Browse Topic: Dual fuel engines

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Experimental Investigation on Unburned Methanol and Formaldehyde Emissions from a Direct-Injection Diesel / Methanol Dual-Fuel Engine2026-99-16467/24/2026
For large-bore marine methanol / diesel dual-fuel engines, this study investigates the formation characteristics of unregulated emissions through experimental methods and explores the mechanisms by which engine load and injection timing influence the emissions of unburned methanol and formaldehyde. The study was carried out on a supercharged intercooled inline six-cylinder engine, and Fourier Transform Infrared Spectroscopy (FTIR) was used to monitor the exhaust composition in real time. The study shows that methanol released in the exhaust is due to the incomplete combustion of the methanol fuel. In the combustion process of methanol fuel, formaldehyde mainly arises from two pathways, the first of which is the partial oxidation of methanol inside the cylinder; secondly, the unburned methanol in the exhaust gas oxidizes in the exhaust pipe to generate formaldehyde. As the load increased from 25% to 100%, the unburned methanol emissions decreased by 29%, and formaldehyde emissions decreased by 71%. This is mainly attributed to the enhanced oxidation reaction and reduced wall crevice effect due to the increased combustion temperature. Methanol injection timing optimization was effective in controlling unregulated emissions, with methanol emissions lower at -7° CA ATDC and formaldehyde emissions reaching larger values under this condition. Delaying the diesel injection to -16°CA ATDC led to a 38% increase in unburned methanol emissions, caused by fuel spray interactions and longer stagnation, whereas formaldehyde emissions showed minimal change.
Jiang, Yuqi, Li, Hongmei, Zhang, Wenzheng, Li, Xiao, Zheng, Liang, Meng, Yangqian, Gu, Xianan, Hua, Hanqing
Experimental and Computational Study on Combustion and Performance Characteristics of an Ammonia–Diesel Dual-Fuel Engine under Low Load Conditions2026-01-50627/22/2026
Ammonia is receiving heightened attention as a carbon-neutral and hydrogen energy carrier alternative fuel for compression ignition engines. However, replacing diesel with ammonia poses significant challenges due to its low reactivity and slow-burning nature, particularly at low-load conditions. This study investigated the effect of ammonia energy share (AES) on the combustion characteristics and performance of an ammonia–diesel dual-fuel (ADDF) compression ignition engine operating under low loads and at a constant speed of 1800 RPM. The experiments were conducted at three different loads: 6 Nm, 13.5 Nm, and 18 Nm, corresponding to 11%, 25%, and 33% of full load, respectively. At each load, the AES was incrementally increased, ranging from zero to its maximum limit, while maintaining the COV of IMEP below 3% to ensure stable combustion. Furthermore, CFD simulations were performed using a CONVERGE CFD model of the engine to analyze the in-cylinder thermal and chemical behavior, and the model was validated against the experimental data. The experimental results showed that the AES reached 40%, 58%, and 61% for engine loads of 6 Nm, 13.5 Nm, and 18 Nm, respectively. Increasing AES reduced the mean in-cylinder temperature and peak cylinder pressure, and shifted the peak pressure location toward the expansion stroke. Combustion phasing was delayed, and combustion duration increased with higher ammonia substitution. CFD analysis revealed weaker high-temperature and OH reaction zones, along with reduced OH and H radical activity, and increased persistence of NH2 and HO2 evolution at higher AES, indicating slower oxidation of the ammonia-containing mixture. The results highlight the challenges associated with high-ammonia operation at low loads and provide deeper insight into the combustion processes governing ADDF engine performance.
Sardar, Gobinda, Kishore, Kislay, Pradeep, P., Mittal, Mayank
Methane Emission Mitigation in Large-Bore Dual-Fuel Engines via Negative Valve Overlap Diesel Injection: Thermochemical Pathways and Reactivity Control2026-37-00456/9/2026
Low-load natural gas–diesel reactivity controlled compression ignition (RCCI) in medium-speed marine engines is constrained by an insufficient charge thermal state. This limitation leads to partial fuel oxidation, producing high methane emissions. This work evaluates the use of negative valve overlap (NVO) combined with NVO diesel injection as an in-cylinder reactivity enhancement strategy. The simulation study was performed using the University of Vaasa’s advanced thermo-kinetic multi-zone model (UVATZ), extended for reactive simulations during NVO. The extended framework was validated against test-bench data from a prototype Wärtsilä 6L20 dual-fuel engine operating in RCCI mode. The baseline low-load operating point for reforming simulations was defined by reducing the intake manifold temperature to replicate conditions close to partial misfire with 52% combustion efficiency. The parametric sweeps of NVO injection timing and ratio showed that the strategy can be used for in-cycle fast thermal management, effectively restoring complete combustion on an individual cycle basis. In simulated conditions, the best performance was obtained with an NVO injection ratio of 0.3, with the injection scheduled before top dead center. In contrast, increasing the NVO fraction beyond ~0.3 provided no benefit and led to complete misfire due to excessive reduction of main-event high-reactivity fuel. The simulations revealed a coupled thermal–chemical control mechanism. Early NVO injections stabilize combustion through recompression heat release and an increased next-cycle intake valve closing temperature. Sufficiently late injections stabilize combustion by carrying unreacted diesel into the subsequent cycle. Injections near NVO TDC primarily undergo fuel conversion to CO, H2O, and unsaturated light/mid-range hydrocarbons with negligible thermal boost, yielding an overall reactivity deficit.
Soleimani, Amir, Nurmi, Mikael, Hunicz, Jacek, Kim, Jeyoung, Hyvonen, Jari, Mikulski, Maciej
Effect of EGR Rate on Cyclohexanol-Diesel Dual-fuel Engines2026-99-17095/22/2026
To reduce high NOx emissions from diesel-cyclohexanol blends, this study employed a marine medium-speed diesel engine as the experimental platform. An in-cylinder combustion model was developed and meshed using AVL - FIRE software, with model validity validated against experimental data. Tests were conducted at four load conditions (25%, 50%, 75%, and 100% load) with a 30% cyclohexanol blend (C30) and four EGR rates (0%, 7.5%, 10%, and 12.5%) to analyze combustion characteristics, emissions, and fuel economy. The results showed that the introduction of EGR had a striking inhibitory effect on NOx emissions. At 100% load with 12.5% EGR rate, NOx emissions were substantially reduced compared to baseline operation without EGR. However, EGR implementation led to delayed ignition timing, reduced in-cylinder pressure, and worsened fuel economy. Therefore, an appropriately calibrated EGR strategy can effectively reduce NOx emissions, though it requires optimization to mitigate adverse effects on combustion performance and efficiency.
