Browse Topic: Cetane

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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
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
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
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
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
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
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
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
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
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
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
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.
Comprehensive Investigation of Combustion Characteristics, Emissions, and Tribological Properties of Synthetic Kerosene (S8) in a CVCC and CRDI Research Engine2025-01-84434/1/2025
There is a need to reduce both the greenhouse gas emissions of internal combustion engines, and the reliance on traditional fossil fuels like Ultra Low Sulfur Diesel (ULSD). In this research, a synthetic paraffinic kerosene fuel, designated S8 and created from natural gas feedstocks using the Fischer-Tropsch process was investigated to determine its autoignition and combustion characteristics, emissions, and tribological properties. This fuel, S8, was found to have a Derived Cetane Number (DCN) of 62, which reflects a shorter Ignition Delay (ID), and Combustion Delay (CD) compared to ULSD, which has a DCN of 48. However, due to the chemical properties of S8, it lacks sufficient lubrication qualities in comparison to ULSD, so addition of 3% methyl oleate by mass was used to improve lubricity. The shorter ignition delay of S8, initially observed in a Constant Volume Combustion Chamber (CVCC) and confirmed in a fired Common Rail Direct Injection (CRDI) experimental engine. Investigations with Mie scattering He-Ne laser instrument, revealed the superior atomization of S8, which resulted in a Sauter Mean Diameter (SMD) of 19.2 μm, 8% smaller than that of ULSD. The combined effect of the superior atomization and shorter ID of S8 resulted in a reduction of the premixed combustion event for S8, with smoother engine operation due to the greater proportion of mixing-controlled combustion. This characteristic was also reflected in the comparison of the Low Temperature Heat Release (LTHR) region of S8 with that of ULSD. In LTHR, S8 released more energy during the low temperature cool flame formation region and entered High Temperature Heat Release (HTHR) sooner than ULSD. Analysis of the emissions of the CRDI engine when operated with S8 was conducted with the engine under a sustained load at 5.4 bar Indicated Mean Effective Pressure (IMEP), and the results were compared with identical operating parameters using ULSD. A 14% reduction in NOx emissions and a 33% reduction in soot was achieved compared to ULSD.
Soloiu, Valentin, Willis, James, Norton, Coleman, Davis, Zachary, Graham, Tristan, Nobis, Austin
A Study on Cetane on Demand Technology Part 1 - Development of Fuel Reformer to Improve Fuel Ignitability2025-01-84474/1/2025
The integration of low-octane gasoline with a compression ignition combustion system has been proposed as a strategy to reduce Well-to-Wheel CO2 emissions from automobiles using petroleum-based fuel. In the current situation where low-octane gasoline is not widely available in the market, onboard reforming of commercial gasoline to increase the cetane number (lower the octane number) allows for compression ignition combustion even with commercial gasoline. This requires “Cetane on Demand” technology, which enables compression ignition combustion with both commercial gasoline and low-octane gasoline. It is known that the ignition property of fuel is enhanced when the fuel is oxidized to generate hydroperoxides. Moreover, the use of N-hydroxyphthalimide (NHPI) as a catalyst promotes hydroperoxide generation at low temperatures. The objective of this study is to develop a device that enhances the ignition properties of gasoline through onboard fuel reforming. Initially, from the seven kinds of NHPI-supported solid catalysts, a catalyst appropriate for a flow reactor operating at ambient pressure was selected. The NHPI-supported ZSM-5 catalyst demonstrated the highest performance in hydroperoxide formation under flow reactor conditions. Subsequently, with a focus on onboard reforming, two types of reactors (spiral-type reactor and inner-circulation type reactor) and two methods of air introduction (metal mesh bubbler and mechanical stirring bubbler) to ensure adequate contact between the fuel, air, and solid catalyst were designed and prototyped. The combination of the spiral-type reactor and mechanical stirring air introduction exhibited the best performance in hydroperoxide formation.
Hashimoto, Kohtaro, Yamada, Yoshikazu, Matsuura, Katsuya, Kudo, Tomohide, Chishima, Hiroshi, Al-Taher, Maryam, Kalamaras, Christos, Albashrawi, Reem
A Study on Cetane on Demand Technology Part 2: Gasoline Reforming and Ignitability Evaluation2025-01-84444/1/2025
The integration of low-octane gasoline with a compression ignition combustion system has been proposed as a strategy to reduce Well-to-Wheel CO2 emissions from automobiles in petroleum-based fuel. However low-octane gasoline is not widely available in the market currently. Onboard reforming of commercial gasoline to increase the cetane number (lower the octane number) allows for compression ignition combustion even with commercial gasoline. To reform commercial gasoline, a reformer with a spiral structure reactor and mechanical stirring air introduction was designed and prototyped based on the results of toluene reforming tests (A Study on Cetane on Demand Technology Part 1: Development of fuel reformer to improve fuel ignitability). Using N-hydroxyphthalimide (NHPI)-supported ZSM-5 as a catalyst, commercial gasoline was reformed. As a result, 25.5 liters of reformed gasoline was obtained. The hydroperoxide concentration in the entirety of our reformulated gasoline was determined to be 1.5 mmol/L, based on the hydroperoxide concentration measured at each sampling site and the corresponding volume collected. The ignitability of the reformed gasoline was evaluated using an internal combustion engine. Under premixed homogeneous conditions, no difference in ignitability was observed between the gasoline before reforming and the reformed gasoline. However, under non-uniform/diffusion combustion conditions, it was confirmed that the ignitability of the reformed gasoline improved compared to the gasoline before reforming. For the factor analysis, a chemical reaction calculation was conducted, and it was found to be due to the concentration of OH derived from the reformed gasoline. Under diffusion combustion (diesel-like) conditions, the evaluation of engine combustion showed that reformed gasoline expands the lean limit and improves combustion stability in the low-load operating range.
Matsuura, Katsuya, Hashimoto, Kohtaro, Yamada, Yoshikazu, Al-Taher, Maryam, Kalamaras, Christos, Voice, Alexander, Bhadra, Kaustav
Control-Oriented Statistical Model of In-Cylinder Pressure, Combustion Phasing, and Torque for Compression-Ignition Engines Operating with Low Cetane Fuels2025-01-83514/1/2025
Sustainable aviation fuels are becoming more widely available for current and future engine powered propulsion systems. However, the diversity of ignition behavior in these fuels poses a challenge to achieving robust, efficient operation. Specifically, low cetane fuels with poor ignitability exhibit highly variable torque production unless fuel is injected earlier during compression. The tradeoff is that earlier injection may cause dangerously high in-cylinder pressure rise rates. Novel models that can simulate these competing behaviors are needed so that appropriate strategies may be developed for controlling combustion at low cetane fueling conditions. This work builds upon a previously developed model that simulates asymmetric combustion phasing (CA50) distributions as a function of fuel cetane, fuel injection timing, and electrical power supplied to an in-cylinder thermal ignition assist device. An extension of the model is presented in which the phasing output is used to reconstruct in-cylinder pressure traces, by which indicated mean effective pressure (IMEP) can then be simulated. Additionally, a functional form is parametrized for modeling maximum in-cylinder pressure rise rate (MPRR). The model’s parameters are regressed using a total 121,237 engine cycles of experimental data from a commercial CI engine operating with four fuel blends with cetane number ranging from 25 to 48. Relative to the data, the model simulates mean CA50 within a root mean square error (RMSE) of approximately 3 CAD over a range of 64 CAD, mean IMEP within an RMSE of 0.85 bar over a range of 5.8 bar, and mean MPRR within an RMSE of 6.1 bar/CAD over a range of 88 bar/CAD. Along with the mean-value trends, it accurately emulates the variability of all three combustion metrics. Ultimately, this work marks the first time a low-order, control-oriented model simulates statistical distributions of CA50, IMEP, and MPRR.
