance characteristics of a DOC in the RCCI combustion strategy with various gasoline–diesel fuel premix ratios ranging from ~46% to ~70% at steady-state operating conditions. Experimental insights from the RCCI strategy prompt considerations of both CO and THC oxidations and THC trap functionalities in the 1D transient model of the DOC. It is observed that an increase in the fuel premix ratio from 50% to 70% in RCCI shifts the CO and THC oxidation characteristics curves by up to 10°C toward low exhaust gas temperatures. The evolution of the catalyst surface temperature with exhaust gas temperature reveals distinct stages of heat transfer, indicating a progressive shift of oxidation reactions from the back to the front side of the DOC channel. Furthermore, axial variations of the oxidation characteristics of the DOC reveal that CO oxidizes over a narrow length of the DOC as compared to THC. Additionally, a nondimensional analysis is carried out to identify kinetic-controlled and mass transfer–controlled regimes of CO and THC oxidations, indicating that both CO and THC are in kinetic-controlled regimes at exhaust gas temperatures lower than 192°C, and transitioning into a mass transfer–controlled regime above this temperature.
Suman, Abhishek, Sarangi, Asish Kumar, Herreros, Jose Martin
Drop-In Performance of Propyl- and Butyl-Terminated Oxymethylene Ethers in a Compression Ignition Engine04-19-01-00037/16/2025
Oxymethylene ethers (OMEs) have been proposed for use in diesel engines as a high-reactivity fuel with reduced soot emission. Historically, the focus on methyl-terminated OMEs has limited drop-in applicability. In this work, a set of extended-alkyl OMEs with methyl, propyl, and butyl terminations are tested in an unmodified 4.5L Deere diesel engine, neat and in various blends with ultra-low-sulfur diesel (ULSD). Engine operability and emissions data are collected for the various fuel blends. External laboratory testing against the ASTM D975 standard demonstrates that a blend of 30% butyl-terminated OMEs with ULSD meets all ASTM standard requirements except lubricity. It is shown that the OMEs and OME–diesel blends demonstrate shorter combustion durations, as defined by the 10%–90% heat release timing, than the ULSD control. Engine brake efficiency is unaffected by OME usage, while specific fuel consumption increases in proportion to the reduced heating values of OMEs. Particulate emissions are reduced to a greater extent for all OMEs and OME blends than the blend ratio would suggest when using the yield sooting index as an estimator. NOx emissions from the OMEs and OME blends are increased with respect to ULSD; however, the increase in NOx is much lower than the decrease in particulates, indicating a possible improvement in the soot/NOx tradeoff seen in combustion engines. Two observed downsides are increases in unburned hydrocarbon and formaldehyde emissions. Overall, butyl-terminated OMEs are recommended for future study as the ideal diesel blendstock studied in this work, with good balance of matching properties and improved emissions performance.
Lucas, Stephen P., Zdanowicz, Andrew, Wolff, Wyatt W., Windom, Bret
Dispenser Nozzle Spouts for Liquid Fuels Intended for Use with Spark Ignition and Compression Ignition EnginesJ285_202507 (Current)7/9/2025
This SAE Recommended Practice provides standard dimensions for liquid fuel dispenser nozzle spouts and a system for differentiating between nozzles that dispense liquid fuel into vehicles with spark ignition (SI) engines and compression ignition (CI) engines for land vehicles. Current legal definitions only distinguish between “Unleaded Fuel” and “All Other Types of Fuel.” These definitions are no longer valid. This document establishes a new set of definitions that have practical application to current automobile liquid fuel inlets and liquid fuel dispenser nozzle spouts.