Liu, Yuchen, Yang, Chenxi, Fan, Jinyu, Chen, Ke, Ye, Zixiao, Huang, Jialiang
TOC99-08-01-0TOC2/11/2026
TOC
Tobolski, Sue
Research on Active Predictive Speed Control of Dual-Fuel Engine for Hardware Real-Time Applications03-19-01-00042/9/2026
The present article proposes an active observation speed prediction control algorithm architecture for embedded applications, with the aim of addressing the problems of complex operating conditions, strong perturbations, and high control real-time requirements of high-pressure direct injection (HPDI) dual-fuel engines. A nonlinear speed prediction model with diesel and natural gas injection mass as inputs has been established, and the nonlinear model predictive control (NMPC) method is used to realize the optimized control of engine speed. In order to enhance the operational efficiency of the algorithm on the embedded platform, a system has been developed that includes an event triggering mechanism and a warm-start strategy. These mechanisms work in tandem to dynamically adjust the computation cycle. Additionally, a torque reduced-order expansion state observer (RESO) has been integrated to improve the accuracy of perturbation estimation and computational efficiency. The model-level experiments and hardware verification were carried out under the sudden load change operating condition and World Harmonized Transient Cycle (WHTC) test, respectively. The simulation results demonstrate that the proposed optimization strategy can effectively reduce the peak-to-peak value of speed control error to 118.73 rpm and shorten the stabilization time to 3.48 s. Furthermore, the tracking accuracies of the controller on the speed and torque targets in the hardware test reach 0.994 and 0.997, respectively, thereby substantiating the high accuracy and robust performance of the proposed algorithm.
Yang, Xinda, Li, Yunhua, Chen, Dongdong, Li, Yao, Zhang, Shutao, Zhao, Feiyang, Yu, Wenbin
Performance Optimization of 2 Cylinder Flex Fuel Engine for Small Commercial Vehicle – A STEP TOWARDS SUSTAINABILITY2026-26-01191/16/2026
Increasing ethanol blending in gasoline is significant from both financial (reducing dependency on crude oil) and sustainability (overall CO2 reduction) points of view. Flex Fuel is an ethanol-gasoline blend containing ethanol ranging from 20% to 85%. Flex Fuel emerges as an exceptionally advantageous solution, adeptly addressing the shortcomings associated with both gasoline and ethanol. Performance optimization of Flex Fuel is a major challenge as fuel properties like knocking tendency, calorific value, vapour pressure, latent heat, and stoichiometric air-fuel ratio change with varying ethanol content. This paper elaborates on the experimental results of trials conducted for optimizing engine performance with Flex Fuel for a 2-cylinder engine used in a small commercial vehicle. To derive maximum benefit from the higher octane rating of E85, the compression ratio is increased, while ignition timing is optimized to avoid knocking with E20 fuel. For intermediate blends, ignition timing is suitably interpolated. Fuel injection pressure is increased to address the higher fuel flow requirement, and a fuel heater is added to address cold starts with E85 fuel. Ethanol content detection is done through software, and by suitable interpolation, fuelling and ignition timing are optimized for the entire range of Flex Fuel in a single calibration file. Engine performance with E20 & E93 fuel is optimized considering all mechanical and thermal limits of the engine through various iterations. The experimental results are analysed using the first principle method.
Kulkarni, Deepak, Malekar, Hemant A, Upadhyay, Rajdip, Katkar, Santosh, Undre, Shrikant
Unveiling the Dynamics of Methanol-Diesel Dual Direct Injection Compression Ignition Combustion: A Synergistic Experimental and Numerical Study2026-26-01101/16/2026
The pressing global need for de-fossilization of the transport sector, especially within the heavy-duty segment, has intensified the exploration of alternative clean fuels. In this context, methanol gained traction due to their renewable production pathways, carbon-neutrality, and are being highly promoted by the Indian government to reduce CO2 emissions. Dual direct injection compression ignition (DDICI) is an effective combustion strategy to use methanol in heavy-duty engines, which combines the advantage of high-efficiency compression ignition with the clean-burning potential of methanol. In contrast to spark-ignited premixed methanol engines, this strategy involves a diffusion combustion of the methanol flame, thereby eliminating knocking and enabling running with high compression ratios. This experimental and numerical study presents a comprehensive investigation into the DDICI strategy using methanol as primary fuel and diesel as a pilot for ignition assistance. The work benchmarks the methanol DDICI operation against baseline diesel operation, catering the required combustion chamber modifications, fuel injection strategy, system layout and capturing key metrics like thermal efficiency and emissions. The numerical study details the effect of swirl spray orientation, and positioning of the pilot injector, on the charge distribution and the ignition. The 3D-CFD models used for the simulation model are well validated against experimental results to capture in-cylinder combustion dynamics and emission trends. The experimental results demonstrate that methanol DDICI achieves a thermal efficiency improvement of up to 2.5-3.0 % at high load with NOx reduction of about 50 % at similar exhaust gas recirculation (EGR) ratio compared to the baseline diesel. Additionally, it demonstrated soot-free combustion and lower in-cylinder temperatures reducing thermal stresses. The introduction of swirl led to improved mixture formation, promoted gradual ignition and enhanced post-flame oxidation, thereby reducing CO emissions. Furthermore, the simulation results revealed that the reduced spatial separation between diesel and methanol spray plume facilitates faster ignition and smoother combustion. In this regard, the stagger angle of 12.5° with 9-hole nozzle resulted in lower maximum pressure rise rate compared to 22.5°, with similar levels of thermal efficiency and NOx emissions.