Ahmed, Omar, Middleton, Robert, Stefanopoulou, Anna, Kim, Kenneth, Kweon, Chol-Bum
Impacts of Injection Pressure on Split-Injection Energy-Assisted Compression-Ignition Combustion of Low Cetane Number SAFs with a Gaussian-Shaped Ribbed Piston Bowl Design2025-01-83504/1/2025
The impact of injection pressure on a split-injection energy-assisted compression-ignition (EACI) combustion strategy was studied in an optically accessible engine with a custom ribbed piston bowl design. Three injection pressures (600, 800, and 1000 bar) were investigated for three split-injection dwells (1.5, 2.0, and 2.5 ms) with a fixed second injection timing of -5.0 CAD. The Gaussian-shaped ribbed piston bowl design was employed to position hot combustion gases from the first injection near the centrally located injector to enable rapid ignition and mixing-controlled combustion of the second injection. At 600-bar injection pressure, as injection dwell was shortened, relocation of hot combustion gases near the injector became increasingly more difficult due to less available time for relocation and due to the higher in-cylinder densities at the start-of-injection (SOI) for the first injection. Increased injection pressure (800 and 1000 bar) improved the relocation of the first injection combusted gases and increased the number of fuel jets rapidly igniting and undergoing mixing-controlled combustion during the second injection. Injection pressures of 800 and 1000 bar for a 2.0-ms injection dwell resulted in a greater number of fuel jets rapidly igniting than for the 600-bar injection pressure with a 2.5-ms injection dwell. These results suggest there is potential to achieve EACI operation at more application-relevant engine speeds through the utilization of custom piston bowl designs which allow for stable engine operation with higher injection pressures.
Amezcua, Eri, Stafford, Jacob, Kim, Kenneth, Kweon, Chol-Bum, Rothamer, David
Combustion and Emission Performance from the Use of Acid-Catalysed Butanol Alcoholysis Derived Advanced Biofuel Blends in a Compression Ignition Engine2025-01-84454/1/2025
Low-carbon alternatives to diesel are needed to reduce the carbon intensity of the transport, agriculture, and off-grid power generation sectors, where compression ignition (CI) engines are commonly used. Acid-catalysed alcoholysis produces a potentially tailorable low-carbon advanced biofuel blend comprised of mixtures of an alkyl levulinate, a dialkyl ether, and the starting alcohol. In this study, model mixtures based on products expected from the use of n-butanol (butyl-based blends) as a starting alcohol, were blended with diesel and tested in a Yanmar L100V single-cylinder CI engine. Blends were formulated to meet the flash point, density, and kinematic viscosity limits of fuel standards for diesel, the 2022 version of BS 2869 (off-road). No changes to the engine set-up were made, hence testing the biofuel blends for their potential as “drop-in” fuels. Changes in engine performance and emissions were determined for a range of diesel/biofuel blends and compared to a pure diesel baseline. The ratio of butyl-based biofuel components ranged between 65 – 90 vol% n-butyl levulinate, 5 – 30 vol% di-n-butyl ether, and 5 – 10 vol% n-butanol. Formulating the blends to match physical property limits ensured that engine operation was not significantly influenced by changes in these selected properties. Emissions of CO, NOX, total hydrocarbons (THC), and PM2.5 and particle number (PN) size distributions were measured. Compared to the baseline diesel, ignition delays were longer. The brake-specific fuel consumption of some butyl-based blends at high loads was within 5% of the diesel baseline. Most blends caused a less than 3% reduction in peak in-cylinder pressure at high loads, which contributed to maintaining engine efficiency. PM2.5 and PN emissions were reduced significantly. CO and THC specific emissions increased relative to diesel for all blends, potentially due to their reduced derived cetane number. This however, resulted in increased premixed combustion favouring reductions in particulate emissions. The competing effects of changes in adiabatic flame temperatures and charge cooling effects, contributed to maintaining blend NOX emissions close to those of diesel. The results demonstrated the biofuel blends may have the potential to be low-carbon fuels used CI engines.
Wiseman, Scott, Li, Hu, Tomlin, Alison S.
Diesel Engine Performance and Combustion Imaging Analysis of Gas-to-Liquid and Polyoxymethylene Dimethyl Ether Blended Fuels04-18-02-00102/12/2025
To reduce carbon dioxide emissions from automobiles, the introduction of electric vehicles to the market is important; however, it is challenging to replace all existing IC engine vehicles with electric ones. Consequently, there is increasing anticipation for the use of carbon-neutral fuels, such as e-fuels. This study investigates the effects of GTL (gas-to-liquid), as a substitute for e-fuel, produced from natural gas via the Fischer–Tropsch synthesis method and polyoxymethylene dimethyl ether (OMEmix) produced from methanol, on engine performance. Additionally, combustion image analysis was conducted using a rapid compression and expansion machine (RCEM). GTL fuel combusts similarly to conventional diesel fuel but has slightly lower smoke emissions because it does not contain aromatic hydrocarbons. Further, its high cetane number results in better ignition properties. During the combustion, unburnt hydrocarbons and smoke are generated in the spray flame interference region near the cylinder wall due to insufficient oxygen, and as it moves from the cylinder wall toward the center of the cylinder, the re-oxidation is observed, which is reflected in the heat release rate as the after-burning duration. When the OMEmix is mixed with hydrocarbon fuels such as GTL, combustion continues even in the spray flame interference region, leading to a reduction in the after-burning duration and significantly lower smoke emissions. Further, the GTL was divided into four distillation regions, that are GTL Light, GTL Light Middle, GTL Middle Heavy, and GTL Heavy, and the effects of low and high-boiling fractions in GTL on diesel combustion were investigated. Heavy fractions have excellent ignition properties, resulting in shorter lift-off (set-off) length during combustion. However, due to the poor evaporation characteristics, they have longer high-temperature residence time, leading to greater cooling losses and reduced thermal efficiency. On the other hand, light fractions have longer lift-off lengths, mix well with air before combustion, and have shorter combustion durations compared to heavy fractions. Finally, an engine performance was evaluated using a fuel mixture of the fuel with the heavy fractions removed from GTL (heavy-cut GTL) and OMEmix in a 1:1 ratio.