Fuel Systems Standards Committee
Application of Sustainable Aviation Fuels in Compression Ignition Aviation Engines: In-Flight Investigations2025-01-03177/2/2025
To achieve a significant reduction in net CO₂ emissions in the aviation sector, sustainable aviation fuels (SAFs) are considered a key factor. Current research efforts are therefore focused on SAFs, which exhibit properties that differ from conventional kerosene, particularly in aspects critical to compression-ignition (CI) engines, such as cetane number, evaporation behavior or lubricity. These differences necessitate dedicated investigations to assess their suitability and performance in such engines. However, real operating conditions — such as intake air- and exhaust- pressure levels during flight — cannot be fully replicated on standard engine test benches. For this reason, real flight experiments were conducted to address these limitations. Notably, this work marks the first instance of in-flight testing of SAFs in CI aviation engines, constituting a significant milestone in this research area. In the course of these investigations, ASTM D7566 Annex A2-compliant HEFA (hydroprocessed esters and fatty acids) was tested across a wide range of blend ratios, including pure HEFA. The in-flight tests were performed, using a DA42 aircraft from Diamond Aircraft Industries (DAI), equipped with two AE330 engines from Austro Engine (AE). For safety reasons, one engine was left in its original configuration, while the other one was outfitted with advanced measurement systems, including in-cylinder pressure sensors, a mobile exhaust gas analysis system (portable emission measurement system - PEMS), and various pressure and temperature probes. This setup enabled precise measurement of gaseous emissions, particle number (PN), efficiency, and combustion parameters. The operation of the test engine with HEFA blends, up to and including pure HEFA, was successfully demonstrated. The flight campaign highlighted the emission potential of this aromatics-free fuel. Additional test bench investigations confirmed the findings from the initial flight campaign: while soot mass emission decreased significantly with increased HEFA-share, particle number (PN) remains on a constant level, indicating a shift in the particle size distribution. This emphasizes the importance of understanding the trade-offs and adapting engine calibration when using SAF in CI (aviation) engines.
Kleissner, Florian, Reitmayr, Christian, Hofmann, Peter
An Experimentation of Performance of Compression Ignition Engine Fueled with Nano-alumina–Enhanced Diesel, Diesel–Ethanol, and Diesel–Butanol Blends03-18-04-00276/30/2025
This study is to use the renewable fuels such as bioethanol and biobutanol as performance-improving additives into diesel fuel. Nano-alumina is added in three proportions into diesel, diesel–bioethanol, and diesel–biobutanol blends for further enhancement of performance. The novelty of this study is the utilization of the bio-alcohols manufactured from the waste vegetables and fruits which are reducing the land pollution, disposal cost, and the decrease in the dependency on diesel fuel. Blends of diesel–bioethanol and diesel–biobutanol are prepared and tested for homogeneity at a controlled temperature of 25°C. The blends after the homogeneity test are tested for the required properties and compared with the base of commercial Bharat Stage VI diesel. One blend from three base fuels—diesel, diesel–bioethanol, and diesel–biobutanol—is being chosen and further blended with three proportions of nano-alumina particles (50 mg/l, 75 mg/l, and 100 mg/l) and further tested for efficiencies in compression ignition engine. By the comparison of efficiencies, one blend with one proportion of nano-alumina is being compared for the parameters of the engine in five load conditions. The thermal energy release during the fueling is being analyzed by monitoring the heat release rate and the pressure of the engine during the testing. The results revealed that the addition of bioethanol and biobutanol improves the heat release rate by 5%–7% from the base diesel; the addition of 100 mg/l of nano-alumina increases the heat release by further 6.5%–9.5% in the blends of diesel, diesel–bioethanol, and diesel–biobutanol blends, respectively, operated in the range of 75%–85% of brake power of the maximum brake power of the test engine. The emissions of nitrogen oxides and smoke from the engine in these conditions are significantly low while comparing diesel. This study directs the utilization of the renewable fuels such as bioethanol and biobutanol up to 20%, which saves the same extent of diesel fuel that is an import resource.