Singh, Inderpal, Dhongde, Avnish, Raut, Ankit, Güdden, Arne, Emran, Ashraf, Berry, Sushil
Development of Flex Fuel Engine for Indian Market2026-26-01171/16/2026
This paper presents the methodology and outcomes of modifying a 1.2L naturally aspirated (NA) engine to enable flex-fuel compatibility, targeting optimal performance with ethanol blends ranging from E20 to E100. Ethanol is being increasingly promoted due to its potential to reduce greenhouse gas emissions and to provide an additional source of income for farmers. As per the road map for Ethanol blending released by Govt. of India, there has been continuous increase in blending of ethanol in gasoline. An initial target of 20% ethanol blending in gasoline by April 2025 has already been achieved. This work is in alignment with the broader push for development of flex-fuel vehicles, which necessitates engine adaptations capable of operating on varying ethanol blends. The primary objective was to upgrade the engine, which can give optimum performance with both lower range of ethanol blends starting from E20 as per IS 17021:2018 standard till higher blends of up to E100 as per IS 17821:2022. The engine upgrade included several key modifications such as material upgradation of components directly coming in contact with fuel for ethanol resistance, optimization of the compression ratio, introduction of heated fuel rail system for cold start and redesign of intake camshaft to ensure compatibility and performance with ethanol-blended fuels. Additionally, the engine management system (EMS) was recalibrated with dedicated maps tailored to various ethanol blend levels, enabling efficient and reliable operation across a wide range of fuel compositions
Tyagarajan, Sethuramalingam, Pise, Chetan, Kavekar, Pratap, Agarwal, Nishant Kumar
A Study on Combustion Process in Hydrogen/Hydrotreated Vegetable Oil Dual-Fuel Operation Using Hydroxyl Radical Chemiluminescence03-18-08-00501/7/2026
This study investigated the combustion processes in hydrogen dual-fuel operation using hydrotreated vegetable oil (HVO) and diesel fuel as pilot fuels. The visualizations of hydrogen dual-fuel combustion processes were conducted using hydroxyl radical (OH*) chemiluminescence imaging in an optically accessible rapid compression and expansion machine (RCEM), which can simulate a compression and expansion stroke of a diesel engine. Pilot injection pressures of 40 and 80 MPa and injection quantities of 3, 6 mm3 for diesel fuel and to match the injected energy, 3.14, 6.27 mm3 of HVO were tested. The total excess air ratio was kept constant at 3.0. The RCEM was operated at a constant speed of 900 rpm, with in-cylinder pressure at top dead center (TDC) set to approximately 5.0 MPa. Results demonstrated that using HVO as pilot fuel, compared to diesel fuel, led to shorter ignition delay and combustion duration. OH* chemiluminescence imaging revealed that longer ignition delays observed with diesel fuel resulted in pilot mixture ignition downstream near the piston bowl wall, followed by flame propagation into the hydrogen–air mixture. In contrast, the shorter ignition delays characteristic of HVO caused the pilot mixture to ignite between the injector and the piston bowl wall, with subsequent flame propagation into the hydrogen premixture.
Mukhtar, Ghazian Amin, Une, Naoto, Horibe, Naoto, Hayashi, Jun, Kawanabe, Hiroshi, Hiraoka, Kenji, Koda, Kazuyuki
Improving Late Pilot Injection Strategy in Dual-Fuel Diesel/Methane Engines through Supercharging and Hydrogen Enrichment03-18-08-004912/24/2025
In this study, a novel dual-fuel combustion strategy is investigated, employing late pilot injection in diesel–methane engines to improve performance and reduce emissions. The engine was first tested with conventional diesel and methane, exploring a wide range of pilot injection timings, injection pressures, and intake boost pressures. Subsequently, experiments were repeated using a methane/hydrogen blend to assess the influence of hydrogen addition. Results show that, when using only methane, delayed pilot injections have minimal effects on engine performance. In naturally aspirated operation, unburned hydrocarbons and carbon monoxide are reduced, while in supercharged conditions, emissions increase; however, they remain within acceptable limits. Nitrogen oxides and particulate matter reach their lowest levels with delayed injection. Introducing hydrogen reduces engine performance and hydrocarbons and carbon monoxide emissions; notably, it suppresses the typical nitrogen oxides increase associated with hydrogen, while also lowering particulate matter. These findings demonstrate that combining late pilot injections with hydrogen addition and supercharging is a promising strategy for improving dual-fuel engine efficiency and emissions, offering a potential pathway toward cleaner combustion.
Carlucci, Antonio Paolo, Strafella, Luciano, Ficarella, Antonio
Effect of Ultra-High Fuel Injection Pressure on Combustion Characteristics, Engine Performance and Pollutant Emissions of a Multi-Cylinder Engine2025-36-021212/18/2025
The concern about CO2 emissions from commercial vehicles powered with internal combustion engines has been motivating research and development projects to reduce the transportation sector carbon footprint. One of the promising alternatives is the use of biofuels associated with high-efficient internal combustion engines, taking advantage of the current infrastructure of car manufacturers and automotive suppliers, as well as of the potential growth in biofuel production. With the stringent emissions regulations, the use of downsized SI engines for passenger cars has driven the adoption of direct injection technology, enabling the use of different fuel injection strategies such as stratified mixtures and multiple injection events, as well as the increase of the compression ratio as a way to improve engine thermal efficiency. This path also led to a gradual increase in injection pressure, aiming to improve spray formation and reduce the formation of particulate matter. In this sense, the implementation of such technology on the Brazilian flex-fuel engine represents an important path to the transport sector decarbonization. However, the use of hydrous ethanol and gasoline-anhydrous ethanol blends on direct injection systems still demands fundamental research to fully understand the potential benefits and drawbacks of higher fuel injection pressures. Within this framework, this work aims to further understand the effect of using ultra-high fuel injection pressures (up to 1000 bar) on engine performance and pollutant emissions of a multi-cylinder prototype engine. Experimental tests with three different injection pressures confirmed the HC and soot emission reduction, as well as improvement on the engine brake thermal efficiency both when fueled with hydrous ethanol and Brazilian gasohol (blend of 27% anhydrous ethanol in gasoline). Due to the lack of dedicated hardware to pressurize and inject ethanol at ultra-high pressures, the durability of the injection components was a major concern during the experimental campaign.