Shibata, Gen, Yuan, Haoyu, Yamamoto, Hiroya, Tanaka, Shusuke, Ogawa, Hideyuki
Experimental Study on Combustion and Emission Characteristics of a Two-Stroke Engine applying PODE/Methanol Blends Direct Injection2025-01-71121/31/2025
In order to realize the Paris Agreement, which aims to strengthen the global response to climate change, conventional internal combustion engines (ICE) need to contribute to reducing carbon emissions and improving thermal efficiency. More importantly, in the face of energy shortages, it is urgent to search for sustainable fuels. Poly-oxymethylene dimethyl ethers (PODE) and methanol are both regard as important low-carbon, alternative fuels due to their high oxygen content. Using PODE can overcome the characteristics of methanol as a low-reactivity fuel with a low cetane number and poor ignition properties. In this study, the combustion and emission characteristics of PODE/methanol blends were investigated in a two-stroke direct injection engine. Firstly, the performance of the engine under pure PODE (P100) and PODE/methanol blends (P50) was compared. The results show that at BMEP of 0.31 MPa and injection timing of -8°CA ATDE, P50 blends have lower CO2, CO, NOX and THC emissions than P100 fuel. However, the start of combustion of P50 is delayed slightly and ITE is lower than that of P100. Then, the effect of injection timing on the performance of the P50 engine was investigated. With the delay of fuel injection timing, NOX emissions decrease, but CO2, CO, and THC emissions increase. Moreover, as the injection timing is delayed, the engine COVIMEP was reduced and combustion stability was improved. The engine indicated mean effective pressure (IMEP) reaches its maximum value of 0.441MPa at -8°CA ATDC and decreases as injection timing is delayed. However, the indicated thermal efficiency (ITE) decreases with the delay of injection timing, reaching a maximum of 41.8% at -8°CA ATDC. This study provides a theoretical foundation for adopting PODE/methanol blends in diesel engines, highlighting their potential to reduce conventional emissions while maintaining operational feasibility. Further research on varying methanol ratios and load conditions is recommended.
Dong, Pengbo, Sun, Zhuohan, Wang, Qingyang, Wang, Yang, Cui, Jingchen, Zhang, Zhenxian, Long, Wuqiang
Physicochemical Characterization and Potential Applications of Biodiesel Produced from Industrial Fish Waste2024-01-510611/22/2024
Biofuels are gaining significant global attention as renewable and alternative energy sources, produced from various materials through different extraction methods and conversion processes. Food industry generates not only substantial organic waste, presenting economic and ecological challenges but also potential opportunities for valorization. This study focuses on recovering industrial fish waste from the manufacture of canned tuna, specifically targeting non-food and abundant fish co-products such as heads, bones, skin, and viscera, which constitute nearly 50% of the fish body. The process involves several steps: oil extraction using Soxhlet extraction, purification, and conversion into biodiesel via transesterification, followed by physicochemical analysis. The experiments revealed that 32.41% of fish waste was in the liquid phase (a mixture of hexane and oil), and the extracted oil accounted for 26.56% of the total fish waste weight (from 1.012 kg of waste, approximately 268.78 g of oil was extracted, equivalent to 280.36 mL). The fatty acid composition influenced the cetane number of the biodiesel. Two types of biodiesel (methyl and ethyl esters) were produced from the extracted fish oil through transesterification with methanol or ethanol and sulfuric acid (H2SO4). The analysis showed that the produced biodiesels possess properties similar to conventional diesel, indicating their suitability for use in diesel engines. This research highlights the potential of fish waste valorization to reduce fossil fuel consumption and promote sustainable energy solutions.
Bousbaa, Hamza, NAIMA, Khatir, Lamia, Medjahed, Benramdane, Mohammed, Balasubramanian, Dhinesh, Johnson, Anish Jafrin Thilak
Fuel Quality Assessment of Green Diesel Produced from Waste Cooking Oil2024-01-429311/5/2024
Waste cooking oil can be converted into fuel for internal combustion (IC) engine applications by transesterification or pyrolysis. Transesterification results in the production of fatty acid methyl esters called biodiesel. The variability in biodiesel composition and properties from diesel fuel leads to engine re-calibration that requires significant time and effort. Diesel-like hydrocarbons can be produced by catalytic pyrolysis of used cooking oil. Such fuel can be used as a drop-in fuel in IC engine applications. Hydrogen at high pressures and a catalyst generally promote deoxygenation during pyrolysis. Recently, novel heterogenous acid catalysts such as Ni-impregnated activated carbon (AC) and Ag-Co-impregnated AC catalysts were developed to produce deoxygenated fuel by pyrolysis at atmospheric pressure without using hydrogen. Homogenous base catalysts such as sodium hydroxide can also be used in pyrolysis to produce diesel-like fuel. The present work compares the suitability of pyrolysis oils produced from waste cooking oil using these catalysts with those produced without a catalyst. The reaction temperature was optimized for the yield and quality of the fuel. The composition of the diesel-like fuel thus produced is measured using GC-MS. Physicochemical properties such as cetane index, viscosity, density, flash point, and caloric value were measured following the ASTM standard test procedure. The results show that the reaction temperature significantly influences the kinematic viscosity of the pyrolysis oil. It is found that compared to the pyrolysis oil produced without a catalyst, the oil produced using acid catalysts had a higher calorific value. The increase in calorific value is because of the deoxygenation reactions promoted by the catalysts. The pyrolysis oils had physicochemical properties in the range of petroleum diesel. The present study shows that pyrolysis of used cooking oil without hydrogen using acid and base catalysts can produce high-quality diesel-like fuel for IC engine applications.
Chellachamy, Adhikesavan, Krishnasamy, Anand
Effects of Fuel Distillation Characteristics on the Performance of Catalyst-Heating Operation in a Medium-Duty Off-Road Diesel Engine2024-01-427811/5/2024
Catalyst heating operation in compression-ignition engines is critical to ensure rapid light-off of exhaust catalysts during cold-start. This is typically achieved by using late post injections for increased exhaust enthalpy, which retardability is constrained by acceptable CO and unburned hydrocarbons emissions, since they are directly emitted through the tailpipe due to the inactivity of the oxidation catalyst at these conditions. Post-injection retardability has shown to be affected by the cetane number of the fuel, but it is unclear how other fuel properties affect the ability to retard the combustion. This study aims to understand the impact of the distillation characteristics of the fuel on the performance of catalyst heating operation and on post-injection retardability. In this study, experiments are performed in a single-cylinder medium-duty diesel engine fueled with three full boiling-range diesel fuels with different distillation curves using a five-injection strategy (two pilot, one main, two post) optimized for catalyst heating operation. The two post-injections are block-shifted to more retarded timings for three different first-post to second-post fuel split ratios and at a constant engine load. Decreasing the volatility of the fuel leads to higher exhaust enthalpy values and lower CO and unburned hydrocarbon emissions. The increase in exhaust enthalpy is caused by an additional fuel requirement to compensate for higher heat losses caused by higher flame-wall interactions with the less volatile fuels. The decrease in CO and unburned hydrocarbon emissions is caused by lower formation of overly-lean regions that do not burn properly using with the less volatile fuels. Thus, low volatility fuels improve the retardability of post injections. Chemical kinetic simulations are performed to better understand autoignition reactivity differences between fuels, concluding that fuel effects are more important for the pilot injections due to the low in-cylinder temperature and high in-cylinder pressure at the time of injection.