Prabakaran, B., Yasin, Mohd Hafizil Mat
Computational Investigation of Advanced Compression Ignition with Wet Ethanol in an OP-2S04-19-01-00026/30/2025
Alcohol fuels have inherent properties that make them suitable candidates to replace conventional fossil fuels in internal combustion engines by reducing the formation of harmful emissions such as lifecycle carbon dioxide (CO2), nitrogen oxides (NOX), and particulate matter (PM). There is an increasing amount of work to use fuels such as ethanol or methanol in mixing-controlled compression ignition (MCCI) as a replacement for diesel fuel. However, employing these fuels in a strictly MCCI strategy results in an evaporative cooling penalty that lowers indicated fuel efficiency. This work proposes the use of an advanced compression ignition (ACI) strategy with a high autoignition resistant fuel, where a fraction of the fuel is premixed and autoignited in conjunction with a fraction of fuel that is burned in a mixing-controlled manner to achieve diesel-like efficiencies with significant emission reductions. A computational model for MCCI with diesel and wet ethanol in an opposed piston two-stroke (OP-2S) engine was validated against experimental data. Diesel and wet ethanol MCCI were then compared at a similar operating condition, where it was seen that wet ethanol provided a significant reduction in NOX emissions but resulted in a lower indicated efficiency. A triple injection strategy to enable ACI is then proposed by redesigning one of the injectors to enable compression stroke injections. The injector included angle, the injection split fractions, and injection timings of the triple injection strategy were varied to understand the impact of each on combustion performance and emissions. An optimal triple injection strategy based on simulation data was approximated and then simulated to compare to conventional diesel (i.e., MCCI with diesel) and MCCI with wet ethanol. ACI demonstrated a 3.5% point efficiency improvement over MCCI with wet ethanol, resulting in an efficiency that was the same as conventional diesel while still demonstrating nearly a 4 times reduction in NOX emissions.
O’Donnell, Patrick Christopher, Gainey, Brian, Bhatt, Ankur, Huo, Ming, Lawler, Benjamin
Evaluation of Jet Fuels on Thermal Efficiency, NO X Emissions, Particulate Matter, and Particle Size Distribution in a Heavy-Duty Compression Ignition Engine2025-01-02446/16/2025
Alternative fuels such as Fischer-Tropsch Synthesized Paraffinic Kerosene (FT-SPK) and Catalytic Hydrothermal Conversion Jet (CHCJ) are among the important sustainable aviation fuels (SAFs) for future transportation. However, these alternative fuels often vary in their characteristics, depending on their feedstock and fuel production processes. Therefore, a detailed analysis of these alternative fuels' combustion, emissions, and efficiency must be performed under controlled experiments to understand the impact of fuel properties and operating conditions. This study used a single-cylinder research engine (SCE) with a compression ratio of 17:1. Extensive operating conditions were performed to determine the effect of each fuel on the engine performance, which can be fundamentally understood by fuel properties (e.g., cetane number, heat of combustion, and density) in comparison with Jet-A fuel. The experimental setup includes high-speed data acquisition for combustion analysis and gaseous and solid emissions benches for nitrogen oxides (NOX). Results suggested that an engine control management (ECM) strategy can potentially optimize the performance of these alternative jet fuels by compensating for differences in their fuel properties. This study aims to provide insights for future work on exploring different SAF fuels that are more environmentally friendly while meeting the required performance.