Antolini, Jácson, Zabeu, Clayton Barcelos, Pires, Gustavo Cassares, Polizio, Yuri
Performance Analysis of Methanol- Ethanol Blend Fuel in a Spark-Ignition Flex-Fuel Engine2025-36-014812/18/2025
Flex-fueled vehicles (FFV) dominate the Brazilian market, accounting for over 75% of the national fleet. Ethanol fuel is widely used, primarily in the form of hydrated ethyl alcohol fuel (HEAF). Given the similar physicochemical properties of ethanol and methanol, fuel adulteration is a growing concern, often involving the addition of anhydrous ethanol, methanol, or even water to hydrated ethanol. These adulterants are visually imperceptible and can only be detected through analyses conducted by regulatory agencies using specialized instruments. However, they can significantly affect vehicle performance and accelerate engine component deterioration. The experiment was performed with a small displacement 3-cylinder port fuel injection flex-fuel engine on an engine test bench (dynamometer) and compared when fueled with ethanol and methanol. Data acquisition included combustion pressure, spark plug temperature, torque, air-fuel ratio, fuel flow, spark maps, and the overall effects of methanol adulteration on combustion. The results indicate that engines designed and calibrated to operate with hydrated ethanol exhibit different combustion behaviors when methanol is present in the fuel mixture. Methanol increases combustion pressure and temperature inside the chamber, creating a highly corrosive environment due to both the elevated temperature and the chemical properties of methanol. Fuel consumption increased when methanol was used in the engine calibrated for ethanol. The findings highlight the potential risks associated with fuel adulteration, emphasizing its impact on engine durability, vehicle fuel economy, and maintenance costs.
Mascarenhas, Giovana Rebellato, Gomes, Ederson, Cruz, Diego, Duque, Edson Luciano
Analysis of Combustion Process in HVO-Hydrogen Dual-Fuel Operation Using Simultaneous Imaging of OH* and CH* Chemiluminescence2025-32-005311/3/2025
This study investigated the combustion process in a hydrotreated vegetable oil (HVO)–hydrogen dual-fuel operation using simultaneous imaging of the OH* and CH* chemiluminescence in a rapid compression and expansion machine (RCEM). In this operation, hydrogen served as the primary fuel, ignited by a small quantity of pilot fuel. CH* chemiluminescence was primarily detected in the pilot fuel combustion regions, whereas OH* chemiluminescence was detected in both the pilot fuel and hydrogen combustion regions, enabling the separation of pilot ignition and hydrogen flame propagation. The combustion mechanism was found to proceed through four distinct stages: autoignition of the pilot fuel, combustion of the mixture in the lean pilot fuel region, propagation of the hydrogen–air premixture flame, and flame propagation toward the wall and squish area. Furthermore, the effects of the pilot injection parameters on the combustion characteristics were systematically evaluated by varying the injection quantity, injection pressure, and nozzle specifications (hole diameter and number of holes). Increasing the pilot injection quantity improved the degree of constant volume of combustion but intensified the combustion near the wall, potentially increasing the cooling loss. Reducing the injection pressure shifted the autoignition location toward the center of the piston bowl, potentially reducing cooling loss but prolonging the combustion duration. With smaller injection quantities, fewer nozzle holes resulted in a higher second heat release rate peak, owing to the increased space for hydrogen flame propagation. Conversely, with larger injection quantities, a greater number of nozzle holes led to a shorter combustion duration while maintaining the combustion away from the wall.
Yukitani, Takumi, Une, Naoto, Mukhtar, Ghazian, Horibe, Naoto, Kawanabe, Hiroshi, Koda, Kazuyuki, Hiraoka, Kenji
Analysis of Combustion Characteristics and Performance of a Multi-Cylinder Engine Operating on Syngas/Diesel in Dual-Fuel Mode2025-24-00429/7/2025
Despite improvements in internal combustion engine efficiency, fossil fuel reliance remains a challenge for sustainable energy. Syngas, a hydrogen-carbon monoxide mixture produced from gasification, typically of carbon-based feedstocks, offers a viable transitional fuel due to its compatibility with existing combustion technologies and reduced emissions. However, its low ignition propensity elevated intake temperatures or pressures, a limitation that can be overcome through diesel pilot injection in dual-fuel engine configurations. This study extends prior single-cylinder research to a 1.6 L four-cylinder HCCI engine operating in dual-fuel mode, resembling a Reactivity Controlled Compression Ignition (RCCI) engine. The analysis focuses on cylinder-to-cylinder combustion variation, thermal efficiency, and pollutant emissions, with particular emphasis on the influence of diesel pilot injection timing. Experimental evaluations are conducted across a range of injection timing and Syngas flow rates (100 to 160 L/min). Key metrics include ignition delay, heat release rate, maximum pressure rise rate, coefficient of variation of indicated mean effective pressure, and pollutant emissions. Results indicate that diesel pilot injection timing significantly affects combustion phasing, heat release dynamics, and overall engine efficiency. Advancing or retarding the injection timing alters ignition delay and heat release characteristics, with optimal settings improving Syngas utilization and reducing particulate emissions. These findings highlight the importance of injection strategy optimization for realizing the full potential of Syngas in multi-cylinder engines, supporting their integration into cleaner and more efficient propulsion systems.
El Younsi, Laila, Nelson-Gruel, Dominique
Numerical Analysis of In-Nozzle Flow of Methanol Injectors for Large Marine Two-Stroke Engines2025-24-00699/7/2025
A statistical method for analyzing momentum deflection angles of fuel injectors based on Computational Fluid Dynamics (CFD) simulation of the internal nozzle flow is proposed. This method is especially relevant for large marine two stroke engines where the spray is often deflected due to an eccentric and asymmetric design of the internal injector geometry. Unsteady Reynolds-Averaged Navier-Stokes (URANS) CFD simulations are employed to analyze the internal flow of different cavitating injectors which have four and five nozzle holes, respectively, for a 50 cm bore and a 95 cm bore dual-fuel engine operating on methanol. The in-nozzle flow dynamics vary from one to another significantly. The use of the statistical analysis on the distribution of deflection angles at the fuel nozzle hole exit further assists at explaining differences in measured surface temperatures of the exhaust valve bottom and piston bowl. The corrected spray angles obtained from these in-nozzle simulations also serve as important inputs to the CFD engine combustion simulations for further in-cylinder analysis.