Lee, Sanguk, Lopez Pintor, Dario, Cho, Seokwon, Busch, Stephen
Effects of Fuels Properties on Combustion and Emissions Characteristics of Light Duty GCI Engine2024-01-427911/5/2024
Our research group developed Gasoline Compression Ignition (GCI) fuel matrix based on the fuel properties, specifications and fuel sources in an effort to standardize the GCI fuel. This study attempts to experimentally validate the standardized GCI fuels to comply with the operational regimes of GCI engine. Two of the formulated GCI fuels (GCI7 and GCI8) with varying physical and chemical properties, and composition were investigated in a single cylinder compression ignition (CI) engine. In addition to fuel effects, the engine variables were parametrically varied at low (3 bar IMEP) and medium (7 bar IMEP) load conditions. At low loads, the fuel chemical effects played a crucial role in governing the combustion while physical effect had a negligible impact. Due to lower cetane number of GCI8 fuel, combustion is predominantly premixed for GCI8 fuel but GCI7 fuel shows a more pronounced diffusion combustion phase. The low temperature heat release (LTHR) is evident only for GCI8 fuel due to higher octane rating (RON = 60) whereas GCI7 fuel (diesel like) showed negligible LTHR phase. Despite improvements in engine operating parameters, the combustion performance of GCI8 is lower than GCI7 fuel. However, after improving the fuel injection strategies, GCI8 fuel showed improved peak in-cylinder pressure and heat release compared to GCI7 fuel. Double injection advanced the combustion phasing, shortened the ignition delay, and improved the burn rate when compared to single injection. Fuel composition played a crucial role in emission formation in that smoke emission is increased for GCI7 due to higher fraction of aromatics in the fuel compared to GCI8. The increased premixed effect due to lower cetane number of GCI8 decreased the fuel to air equivalence ratio and in-cylinder temperature in that NOX emission is reduced.
Qahtani, Yasser Al, Raman, Vallinayagam, Viollet, Yoann, Alhajhouje, Abdullah, Cenker, Emre, AlRamadan, Abdullah
Operation of a Compression-Ignition Kerosene Aviation Engine with Sustainable Aviation Fuel: An Experimental Study2024-01-600510/28/2024
The aviation industry is undergoing environmental scrutiny due to its significant greenhouse gas emissions. Sustainable aviation fuels (SAFs) are a vital solution for reducing carbon emissions and pollutants, aligning with global efforts for carbon-neutral aviation growth. SAFs can be produced via multiple production routes from different feedstock, resulting in significantly different physical and chemical fuel properties. Their suitability in a compression-ignition (CI) aircraft engine was evaluated through test bench investigations at TU Wien - Institute of Powertrain and Automotive Technology in partnership with Austro Engine. ASTM D7566-certified fuels like Hydrotreated Vegetable Oil (HVO), Fischer–Tropsch–Kerosene (FTK) or Alcohol to Jet (AtJ), but also an oxygen containing biodiesel have been tested extensively. Gaseous emissions, soot emissions, indication measurement data, efficiencies, and the like were acquired and comprehensively analyzed for engine operation with different fuels and fuel blends. Operation with all investigated fuels could be demonstrated successfully at three representative operating points with the original engine setup. At constant boundary conditions, neither maximum permitted in-cylinder pressure, pressure gradient, or exhaust gas temperature were exceeded (nevertheless, an adaption of the injection strategy is recommended). Ignition delay and combustion duration—dependent on fuel properties—greatly influence the formation of incomplete combustion products like HC and CO as well as NOx and soot emissions. Especially the extremely low cetane number of AtJ leads to a substantial increase in premixed combustion, which significantly influences NOx and soot emissions, depending on operating conditions. A low aromatic content (as found in HVO) is beneficial for reducing HC, CO, and soot due to the absence of ring-like molecule structures. Also, a reduced adiabatic flame temperature contributes to a decreased NOx concentration. The high oxygen content of the biodiesel is known to be beneficial for reducing HC, CO, and soot, while it contributes to increased NOx emissions. At comparable air/fuel ratios within a specific operating point, all tested fuels and fuel blends exhibit comparable CO2 emissions.
Kleissner, Florian, Hofmann, Peter
Numerical Investigations on Reducing Unburned Hydrocarbon and Carbon Monoxide Emissions in Reactivity-Controlled Compression Ignition Using Partial Reactivity Stratification with Alternative Fuels and Additive03-18-01-000510/4/2024
A numerical investigation has been performed in the current work on reactivity-controlled compression ignition (RCCI), a low-temperature combustion (LTC) strategy that is beneficial for achieving lower oxides of nitrogen (NOx) and soot emission. A light-duty diesel engine was modified to run in RCCI mode. Experimental data were acquired using diesel as HRF (high-reactivity fuel) and gasoline as LRF (low reactivity fuel) to check the accuracy and fidelity of predicted results. Blends of ethanol and gasoline with DTBP (di-tert-butyl peroxide) addition in a small fraction on an energy basis were used in numerical simulations to promote ignitability and reactivity enhancement of PFI charge. Achieving stable, smooth, and gradual combustion in RCCI is challenging at low loads, especially in light-duty engines, due to misfiring and poor combustion stability. DTBP is known for enhancing cetane number and accelerating combustion, and it is mixed in a PFI blend to avoid combustion deterioration. The factors governing reactivity stratification to achieve optimal combustion phasing were investigated in the present study. DTBP decomposition and its low-temperature oxidation chemistry were found to be responsible for affecting combustion phasing, heat release patterns, and emission trends. DTBP additive and different in-cylinder strategies were applied and studied to reduce unburned emissions. Adopting a multiple injection approach utilizing dual-pulse assisted in reducing HC and CO levels. It enhances combustion quality by providing adequate control over combustion phasing. Altering operating parameters like intake temperatures reduced HC, CO, and soot emissions by 97.6%, 57.6%, and 52.8%, respectively, compared to baseline gasoline/diesel RCCI data. Optimizing the injection timings of the first and second pulse helps achieve optimal combustion phasing and a 72.95% reduction in NOx emissions. The higher injection pressure of DI helped lower the CO and soot emissions by 53.33% and 51.84%, respectively.