Cung, Khanh, Miganakallu Narasimhamurthy, Niranjan, Khalek, Imad, Hansen, Greg
An Experimental Study on Aqueous Ammonia and Diesel Dual-Fuel Combustion with Ignition Improving Additives in a Compression Ignition Engine2025-01-02316/16/2025
Ammonia is a potential vector of renewably produced hydrogen for combustion systems and decarbonisation of transport. However, anhydrous ammonia has health risks and difficult to handle due to its volatility and toxicity. Therefore, a water-based solution of ammonium hydroxide (NH4OH) was proposed to investigate the potential use as a fuel in a compression-ignition engine. Ammonium hydroxide, also referred to as aqueous ammonia, is liquid phase under atmospheric conditions and, therefore, the storage of such a fuel does not require high pressure. Previous work has established that ammonium hydroxide solution could contribute to energy release during co-combustion with fossil diesel. However, the presence of water reduced combustion stability and limited the extent to which aqueous ammonia could displace diesel. In addition, the characteristics of co-combustion and pollutant emissions of burning such a fuel remain less understood. This study therefore explores the potential of using ignition improving additives for ammonium hydroxide and diesel dual-fuel co-combustion in a diesel engine. Two chemical additives, hydrogen peroxide and ammonium nitrate, were selected to blend with ammonium hydroxide at varied concentrations. The solution was aspirated into the engine via port injection into the preheated air intake, while diesel was supplied via direct injection at 500 bar. Tests were undertaken at constant engine indicated mean effective pressure (IMEP) but with varying levels of displacement of diesel fuel by aspirated aqueous ammonia. Measurements were made of combustion characteristics and both particulate and gaseous emissions in the exhaust. The addition of hydrogen peroxide reduced the duration of ignition delay relative to aqueous ammonia and diesel only co-combustion, especially at higher additive concentrations of 1% and greater. Furthermore, the presence of both ignition improvers saw an equivalent energy release from aqueous ammonia achieved with reduced injection duration and a higher proportional contribution to overall engine load. The aqueous ammonia and diesel dual-fuel co-combustion resulted in a general increase in both particulate mass and number. This trend was especially noticeable with 0.5% ammonium nitrate added to the fuel, where the number of particles was 122% greater than diesel only combustion and particle diameter mainly ranged between 10-50 nm. Meanwhile, despite an increase in fuel-bound nitrogen with the use of ammonia, exhaust emissions of nitrogen oxides did not linearly increase, and both ignition improvers reduced nitrogen oxides relative to ammonia and diesel co-combustion without additives.
Han, Yanlin, Hellier, Paul, Schonborn, Alessandro, Ladommatos, Nicos
Numerical Investigation into the Combustion and Emission Characteristics of Ammonia Direct Injection Mechanism2025-01-02416/16/2025
The effects of diesel and the ammonia ratio on the emissions and combustion characteristics of ammonia utilized in AMMONIA direct injection (AMMONIA-Di) engines were investigated through experimental and numerical investigations. A rapid compression expansion machine (RCEM) modified to facilitate the dual direct injection fuel (diesel-ammonia) - compression ignition (CI) method was used to conduct the experiment. A compression ratio (CR) of 19 and an ammonia energy percentage ranging from 10% to 90% were used in the experiment. Changes were made to the start of injection (SOI) from 0o to 40o before top dead center (BTDC) in order to find the best auto-ignition properties of ammonia. In order to facilitate auto-ignition, the diesel’s SOI was maintained at 10o BTDC. Computational fluid dynamics (CFD) modeling was used to establish the detailed emission propagation during the combustion process. During the expansion step, ammonia goes through a second stage of combustion, demonstrating that the fuel cannot burn entirely during the initial auto-ignition process. Emissions of CO2, HC, and NOx rise when direct injection CI engines use up to 50% ammonia. When SOI is applied to ammonia at 0 and 40 BTDC with an ammonia energy percentage higher than 50%, the emissions vary significantly, indicating poor combustion quality that encourages the production of emissions.