Quist, Nicolai Arent, Matlok, Simon, Pang, Kar Mun, Norman, Thomas Schaldemose, Mayer, Stefan, Walther, Jens Honoré
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
Effects of Varying the Air-Fuel Equivalence Ratio at Different EGR-Rates on a Medium-Speed LNG-Diesel Dual-Fuel Engine2025-24-00419/7/2025
The dual-fuel combustion process, which is offered as a retrofit solution for conventional diesel engines by various manufacturers, represents an option for reducing emissions from internal combustion engines and is already available today. Current dual-fuel engines run on liquefied natural gas (LNG), which is usually of fossil origin. Due to the existing infrastructure and the possibility of producing LNG by means of electrolysis and methanation, LNG can already be produced in a 100% climate-neutral way and thus make a contribution to climate neutrality in the shipping industry. The adoption of exhaust gas recirculation (EGR) systems in the maritime sector became more significant in 2020 following the enforcement of the sulphur emission cap. By lowering the sulphur content in the fuel, technologies in the exhaust tract are also conceivable without the use of expensive scrubber systems. Dual-fuel LNG/diesel engines are typically operated in lean-burn mode to reduce the risk of knocking and to comply with the nitrogen oxide limits in accordance with IMO TIER III. However, one disadvantage of the lean-burn combustion process is climate-damaging methane (CH4) slip due to incomplete combustion. To address this issue, an EGR system can be employed to mitigate nitrous oxides (NOx) emissions and prevent engine knocking at richer air-fuel mixtures, as an alternative to increasing the air-fuel equivalence ratio lambda. In the context of this paper, experimental investigations are conducted on a single cylinder medium speed dual-fuel engine, where EGR rates of up to 35% are examined across various lambda values. The adjustment of lambda is achieved by varying the charge air pressure using an externally driven compressor station for charge air supply. The results of the presented investigations provide insights into the emission reduction potential of a targeted variation in EGR rates and lambda, thus making an important contribution to more environmentally friendly ship propulsion systems.
Seipel, Pascal, Glauner, Manuel, Dinwoodie, Jules, Buchholz, Bert
CFD-Driven Optimization of Diesel Injection for a Hydrogen-Diesel Dual Fuel Engine2025-24-00459/7/2025
Among the alternatives to the use of fossil diesel fuel, dual fuel combustion, leveraging hydrogen as the low-reactivity fuel, represents a promising approach for both reducing pollutant emissions and improving brake thermal efficiency. In addition, this innovative combustion mode requires minimal modifications to the existing Diesel engines architecture. This study was conducted on a Diesel engine (naturally aspirated, 3-cylinder, 1 L, direct injection), properly modified by the authors to operate in dual fuel mode with port fuel injection of hydrogen. A set of experimental data was used to calibrate the 1D and the 3D-CFD models for both Diesel and diesel-hydrogen dual fuel configurations. The AVL FIRE M 3D-CFD software was employed to model diesel injection and combustion, while the gas exchange process was analyzed by GT-Power. The validated 3D-CFD model was then leveraged to optimize the baseline diesel injection strategy in dual fuel mode, minimizing diesel consumption while maintaining stable combustion and comparable performance with respect to the baseline Diesel engine. Notably, the analysis highlights that, at low loads, where hydrogen energy fraction is limited, a diesel injection strategy consisting of two fuel pulses is required to ensure stable ignition. However, as the hydrogen contribution increases, the main injection can be reduced or eliminated, with the pilot injection alone being sufficient to ignite the premixed charge, without compromising engine efficiency. This optimized strategy enabled a simultaneous reduction in diesel usage, up to −62.6%, and a marked decrease in emissions, with the best reductions reaching −62.5% for CO₂, −81.1% for CO, and −31.6% for NOₓ.
Rinaldini, Carlo, Pisapia, Alfredo Maria, Scrignoli, Francesco, Volza, Antonello, Rossetti, Salvatore, Mancaruso, Ezio
Effects of Fuel and Intake Air Temperatures on Ethanol Evaporation under Cold and Warm Conditions in a Diesel-Derived Heavy-Duty SI Engine2025-24-00769/7/2025
Heavy-duty internal combustion engines (ICEs), including those used in agricultural machinery, are undergoing a transition towards renewable fuels to reduce their environmental impact. In a scenario aiming at complete fossil fuel elimination, bioethanol emerges as one of the most promising alternative fuels, gaining particular attention in agricultural applications, where fuel production can be integrated into farm operations. Bioethanol high octane number, elevated latent heat of vaporization, and fast laminar flame speed enable high engine performance while reducing pollutant emissions compared to conventional spark ignition (SI) engines. However, challenges related to ethanol evaporation must be addressed. In this study, a diesel-derived engine was converted to run on pure ethanol in spark ignition mode using a single-point injection (SPI) system. Unlike conventional flex-fuel engines that run on blends of gasoline and ethanol, this configuration was selected to avoid modifications to the cylinder head and enables the complete elimination of the fossil fuels. A 1D numerical model, which takes into account the droplets and film evaporation as well as wall spray impingement was developed in order to investigate the in-cylinder ethanol evaporation at different fuel injection temperatures (25–100 °C), intake air temperatures (25–115 °C) under both cold and warm engine conditions. Under cold conditions, results indicate that intake air temperature has a dominant effect on ethanol vaporization. At 115 °C air temperature and 100 °C fuel temperature, the burned vapor fraction reached 66%, compared to 28% at 25 °C air temperature. Under warm engine conditions, the elevated wall temperatures enable complete evaporation of the liquid film, even when intake air and fuel temperatures are low. These findings highlight the critical role of thermal boundary conditions, especially air and wall temperatures, in optimizing mixture preparation and combustion efficiency. The study provides valuable insights for improving cold start strategies and thermal management in ethanol-fueled heavy-duty engines, promoting reliable and efficient operation.