Tripathi, Saurabh, Krishnasamy, Anand
Experimental Study of Lignin Fuels for CI Engines2024-37-00226/12/2024
This study explores the feasibility of using a sustainable lignin-based fuel, consisting of 44 % lignin, 50 % ethanol, and 6 % water, in conventional compression ignition (CI) marine engines. Through experimental evaluations on a modified small-bore CI engine, we identified the primary challenges associated with lignin-based fuel, including engine startup and shutdown issues due to solvent evaporation and lignin solidification inside the fuel system, and deposit formation on cylinder walls leading to piston ring seizure. To address these issues, we developed a fuel switching system transitioning from lignin-based fuel to cleaning fuel with 85 vol% of acetone, 10 vol% of water and 5 vol% of ignition improving additive, effectively preventing system clogs. Additionally, optimizing injection parameters, adopting a constant pressure delivery valve, and fine-tuning injection timing mitigated lignin deposit formation related to incomplete combustion or spray tip penetration to the cylinder wall. The successful combustion of the lignin-based fuel in the small-bored CI engine was confirmed in a wide range of chamber temperatures. The ignition delay was measured and analyzed using Arrhenius equation. The ignition quality of the lignin fuel was comparable with 1-pentanol with a cetane number of 18.2, which is acceptable for 2-stroke marine engines. Although further investigation is needed to assess long-term reliability, our findings underscore the potential of lignin-based fuel as a viable alternative fuel for marine engines.
Terauchi, Motoki, Simonsen, Tor, Mortensen, Simon, Schramm, Jesper, Ivarsson, Anders
Spectroscopy-Based Machine Learning Approach to Predict Engine Fuel Properties of Biodiesel03-17-07-00514/11/2024
Various feedstocks can be employed for biodiesel production, leading to considerable variation in composition and engine fuel characteristics. Using biodiesels originating from diverse feedstocks introduces notable variations in engine characteristics. Therefore, it is imperative to scrutinize the composition and properties of biodiesel before deployment in engines, a task facilitated by predictive models. Additionally, the international commercialization of biodiesel fuel is contingent upon stringent regulations. The traditional experimental measurement of biodiesel properties is laborious and expensive, necessitating skilled personnel. Predictive models offer an alternative approach by estimating biodiesel properties without depending on experimental measurements. This research is centered on building models that correlate mid-infrared spectra of biodiesel and critical fuel properties, encompassing kinematic viscosity, cetane number, and calorific value. The novelty of this investigation lies in exploring the suitability of support vector machine (SVM) regression, a burgeoning machine learning algorithm, for developing these models. Hyperparameter optimization for the SVM models was conducted using the grid search method, Bayesian optimization, and gray wolf optimization algorithms. The resultant SVM models exhibited a noteworthy reduction in mean absolute percentage error (MAPE) for the prediction of biodiesel viscosity (3.1%), cetane number (3%), and calorific value (2.1%). SVM regression, thus, emerges as a proficient machine learning algorithm capable of establishing correlations between the mid-infrared spectra of biodiesel and its properties, facilitating the reliable prediction of biodiesel characteristics.
Bukkarapu, Kiran Raj, Krishnasamy, Anand
Optical Diagnostic Study on Ammonia-Diesel and Ammonia-PODE Dual Fuel Engines2024-01-23624/9/2024
Ammonia shows promise as an alternative fuel for internal combustion engines (ICEs) in reducing CO2 emissions due to its carbon-free nature and well-established infrastructure. However, certain drawbacks, such as the high ignition energy, the narrow flammability range, and the extremely low laminar flame speed, limit its widespread application. The dual fuel (DF) mode is an appealing approach to enhance ammonia combustion. The combustion characteristics of ammonia-diesel dual fuel mode and ammonia-PODE3 dual fuel mode were experimentally studied using a full-view optical engine and the high-speed photography method. The ammonia energy ratio (ERa) was varied from 40% to 60%, and the main injection energy ratio (ERInj1) and the main injection time (SOI1) were also varied in ammonia-PODE3 mode. The findings demonstrate that ammonia-PODE3 mode exhibits better ignition characteristics than ammonia-diesel mode, resulting in an earlier ignition start, a larger flame area, a larger flame expansion speed, a shorter ignition delay time (IDT) and a shorter combustion duration (CD) due to the higher cetane number (CN) and a greater injection mass of PODE3 at the same energy input. Ammonia-PODE3 mode achieves larger maximum cylinder pressure (Pmax) and peak heat release rate (HRR) compared to ammonia-diesel mode. Furthermore, almost no soot was observed in ammonia-PODE3 mode throughout the entire combustion process. The results also indicate the start of the ignition is delayed and the first peak flame expansion speed decreases at a higher ammonia energy ratio. The maximum flame area is the largest at ERa = 60%, but the peak cylinder pressure and IMEP reach their highest values at ERa = 50%. Both the first peak flame area and the first peak flame expansion speed increase with the increase of ERInj1, and the Pmax and first peak HRR also increase. The IDT slightly extends with the increase of ERInj1, while CA50 advances and CD reduces. The start of the ignition is delayed with the advancement of the main injection time, and the largest flame area is observed at SOI1 = -12.5 °CA. Both the first Pmax and the maximum IMEP occur at SOI1 = -15 °CA. This is because the cylinder temperature and pressure are lower during combustion when the main injection time is early, while a later main injection time leads to inadequate fuel-air mixing and a delayed combustion phase.
Mao, Jianshu, Zhang, Yixiao, Ma, Yue, Ma, Xiao, Wang, Zhi, Wang, Zhenqian, Shuai, Shijin
Development of Oxygenated Diesel Fuel and Impact on Vehicle Performance2024-01-23744/9/2024
World is moving towards cleaner, greener and energy efficient fuels. The rapid increase in the consumption of petroleum fuel has led to twin problem of air pollution and energy security. India being a developing nation, fuel demand and consumption in various industries, especially in road transport sector has been rising continuously. Fossil fuels are the main source of energy and approximately 85% of domestic need met through import of crude oil. The increasing fuel consumption has created interest for the blending of biofuels in conventional fuel and renewable fuels also. Among biofuels ethanol is one of them and preferable choice for blending in gasoline which is a fuel for spark ignition engines and flex fuel vehicles. As such ethanol/methanol cannot be used in compression-ignition diesel engines without engine modifications due to inherent low cetane number and lubricity of alcohols. Therefore, fuel consisting of certain concentrations of alcohols such as methanol/ethanol in diesel blends is being promoted. The lower alcohols (methanol/ethanol) are not miscible in diesel due to their polarity differences. An additive package is essential for the solubility and stability of alcohol (methanol/ethanol) in diesel phase or diesel blends. Since diesel fuel pumps operate at much higher pressure (up to 220MPa in high-pressure diesel fuel pumps) than the gasoline pumps, oxygenated diesel blends must impart adequate lubricity to metallic parts of fuel delivery system and engine. Lubricity is the one of the important property of diesel specifications (IS: 1460-2017) and appropriate dosing of additive package is compulsory to maintain the specifications of oxygenated diesel blends / alcohol-diesel blends. To tackle the low cetane number, lubricity issue and stability of alcohol-diesel blends, suitable chemistry and dosage of additive package was optimized. Fuel properties of conventional diesel vis-a-vis oxygenated diesel blends having methanol/ethanol up to 15% (v/v) along with appropriate additive package comprising of lubricity improver (LI), cetane improver (CI) and corrosion inhibitor were studied. In this paper, the detailed critical properties of conventional diesel versus oxygenated diesel blends are discussed.