Setiawan, Ardhika, Lim, Ocktaeck
Analysis of Diesel-Ethanol Blends: Impact on Spray Behavior and Combustion Properties under Various Injection Parameters in CI Settings2025-01-02086/16/2025
With rising fuel consumption across road transportation, there is growing interest in expanding the market share of renewable fuels, such as ethanol. Ethanol can be produced from raw materials from various starch-rich plants. In CI engines, ethanol cannot be utilized on its own, largely due to its low cetane number. In this study, a constant volume combustion chamber (CVCC) is employed to investigate the effects of adding ethanol in diesel with different proportions (10%, 20%, 30% v/v) on the spray and combustion characteristics. Optical techniques, such as shadowgraph and direct photography using high-speed imaging methods, were employed to reveal the spray and flame development process. This study examines the effects of varying fuel injection pressures (50, 80, and 110 MPa) and ambient pressures (1.5 and 3 MPa) on diesel-ethanol (DE) fuel blends. The study emphasizes the impact of DE blending ratios on the spray’s macroscopic features, while the microscopic characteristics are investigated through computational fluid dynamics (CFD) simulations to provide a comprehensive analysis of spray behavior under these conditions. The spray experiments are further combined with the flame and combustion characteristics of the blended fuel under different temperatures (800, 1000K), oxygen concentrations (15, 21%), and ambient density (15 kg/m3). It is revealed that the increase in ethanol content in diesel alters the fuel's physicochemical properties, resulting in a reduction not only in kinematic viscosity but also surface tension, thereby modifying the spray's behavior. Consequently, the average SPL is reduced, while a broader SCA is observed. Additionally, the Sauter Mean Diameter decreases with an increased ethanol ratio in diesel which indicates an improved atomization process compared to pure diesel fuel. In the case of spray combustion characteristics and the flame development process, the results demonstrate that the ethanol-blended spray flame has an unstable flame boundary, displaying multiple wrinkles at the outermost flame edge. Moreover, as the ethanol proportion increases, the peak combustion pressure experiences a slight drop under most test conditions. However, higher ambient temperature and oxygen concentration could significantly reduce the ignition delay. A thorough discussion of the mechanism underlying these events will be provided.
Putra, I Komang Gede Tryas Agameru, Lim, Ocktaeck
Higher Content n-Butanol Blending Ratios in Diesel Fuel Spray and Combustion Characteristics: Addressing Oxygenated Fuel Challenges with Spark-Assisted Combustion Strategies2025-01-02106/16/2025
This study investigates the effects of oxygenated fuels, specifically long-chain alcohols, impact fuel atomization and combustion behavior in CI engines. The objective is to examine how higher n-butanol blending ratios in diesel fuel influence spray dynamics and combustion performance under varying engine conditions using an advanced combustion strategy. Experiments were conducted using a constant volume chamber (CVC) and a rapid compression-expansion machine (RCEM), both designed to replicate CI engine conditions. N-butanol was blended with diesel at ratios ranging from 70% to 90% with 10% increments, and key parameters such as spray formation, cone angle, penetration length, in-cylinder pressure, combustion performance, and efficiency were analyzed. The study also evaluated the effects of varying injection pressures on spray behavior. The results demonstrate that increasing n-butanol content significantly alters spray and combustion characteristics. Higher n-butanol proportions lead to longer spray tip penetration and larger spray areas at higher injection pressures, while the cone angle remains relatively unchanged. The 90% n-butanol blend exhibited the most distinct differences from pure diesel. However, due to n-butanol’s high latent heat of vaporization, in-cylinder temperatures decreased, resulting in longer ignition delays. To mitigate this, a spark-assisted compression ignition (SACI) strategy was employed, with adjustable spark duration to assess its impact. Compared to pure diesel, SACI-applied n-butanol/diesel blends exhibited higher peak in-cylinder pressure and heat release rates, improving indicated thermal efficiency. Additionally, ringing intensity (RI) assessments confirmed that all tested conditions remained below the 5 MW/m2 threshold, ensuring acceptable combustion stability. This study provides a comprehensive analysis of n-butanol/diesel blends under SACI conditions, demonstrating their potential to enhance spray and combustion characteristics. The findings underscore n-butanol’s promise as a sustainable alternative fuel, addressing key challenges in dual-fuel combustion strategies.