Perrone, Diego, Falbo, Biagio, Falbo, Luigi, Castiglione, Teresa
Experimental Measurement of Dynamometer Homologation Cycles in a Dual-Fuel Medium-Duty Engine2025-24-00369/7/2025
Dual-fuel engines employing alternative combustion concepts have shown promising results in meeting significant emission reductions while maintaining engine performance. In the medium and heavy-duty transport sectors, where electrification remains challenging, developing low-temperature combustion is still a technological solution for reducing carbon impact. However, most of the results in this research field have been presented under stationary conditions, which still positions the transient operation as a challenge. One of the main reasons has been the lack of a dedicated control system to manage the load transitions and the inoperability of stock turbochargers to satisfy the EGR dilution ratios and boost pressure to sustain dual-fuel combustion. This study employs a modified 7.7 L dual-fuel engine for its operation in transient conditions by incorporating a prototype turbocharger system. The study addresses the recalibration of the engine to introduce modifications to the injection and air management strategies, allowing for a smoother transition between fully premixed and diffusive combustion modes while maintaining low emissions and similar performance. The study identified the transition from 50% to 75% as the most challenging transition from moving from a fully premixed zone with pressure gradients near the physical limits to a more diffusive combustion region in the engine map. After refining the calibration to allow smooth transitions between loads, transient cycle performance under the World Harmonized Stationary Cycle (WHSC) is experimentally measured, progressively increasing load from 50% to 100%. The results under transient tests confirmed that the recalibration successfully enables full-load operation while mitigating combustion instability and excessive emissions. This research advances the understanding of dual-fuel combustion strategies and highlights the potential of dual-fuel engines as a technological solution for its implementation under real-world vehicle applications in the freight transport sector.
Garcia, Antonio, Monsalve-Serrano, Javier, Marco-Gimeno, Javier, Iñiguez, Erasmo
Effect of Ammonia Proportion on the Combustion and Emissions in Ammonia/Diesel Dual-Fuel Engines2025-01-50557/21/2025
This article develops a numerical simulation framework for ammonia/diesel dual-fuel combustion using CONVERGE software. The modeling approach is explained in detail, including theories of numerical computation, mathematical submodels, modeling methodologies, and boundary condition specifications. Based on the developed model, this work investigates the impact of the ammonia fuel ratio on some key combustion and emission characteristics: heat release dynamics, distribution of the in-cylinder temperature field, formation of intermediate combustion species, and pollutant emissions. It provides comprehensive analysis in terms of in-cylinder pressure, mean temperature, heat release rate profile, cumulative heat release, fluctuations in the compositions of n-heptane and ammonia, distribution of the equivalence ratio, turbulent kinetic energy, concentration of OH radicals, formation of formaldehyde, and emissions of pollutants including CO, NOx, N2O, soot, and unburned hydrocarbons (HC) with respect to crank angle. The results showed that the fraction of ammonia fuel is the key to affecting in-cylinder combustion, the development of intermediate and final products, and different pollutant emissions. This work can provide important theoretical guidance and practical suggestions for the development of ammonia/diesel dual-fuel combustion technology, as well as promote effective and green utilization of ammonia in internal combustion engines.
Yu, Wenbin, Wang, Haoyu, Liang, Shuaibo, Wang, Shuning
Ethanol Fuel as Enabler for High-Efficiency and Low-Soot Combustion in Dual-Fuel and Blend Modes03-18-04-00287/16/2025
Global climate initiatives and government regulations are driving the demand for zero-carbon tailpipe emission vehicles. To ensure a sustainable transition, rapid action strategies are essential. In this context, renewable fuels can reduce lifecycle CO2 emissions and enable low-soot and NOx emissions. This study examines the effects of renewable ethanol in dual-fuel (DF) and blend fueling modes in a compression ignition (CI) engine. The novelty of this research lies in comparing different combustion modes using the same engine test rig. The methodology was designed to evaluate the characteristics of various injection modes and identify the inherent features that define their application ranges. The investigation was conducted on a single-cylinder engine equipped with state-of-the-art combustion technology. The results indicate that the maximum allowable ethanol concentration is 30% in blend mode, due to blend stability and regulatory standards, and 70% in DF mode, due to combustion stability and emission concerns. DF mode produces higher THC and CO emissions compared to blend or conventional diesel combustion (CDC) modes. However, ethanol consistently reduces smoke formation across all engine test conditions and fueling modes. At ultra-low-NOx levels (0.5 g/kWh), smoke emissions remain below 0.5 FSN. At the highest ethanol fraction in DF mode (70%), smoke emissions decrease to very low levels (−0.1 FSN), with improvements in thermal efficiency and CO2 emissions. DF mode requires specific injection control strategies to mitigate THC and CO emissions. In blend mode, the highest ethanol fraction (30%) results in CO2 and soot reductions, with CO and THC emissions comparable to CDC.
Belgiorno, Giacomo, Ianniello, Roberto, Di Blasio, Gabriele
Effects of Double Injection Strategy in a Diesel-Ammonia Dual-Fuel Engine2025-01-02066/16/2025
This study investigates the application of a double injection strategy in a single-cylinder marine diesel-ammonia dual-fuel engine retrofitted for experimental analysis. A diesel micro-pilot (MP) injection was used to ignite ammonia combustion, and diesel and ammonia were injected separately into the cylinder through dedicated injectors. The first MP injection timing was fixed at reference injection timing, and both early and late double MP injection strategies were implemented to evaluate their effects on ammonia combustion, engine performance, and exhaust emissions. Under all conditions, the ammonia injection timing remained constant. Early double injection strategies, with the second MP injection occurring before the first, enhanced premixed diesel combustion by raising in-cylinder temperature and pressure. However, this early heat release was ineffective for ammonia evaporation and combustion due to poor timing alignment. In contrast, late double injection strategies, with the second MP injection occurring between +75–105 CAD after reference injection timing, improved ammonia combustion by targeting the diesel spray at unburned ammonia in the squish region near the cylinder liner, where flame quenching typically occurs. Consequently, late MP injections reduced unburned ammonia emissions but led to higher N2O and hydrocarbon emissions due to slower oxidation rates in the squish region. Additionally, thermal efficiency declined due to decreased work conversion efficiency. Unburned ammonia above a certain level was detected under all conditions, primarily due to injector asymmetry, which led to incomplete combustion in specific regions of the cylinder. These findings underscore the importance of optimizing diesel pilot injection timing to enhance ammonia combustion while managing trade-offs in emissions and efficiency in dual-fuel engines.