Chakradhar, Maya, Chakrahari, Kiran K., Prakash, Shanti, Raj, Justin, Arora, Ajay, Maheshwari, Mukul, Harinarain, Ajay
Impact of a Split-Injection Strategy on Energy-Assisted Compression-Ignition Combustion with Low Cetane Number Sustainable Aviation Fuels2024-01-26984/9/2024
The influence of a split-injection strategy on energy-assisted compression-ignition (EACI) combustion of low-cetane number sustainable aviation fuels was investigated in a single-cylinder direct-injection compression-ignition engine using a ceramic ignition assistant (IA). Two low-cetane number fuels were studied: a low-cetane number alcohol-to-jet (ATJ) sustainable aviation fuel (SAF) with a derived cetane number (DCN) of 17.4 and a binary blend of ATJ with F24 (Jet-A fuel with military additives, DCN 45.8) with a blend DCN of 25.9 (25 vol.% F24, 75 vol.% ATJ). A pilot injection mass sweep (3.5-7.0 mg) with constant total injection mass and an injection dwell sweep (1.5-3.0 ms) with fixed main injection timing was performed. Increasing pilot injection mass was found to reduce cycle-to-cycle combustion phasing variability by promoting a shorter and more repeatable combustion event for the main injection with a shorter ignition delay. For both fuels, dwells between 2.0 and 2.5 ms resulted in the lowest variability. For these dwells, the pilot injection cumulative heat release at the main injection timing is maximized, resulting in more rapid ignition of the main injection. Emissions results suggest that mixing-controlled combustion of the main injection is achievable with higher pilot masses at injection dwells between 2.0 and 2.5 ms as indicated by an increase in filter smoke number at these conditions.
Stafford, Jacob, Amezcua, Eri, Miganakallu Narasimhamurthy, Niranjan, Kim, Kenneth, Kweon, Chol-Bum, Rothamer, David
Innovative Catalysts for Biodiesel Generation from Edible Oils: Paving the Way for Cleaner Automobiles2023-01-51252/23/2024
The study aims to produce biodiesel from waste cooking oil and compare the effects of two different catalysts (KOH and CaO) on the transesterification process. Homogeneous catalysts and heterogeneous catalysts are the two types of catalysts used in the transesterification process to produce biodiesel. In the present investigation, homogeneous catalysts KOH and heterogeneous catalyst CaO are used in the transesterification reaction. Catalysts are used to accelerate the reaction and increase reaction efficiency. The reaction temperature is set at 65°C. A methanol-to-waste cooking oil ratio of 6:1 is used for KOH and 8:1 for CaO. The catalyst amount is maintained at 2% of the weight of palmitic acid relative to the weight of waste cooking oil. The reaction time is 150 minutes for KOH and 240 minutes for CaO catalysts. The blends include B50C (50% biodiesel with CaO as catalyst and 50% conventional diesel fuel), B50K (50% biodiesel with KOH as catalyst and 50% conventional diesel fuel), B100C (100% biodiesel with CaO as catalyst), and B100K (100% biodiesel with KOH as catalyst). The characteristics of the blends are assessed through the measurement of properties like viscosity, density, cetane number, and flash point. Biodiesel produced with heterogeneous catalyst (CaO) has a higher flash point and increased viscosity. It may be related to a less heterogeneous catalyst remaining in biodiesel fuel. The experimental test results indicate that biodiesel produced with heterogeneous catalyst (CaO) showed more power than its counterpart. The GHG emission (CO2) is slightly higher for B50C & B100C. In the case of NOx emissions, it is higher for blends and particularly for B50C & B100C as the flash point is higher leading to increased combustion temperature.
Devan, P.K., Balasubramanian, M., Madhu, S., Prathap, P.
Use of Artificial Neural Network to Develop Surrogates for Hydrotreated Vegetable Oil with Experimental Validation in Ignition Quality Tester04-17-02-00112/1/2024
This article presents surrogate mixtures that simulate the physical and chemical properties in the auto-ignition of hydrotreated vegetable oil (HVO). Experimental investigation was conducted in the Ignition Quality Tester (IQT) to validate the auto-ignition properties with respect to those of the target fuel. The surrogate development approach is assisted by artificial neural network (ANN) embedded in MATLAB optimization function. Aspen HYSYS is used to calculate the key physical and chemical properties of hundreds of mixtures of representative components, mainly alkanes—the dominant components of HVO, to train the learning algorithm. Binary and ternary mixtures are developed and validated in the IQT. The target properties include the derived cetane number (DCN), density, viscosity, surface tension, molecular weight, and volatility represented by the distillation curve. The developed surrogates match the target fuel in terms of ignition delay and DCN within 6% error range. This investigation will be of value to developing high-fidelity models to investigate HVO combustion and spray behavior. This will be beneficial to researchers advancing the design and development of compression ignition engines to efficiently operate on renewable fuels such as HVO.
Alkhayat, Samy, Joshi, Gaurav, Henein, Naeim
Effect of Diesel-Ethanol Blends on the Performance and Emissions of a CI Diesel Engine Suitable for Stationary Application2024-26-00781/16/2024
Ethanol, being a bio-based alternate fuel, is one of the most promising fuels for blending with diesel for emissions reduction, primarily due to its oxygenated nature, which results in lower carbon content than diesel. Under this research work, various ethanol-diesel (ED) blends have been developed for investigation. Additives were developed to address the problem of corrosion, cetane number reduction, and blend stability. A detailed physico-chemical characterization was performed, and all the blends were subjected to the stability test at various temperatures. Subsequently, detailed experiments were conducted to understand ethanol- blended diesel fuels combustion and engine-out emission characteristics. The performance of the tested engine with ethanol blending remained at par with the baseline diesel; however, a reduction in the PM and gaseous emissions established ethanol blend as a favourable fuel solution for the tested CI engine. Experimental results indicate that blending ethanol in diesel leads to 7% reduction of the cycle NOx emissions (for 20% blend) as compared to the baseline diesel; however, HC and CO were observed to have an increasing trend. A significant reduction of PM (~32%) was observed with 20% ethanol blending. The thermal efficiency improved by 6% maximum with 20% ethanol blend at full load. A meticulous analysis of the combustion data indicated no significant change in the engine in-cylinder pressure values and the start of injection from baseline diesel to ethanol blends at full load condition. However, at part load operation (at and below 50% load), peak firing pressure was reduced up to 6%, and the start of injection and combustion got retarded by ~2 deg crank angle. 5% ethanol blend came out as optimum for quick implementation in the existing engine perspective. Nonetheless the additional HC/CO emissions might have to be dealt with by a catalytic converter.