Warsita, I Wayan, Lim, Ocktaeck
Enabling Neat Alcohol Combustion in a Heavy-Duty Diesel Engine with Exhaust Rebreathing13-06-03-00225/23/2025
In this study, a strategy for MCCI combustion of a novel alcohol fuel is demonstrated. The novel fuel, “GrenOl”, is the result of the catalytic upgrade of sustainable ethanol into alcohols of higher molecular weight. The composition of GrenOl includes approximately 70% 1-butanol, 15% 1-hexanol, and 5% 1-octanol by mass, resulting in a cetane number around 18. In order to achieve mixing-controlled compression ignition with GrenOl, an exhaust rebreathing strategy is employed. In this strategy, the exhaust valve reopens for a part of the intake stroke, inducting hot exhaust into the cylinder and preheating the fresh air. This study investigates the feasibility of operating with such a valve strategy from idle to peak torque. At idle, the primary challenge is ensuring stable combustion by inducting adequate exhaust to achieve ignition. Under load, when cylinder temperatures are higher, the primary challenge is ensuring sufficient air is inducted to achieve the target torque. It was found that a modest exhaust rebreathing valve strategy could ensure stable combustion with diesel-like emissions and efficiency from idle to peak torque. Coefficient of variation of IMEP as low as 2% was achieved at idle, matching diesel idle stability despite the very low cetane number of the fuel. At medium load, indicated specific fuel consumption was as low as 235 g/kWh, and engine-out indicated specific NOx emissions were as low as 4 g/kWh. Peak torque was attained despite the volumetric efficiency penalty imposed by exhaust rebreathing. These results demonstrate the feasibility of operating a diesel engine on neat, sustainable, ethanol-derived fuel over the entire engine operating map with minimal well-defined design modifications. Future work should extend these findings to multicylinder engines and challenging cold start conditions.
Trzaska, Joseph, Xu, Zhihao, Boehman, André L.
Experimental Investigation of Carbon Nanotube Additives Effect on Performance and Emission of a High-Injection Pressure Common Rail Diesel Engine03-18-03-00205/16/2025
Due to the continuous decrease in fossil fuel resources, and drawbacks of some biofuel properties, in addition to restricted environmental concerns, it becomes a vital manner to innovate some approaches for energy saving and emission reduction. One of the promising approaches is to enhance the fuel properties via adding nanoparticles. Carbon nanotubes (CNTs) blended with biofuels get extensive investigations by researchers using conventional diesel engines at relatively limited operating regimes. The objective of this work is to extend these studies using diesel fuel, rather than biofuels, on a high-injection pressure (1400–1600 bar) common rail diesel engine at wide operating conditions and higher CNT concentrations. Experimental results show an increase in peak pressure up to 24.46% than pure diesel when using 100 ppm CNTs concentration. Also, BSFC has decreased by 33.19%, and BTE increased by 54.2% compared to pure diesel fuel at high speeds and loads. NOx and CO2 emissions raised by 24.3% and 23.3%, respectively, while CO emission decreased by 23.68%. These results could be a motivation for extra investigations for CNTs using smaller sizes, lower than 10 Nm, at wider engine regimes and particle concentrations.
Moaayet, Sayed, Neseem, Waleed Mohamed, Amin, Mohamed Ibrahim, Shahin, Motasem Abdelbaky
Improvement of Lean Burn Characteristics with Ozone Addition in a Diesel Micro-pilot Natural Gas Engine2024-32-01044/18/2025
Ozone (O3) was introduced into the intake air in a natural gas fueled engine ignited by micro-pilot of diesel fuel, to utilize the reactive O-radicals decomposed from the O3 for the promotion of the combustion and for improvements in the thermal efficiency and exhaust emissions. Experiments were carried out in a single cylinder engine to elucidate the effects of the ozone addition under the lean burn conditions. A supercharger was employed to increase the intake air amount and vary the equivalence ratio of natural gas. The experimental results showed that the O3 addition has a limited effect on the ignition of the diesel fuel injected near top dead center, while the heat release during the flame propagation in the natural gas/air mixture was increased at the lower equivalence ratio of natural gas. Further the ignition of natural gas was promoted, resulting in the increase of the combustion efficiency and the degree of constant volume heat release. The cooling loss and the NOx emissions decreased due to the leaner burn achieved by the supercharging. Overall, the indicated thermal efficiency and the exhaust emissions can be improved by the supercharging combined with the O3 addition.