Park, Chansoo, Jang, Ilpum, Park, Cheolwoong, Kim, Minki, Park, Gyeongtae
Combustion and Emission Characteristics of Marine Ammonia-Diesel Dual Fuel Engine with Micro-Pilot Injector Change2025-01-02356/16/2025
Recently, as regulations on greenhouse gas emissions have become stricter, driven by global warming, there is increasing interest in engines utilizing environmentally friendly fuels. In this context, ammonia is attracting attention as a potential alternative to fossil fuels in the future. However, due to its distinct fuel properties compared to conventional fuels, research is being conducted on utilizing diesel as an ignition source for ammonia. In this study, the effects of diesel injector fuel flow rate, and micro-pilot (MP) diesel injection timing on combustion and exhaust emission characteristics were analyzed in a single cylinder 12L marine ammonia-diesel dual-fuel engine. Two types of diesel micro-pilot injectors were tested. The first one was high flow rate micro-pilot injector (HMPI) and the second one was low flow rate micro-pilot injector (LMPI). HMPI injector had 66% more number of fuel injector nozzle hole and 250% larger fuel flow rate. Therefore, HMPI injector could distribute diesel more widely within the combustion chamber in a short injection duration, which led to advantages such as an increased ratio of premixed combustion in diesel, improved oxygen utilization in the combustion cylinder, and enhanced ignitability of ammonia. To maintain a constant energy ratio between ammonia and diesel under steady engine load conditions, the injection durations were adjusted, and MP diesel injection timing was varied in increments of 5 crank angle degrees (CAD) to evaluate performance and emission characteristics. The experimental results showed that HMPI demonstrated higher thermal efficiency and lower unburned NH3 and N2O emission levels compared to LMPI. HMPI also showed improved overall performances under advanced MP diesel injection timing, however, performance of LMPI was also improved under the same conditions due to reduced interference between ammonia and MP diesel injection spray compared to the conditions under delayed MP diesel injection timing.
Jang, Ilpum, Park, Cheolwoong, Kim, Minki, Park, Chansoo, Kim, Yongrae, Park, Gyeongtae, Lee, Jeongwoo
Ammonia-Diesel Engines Segmented Modeling Approach and Simplified Combustion model Research2025-01-02326/16/2025
Ammonia-diesel dual-fuel engines can effectively reduce greenhouse gas (GHG) emissions. Aiming at the real-time control requirements of ammonia/diesel dual-fuel engines, this study proposes a segmented real-time modeling method and a heat release rate model simplification strategy by linearized heat release rate curves. First, the engine working cycle is divided into three parts: intake and exhaust stage, compression and expansion stage, and combustion process. Different simulation steps and modeling strategies are designed to optimize computational efficiency while maintaining the necessary level of accuracy at each stage. Secondly, based on the calibrated heat release rate (HRR) curves, feature points are extracted to construct a simplified linear heat release model. In the absence of calibration data, the characteristic points of the HRR curves are obtained through interpolation. Compared with the commonly used combustion model, the Wiebe model, the proposed simplified model can more easily obtain the parameters required for calibration while maintaining accuracy. Finally, the effectiveness of the model was verified experimentally under various cases. The results showed that the real-time modeling method can keep single-cycle simulation time in 2ms, the prediction deviations of the indicated mean effective pressure (IMEP) under 4% and the peak pressure in the cylinder (pmax) deviations are less than 2%, and the deviations of specific combustion angle (CA10, CA50, CA90) are controlled within 1°crankshaft angle (CA). It provides a model basis for the real-time control of ammonia diesel engines and is of great value in promoting the engineering application of ammonia fuel in transportation fields such as ship power systems.
Li, Guangyuan, Chen, Run, Wang, Xinran, Li, Tie, Zheng, Kexiong, Liu, Shaoling, Liu, Yanzhao, Lyu, Xiaodong
Experimental and Kinetic-Modeling Study of Ammonia/n-Heptane Combustion13-06-03-00204/9/2025
In recent years, researchers have increasingly focused on ammonia–diesel dual-fuel engines as a means of reducing CO2 emissions. Analyzing in-cylinder combustion processes is essential for optimizing the performance of ammonia–diesel dual-fuel engines. However, there is currently a lack of suitable reaction kinetics models for ammonia–diesel engine conditions. In this study, the ignition delay of ammonia/n-heptane mixtures was measured, and a reduced chemical mechanism was developed. Using rapid compression machine (RCM) experiments, the ignition delays of ammonia/n-heptane mixtures with different ammonia energy fractions (AEFs) (40%, 60%, and 80%) were measured. The test pressure ranged from 1.5 to 3.0 MPa, while the temperature ranged from 667 to 919 K, with an equivalence ratio of 1. The results showed that as the AEFs increased, the ignition delay of the premixed mixture also increased. When the AEF was 40%, the ammonia/n-heptane premixed mixture exhibited the negative temperature coefficient (NTC) phenomenon in the temperature range of 690 to 830 K. This phenomenon weakened as the AEF increased. Based on the experimental results, a reduced chemical mechanism for ammonia/n-heptane was developed, consisting of 162 species and 755 reactions. This model was able to accurately predict the ignition delay and laminar flame speed of ammonia/n-heptane mixtures, while reducing computational time by 94% compared to the detailed mechanism. When applied in three-dimensional simulations, this model effectively predicted the combustion and emission trends of ammonia–diesel engines. Advancing the first injection timing resulted in a decrease in NH3 concentration near the wall. The fuel injected during the first combustion injection increased the temperature near the wall, promoting the thermal decomposition of ammonia.