Garg, Rahul, Mukherjee, Nalini, Viswanath, Chithra, Choudhary, Vasu, Newalkar, Bharat, Nene, Devendra, Kusumba, Manoj
Impacts on combustion from the metal oxide nanoparticles use as an additive in biodiesel: literature review2023-36-01191/8/2024
Although pure biodiesel is used in diesel engines, some challenges, such as higher density, lower cetane number, and lower calorific value, prevent it from completely replacing conventional fossil diesel. Therefore, the addition of compounds aimed at improving the biodiesel combustion process or improving its physicochemical properties is a fundamental issue in using them in pure form or in high proportions in engines, thereby maintaining the performance of such equipment. An alternative that has been studied in recent years is the addition of nanoparticles to biodiesel, which act as catalysts in the combustion process. This study examined in detail the influence of nanoadditives on the performance, combustion, and emissions characteristics of the CI engine. Furthermore, it will discuss the challenges and potential future directions in the utilization of nanoparticles to improve the use of biodiesel in CI engines. The reviewed articles show that the addition of nanoparticles to biodiesel can improve the thermal efficiency of the engine, reduce fuel consumption, carbon monoxide, unburned hydrocarbons, and nitrogen oxides (NOX) emissions due to the catalytic effect of metallic oxide nanoparticles. As a result, the activation temperature of carbon combustion is reduced and, therefore, the oxidation rate of hydrocarbons is increased, promoting more complete combustion. Thus, the use of nanoparticle catalysts can be considered a promising method to optimize the performance of compression ignition engines operating on biodiesel.
Rosa, Josimar Souza, Smaniotto, Marcos Moresco, Telli, Giovani Dambros
Investigation of Performance of Fischer-Tropsch Coal-to-Liquid Fuel, IPK, in a Common Rail Direct Injection Compression Ignition Research Engine with Varying Injection Timing2023-01-164310/31/2023
An investigation of the performance and emissions of a Fischer-Tropsch Coal-to-Liquid (CTL) Iso-Paraffinic Kerosene (IPK) was conducted using a CRDI compression ignition research engine with ULSD as a reference. Due to the low Derived Cetane Number (DCN), of IPK, an extended Ignition Delay (ID), and Combustion Delay (CD) were found for it, through experimentation in a Constant Volume Combustion Chamber (CVCC). Neat IPK was analyzed in a research engine at 4 bar Indicated Mean Effective Pressure (IMEP) at three injection timings: 15°, 20°, and 25° BTDC. Combustion phasing (CA50) was matched with ULSD at 10.8° and 16° BTDC. The IPK DCN was found to be 26, while the ULSD DCN was significantly higher at 47 in a PAC CID 510. In the engine, IPK’s DCN combined with its short physical ignition delay and long chemical ignition delay compared to ULSD, caused extended duration in Low Temperature Heat Release (LTHR) and cool flame formation. It was found in an analysis of the Apparent Heat Release Rate (AHRR) curve for IPK that there were multiple Negative Temperature Coefficient (NTCR) regions before the main combustion event. The High Temperature Heat Release (HTHR) of IPK achieved a greater peak heat release rate compared to ULSD. Pressure rise rate for IPK was observed to increase significantly with increase in injection timing. The peak in-cylinder pressure was also greater for IPK when matching CA50 by varying injection timing. Emissions analysis revealed that IPK produced less NOx, soot, and CO2 compared to ULSD. CO and UHC emissions for IPK increased.
Soloiu, Valentin, Willis, James, Weaver, Amanda, O'Brien, Brandon, Dillon, Nicholas, Davis, Zachary
Ignition and Combustion Controls of Synthetic Fuel using Diesel Engine with Variable Valve Timing System [First Report]2023-32-00609/29/2023
Because the transportation industry uses fossil fuels as much as 1/4 of the total, CO2 emission from transport sector should be reduced. Therefore, carbon neutral (CN) fuel has been attracted attention. However, hydrogen and ammonia have low energy density and are difficult to be stored and transported. In this study, synfuel produced by Fischer-Tropsch (FT) reaction. This fuel is produced with carbon dioxide absorbed from the direct air capture and electricity derived from renewable energy, so it is possible to achieve CN. However, FT fuel tends to have less aromatics and a higher cetane number than diesel fuel. Therefore, excessive early ignition occurs at low speed and low load in application to diesel engine. The purpose of this study is to suppress early ignition by controlling the amount of air flowing into the cylinder. The numerical results showed that the ignition timing and combustion could be controlled using Miller cycle by late intake valve closing (LIVC). In addition, by controlling the ignition timing with LIVC, it became possible to prolong the ignition delay period, and premixed charge compression ignition (PCCI) combustion was realized in the low-speed low-load region. This combustion improved indicated mean effective pressure with high degree of constant volume. Additionally, decrease in fuel-rich zones derived from long ignition delay period reduced NOx and soot emissions. From the above, the possibility of improving combustion and exhaust emission performances by applying the Miller cycle using LIVC when using FT fuel was demonstrated.
Sumida, Yo, Terada, Masaya, Kawano, Daisuke
An Optimized, Data-Driven Reaction Mechanism for Dual-Fuel Combustion of Ammonia and Diesel Primary Reference Fuels2023-32-01019/29/2023
The possibility to operate current diesel engines in dual-fuel mode with the addition of an alternative fuel is fundamental to accelerate the energy transition to achieve carbon neutrality. The simulation of the dual- fuel combustion process with 0D/1D combustion models is fundamental for the performance prediction, but still particularly challenging, due to chemical interactions of the mixture. The authors defined a novel data-driven workflow for the development of combustion reaction mechanisms and used it to generate a dual-fuel mechanism for Ammonia and Diesel Primary Reference Fuels (DPRF) suitable for efficient combustion simulations in heavy duty engines, with variable cetane number Diesel fuels. A baseline reaction mechanism was created by merging the detailed ammonia mechanism by Glarborg et al. with reaction pathways for n- hexadecane and 2,2,4,4,6,8,8-heptamethylnonane from a well-established multi-component fuel mechanism. To define its target validity space, a standardized database of experimental measurements was developed which covers ignition delay times and species concentration profiles in shock tubes, rapid compression machines, and jet stirred reactors. Standardized experimental data served for both mechanism reduction, performance comparison of the optimized mechanism, and a source for simulation input. First, Element Flux (EF) Analysis was run to assess the activity coefficient of each species, and to define a set of reduced mechanisms; a 120-species, 1147 reactions was chosen as the target size and further optimized. During the genetic optimization, the reaction rates of the most relevant reactions were optimized, within uncertainty bounds gathered from the experimental literature. The merit function was evaluated as a multi-objective formulation that compared performance at all experiments. The final mechanism showed noticeable accuracy improvements over the baseline “full” mechanism, with significantly smaller size. The generalized methodology also demonstrated successful mechanism development with little user input, and paved the way for further mechanism improvement and expansion to other target fuels.