Kobashi, Yoshimitsu, Miyata, Shoki, Kawahara, Nobuyuki, Inagaki, Ryuya
Characterization of Thermo-Catalytically Reformed Diesel Injection and Ignition in Comparison to Conventional Diesel Fuels2024-32-00574/18/2025
It is widely known that with decreasing oil reserves on a global scale there is a need for alternative energy sources. Therefore, the introduction of various alternative fuels is of utmost importance. One way of producing alternative fuels is the Thermo-catalytic Reforming (TCR) process which was developed by the Fraunhofer-Institute for Environmental, Safety and Energy Technology (UMSICHT). For an application in conventional diesel engines, however, it is important to investigate the spray behavior of such TCR Diesel fuels in comparison to conventional Diesel fuels under engine-like operating conditions. Two different batches of TCR Diesel were compared with conventional Diesel fuels. The results show batch-dependent significant differences in the penetration length of liquid and vapor as well as in the spray area, which gives clear indications of altered mixture formation quality. Furthermore, ignition timing and ignition location were evaluated for reactive conditions using OH* chemiluminescence. The results also show clear differences to conventional fuels depending on the production batch. Overall, the differences found are so clear that a development towards less variation in the fuel properties seems sensible. The analytical methods used are suitable for investigating fuel differences before use in the engine.
Seeger, Jan, Taschek, Marco, Apfelbacher, Andreas, Strauß, Lukas, Rieß, Sebastian, Wensing, Michael
An Experimentation of Performance of Compression Ignition Engine Fueled with Nano-alumina–Enhanced Diesel, Diesel–Ethanol, and Diesel–Butanol Blends2025-01-50254/3/2025
This study is to use the renewable fuels such as bioethanol and biobutanol as performance improving additives into diesel fuel. Nano-alumina is added in three proportions into diesel, diesel–bioethanol, and diesel–biobutanol blends for further enhancement of performance. The novelty of this study is the utilization of the bio-alcohols manufactured from the waste vegetables and fruits, which are reducing the land pollution, disposal cost, and the decrease in the dependency of diesel fuel. Blends of diesel–bioethanol and diesel–biobutanol are prepared and tested for the homogeneity in the controlled temperature of 25°C. The blends after the homogeneity test are tested for the required properties and compared with the base of commercial Bharat Stage VI diesel. One blend from three base fuels such as diesel, diesel–bioethanol, and diesel–biobutanol is being chosen and further blended with three proportions of nano-alumina particles (50 mg/L, 75 mg/L, and 100 mg/L) and further tested for efficiencies in compression ignition engine. By the comparison of efficiencies, one blend with one proportion of nano-alumina is being compared for the parameters of the engine in five load conditions. The thermal energy release during the fueling is being analyzed by monitoring the heat release rate and the pressure of the engine during the testing. The results revealed that the addition of bioethanol and biobutanol improves the heat release rate by 5%–7% from the base diesel; the addition of 100 mg/L of nano-alumina increases the heat release by further 6.5%–9.5% in the blends of diesel, diesel–bioethanol, and diesel–biobutanol blends, respectively, operated in the range of 75%–85% of brake power of the maximum brake power of the test engine. The emissions of nitrogen oxides and smoke from the engine in these conditions are significantly low while comparing diesel. This study directs the utilization of the renewable fuels’ such as bioethanol and biobutanol up to 20%, which saves the same extent of diesel fuel—an import resource.
Prabakaran, B., Yasin, Mohd Hafizil Mat
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