Perini, Federico, Reitz, Rolf D., Fiorini, Niccolò, Innocenti, Alessandro, Latinov, Matteo, Vichi, Giovanni
Designing High-Performance Fuels through Graph Neural Networks for Predicting Cetane Number of Multicomponent Surrogate Mixtures2023-32-00529/29/2023
Cetane number (CN) is an important fuel property in designing high-performance fuels in recently diversifying compression ignition engines. We introduce graph neural networks (GNNs) that predict CNs of multicomponent surrogate mixtures when only 2D structures and mole fractions of molecules are given. It considers the influences of mixing multiple components and their chemical structures on CN, reproducing the non-linear blending behavior observed for certain mixtures. We trained the GNNs using the CNs of 1,143 mixtures, and reliable accuracy was achieved with mean absolute errors of 3.4-3.8 from the cross-validation. Lastly, we analyzed the chemical structural effects on non-linear blending behavior.
Kim, Yeonjoon, Kumar, Sabari, Cho, Jaeyoung, Naser, Nimal, Ko, Wonjong, St. John, Peter C., McCormick, Robert L., Kim, Seonah
Thermal efficiency improvement in twin shaped semi- premixed diesel combustion with a combustion chamber dividing fuel sprays and optimization of fuel ignitability2023-32-00519/29/2023
The authors have reported significant smoke reduction in twin shaped semi-premixed diesel combustion with a newly designed combustion chamber to distribute the first and the second sprays into upper and lower layers. However, the first stage premixed combustion tends to advance far from the TDC, resulting in lowering of thermal efficiencies. In this report, improvement of thermal efficiency by optimizing the combustion phase with lower ignitability fuels was identified with the divided combustion chamber. The experiment was conducted with four fuels with different cetane numbers. The first stage premixed combustion can be retarded to the optimum phase with the fuel with cetane number 38, establishing high efficiencies.
Inaba, Kazuki, Kobashi, Yoshimitsu, Shibata, Gen, Ogawa, Hideyuki
On-Board Fuel Sensing for UAS and Ground Vehicle Applications2024-01-41288/10/2023
The variability in fuel, particularly for fuel blends containing sustainable aviation fuels (SAFs), emphasizes the importance of understanding fuel properties for optimizing engine performance. This paper introduces spectroscopic fuel sensors capable of real-time estimation of jet fuel properties, mainly derived cetane number (DCN). While initially developed for unmanned aircraft systems (UAS), the paper explores their potential in ground vehicle applications: enhancing engine performance through sensing for feed-forward control and fuel property monitoring at fuel depots. The fuel sensing technologies are based on spectroscopic techniques coupled with machine learning (ML) approaches. The combination of these techniques demonstrates a promising solution for a wide spectrum of fuel applications.
Patel, Dev B., Sutar, Ashish, Abraham, Abhinav, Ambre, Dhananjay, Brezinsky, Kenneth, Lynch, Patrick T., Okada, Haruna, Stafford, Jacob M., Miganakallu, Niranjan, Sanders, Scott, Rothamer, David, Mayhew, Eric, Kim, Kenneth S.
Numerical Investigation of the Effects of Physical Properties on Spray Characteristics and NVH Characteristics2023-01-11275/8/2023
For liquid fueled engine, the fuel atomization affects fuel’s evaporation, combustion, noise and vibration characteristics eventually. In this study, the effects of fuel species on the internal flow and near field primary breakup characteristics of a nozzle “Spray C” are investigated. Based on the framework of OpenFOAM, the newly developed solver which coupled cavitation model and the multifluid-quasi-VOF (Volume-of-Fluid) model, and combines the LES (Large Eddy Simulation) are applied to simulate the nozzle inner flow and near field jet breakup when using diesel and biodiesel respectively. The transient characteristics of nozzle inner flow and near field spray of two different fuels were analyzed, and the variation of axial pressure and velocity of nozzle was obtained. The simulation results show that the cavitation of biodiesel with high viscosity and low saturated vapor pressure develops slower and weaker. At the same time, due to the high viscosity of biodiesel, the flow velocity of the jet liquid column is slightly smaller than that of diesel, which makes the velocity difference between gas and liquid slightly smaller, and so is the drag force, resulting in the jet breakup penetration distance and turbulence disturbance that is not as strong as diesel. And the high density, viscosity and cetane number of biodiesel results in less vibration and noise compared to diesel.
Liu, Canxu, Dang, Yongjie, Xi, Xi, Zhang, Runqi, Li, Wenfei, Liu, Hong
Development of Data-Driven Models for the Prediction of Fuel Effects on Diesel Engine Performance and Emissions04-16-03-00204/20/2023
A modelling tool has been developed for the prediction of fuel effects on the performance and exhaust emissions of a heavy-duty diesel engine. Recurrent neural network models with duty-cycle, engine control, and fuel property parameters as inputs were trained with transient test data from a 15-liter heavy-duty diesel engine equipped with a common-rail fuel injection system and a variable geometry turbocharger. The test fuels were formulated by blending market diesel fuels, refinery components, and biodiesel to provide variations in preselected fuel properties, namely, hydrogen-to-carbon (H/C) ratio, oxygen-to-carbon (O/C) ratio, derived cetane number (CN), viscosity, and mid- and end-point distillation parameters. Care was taken to ensure that the correlation between these fuel properties in the test fuel matrix was minimized to avoid confounding model input variables. The test engine was exercised over a wide variety of transient test cycles during which fuel rail pressure, injection timing, airflow, and recirculated exhaust gas flow were systematically varied. The resulting models could predict the transient engine torque and fuel consumption, and nitrogen oxide (NOx), soot, carbon monoxide (CO), total hydrocarbon (THC), and carbon dioxide (CO2) exhaust emissions with good accuracy, indicating that the limited number of fuel property parameters selected as model inputs was sufficient to capture the fuel-related effects. The modelling tool can also be used to estimate the relative contributions from changes in the individual fuel inputs to changes in exhaust emissions, and this is illustrated by means of an example blending study with crude-derived diesel fuel, biodiesel, and paraffinic gas-to-liquid (GTL) diesel fuel. This type of novel numerical analysis provides insights into fuel effects which are very difficult to achieve experimentally due to the high degree of intercorrelation between fuel properties that is usually present.
Schaberg, Paul, Harms, Thomas
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