Cai, Kaiyuan, Liu, Yi, Chen, Qingchu, Qi, Yunliang, Li, Li, Wang, Zhi
Numerical Investigation of Fuel Injection Strategies for Ammonia-Diesel Dual-Fuel Engine2025-01-83684/1/2025
This study numerically investigates ammonia-diesel dual fuel combustion in a heavy-duty engine. Detailed and reduced reaction mechanisms are validated against experimental data to develop injection timing maps aimed at maximizing indicated thermal efficiency (ITE) while mitigating environmental impacts using stochastic reactor model (SRM). The equivalence ratio, ammonia energy share (AES), injection timing, and engine load are varied to optimize combustion efficiency and minimize emissions. The results demonstrate that advancing injection timing reduces ITE due to heightened in-cylinder temperatures, resulting in increased heat losses through walls and exhaust gases. Maximum chemical efficiency is observed at an equivalence ratio near 0.9 but decreases thereafter, influenced by ammonia’s narrow flammability range. Emission analysis highlights significant reductions in Global Warming Potential (GWP) and Eutrophication Potential (EP) with higher AES, driven by decreased CO2 and nitrogen oxides (NOx) emissions. Acidification Potential (ACP) initially rises with higher AES due to increased NOx production but diminishes as Pressure Rise Rate (PRR) and Ringing Intensity (RI) increase with higher AES and advancing injection timing. Conversely, Ozone Forming Potential (OFP) diminishes with higher AES due to reduced volatile organic compounds emissions.
Karenawar, Shivraj Anand, Yadav, Neeraj Kumar, Maurya, Rakesh Kumar
Combustion Characterization and Heat Release Rate Modeling of a Heavy-Duty Hydrogen-Diesel Dual-Fuel Engine2025-01-84184/1/2025
Introducing hydrogen (H2) into the intake air of diesel engines provides a near-term approach to reducing tailpipe CO2 emissions from heavy-duty commercial vehicles. The premixed hydrogen results in a complex H2-Diesel dual fuel (H2DF) combustion process, where H2 can both participate in the non-premixed diesel combustion and result in a propagating H2/air combustion. These interactions influence engine combustion characteristics, including in-cylinder pressure and heat release rate (HRR), as well as emissions. The nature and extent of the impact depends on the amount of H2 introduced as a function of the total fuel energy (H2 energy share ratio - HES), the trapped air mass, and engine operating conditions. To optimize the HES ratio under different conditions, it is crucial to understand how H2DF combustion differs from diesel combustion and how this limits engine operation and impacts emissions. To investigate these effects, a heavy-duty class 8 truck fitted with an H2DF system developed by Hydra Energy Corp. was tested on a chassis dynamometer. The engine was fitted with a suite of instrumentation, including in-cylinder pressure, air system pressure and temperature, exhaust flow rate, and emissions measurement equipment. Tests were conducted over three loads and speeds at fixed HES ratios, and detailed HES ratio studies were conducted at low- and mid-load cases at 1200 RPM. The results show that H2 introduction significantly impacts combustion characteristics and emissions, primarily influenced by the H2 equivalence ratio, with the engine control unit’s adjustments to boost pressure and diesel injection timing playing a critical role in combustion characteristics and engine-out emissions. At higher H2 equivalence ratios than 0.1, an H2/air premixed flame forms, advancing combustion phasing, which increases the maximum rate of pressure rise and reduces PM while raising NOx emissions. The Pcyl and HRR data are used to develop a semi-predictive combustion model imposing the net HRR profile using a multi-Wiebe function. A four-curve Wiebe function model can accurately capture the HRR and combustion characteristics across engine operating points, providing a reliable predictive tool at a given speed/load for various HES ratios. The developed understanding and combustion model provides valuable insight and techniques for future studies to further improve H2 utilization strategies tailored for the retrofit of heavy-duty H2DF truck applications.
Farzam, Reza, Guan, Mang, Gmoser, Raine, Steiche, Patrick, Kirchen, Patrick, McTaggart-Cowan, Gordon
Mixing-Controlled Combustion of Ethanol Enabled by Prechamber Ignition (PC-MCC): A Preliminary Experimental Demonstration04-18-02-00123/17/2025
This experimental study presents preliminary investigations of prechamber-enabled mixing-controlled combustion (PC-MCC) at −2 bar brake mean effective pressure (BMEP) and 2200 rpm with fuel-grade ethanol (E98). Experimental results are conducted on a prechamber retrofitted single-cylinder Caterpillar C9.3B test engine. First, a series of prechamber-only experiments were conducted with a motored engine to evaluate the salient combustion trends in response to relevant prechamber operating parameters. Under firing conditions, the prechamber operating strategy was assessed with respect to the impact on ignition assistance of direct-injected E98 and overall engine performance. The preliminary results indicate the jet-induced ignition process is robust and prompts diffusion combustion of E98 at diesel-like boundary conditions. The effect of external exhaust gas recirculation (EGR) on the residual tolerance of the prechamber combustion process was also investigated and showed stable combustion in both the main chamber and prechamber up to 30% EGR. Experiments were also conducted with the stock diesel engine for baseline comparison. At matched combustion phasing, mixing-controlled combustion of ethanol enabled by prechamber ignition was able to achieve heightened gross thermal efficiency while simultaneously reducing NOx and practically eliminating smoke emissions relative to diesel combustion. In addition, the covariance of load and standard deviation of combustion phasing was diesel-like and less than 2% and 1 CAD, respectively.
Zeman, Jared, Dempsey, Adam
Effect of Injection Pressure and Equivalent Ratio on Combustion and Emissions of The Ammonia/Diesel Dual Fuel Engine2025-01-71111/31/2025
In the context of low-carbon and zero-carbon development strategies, the transformation and upgrading of the energy structure is an inevitable trend. As a renewable fuel, ammonia has a high energy density. When ammonia is burned alone, the combustion speed is slow. The emissions of nitrogen oxides and unburned ammonia is high. Therefore, a suitable high-reactivity combustion aid fuel is required to improve the combustion characteristics of ammonia. Based on this background, this study converted a six-cylinder engine into a single-cylinder ammonia/diesel dual-fuel system, with diesel fuel as the base and a certain percentage of ammonia blended in. The impact of varying the injection pressure and equivalence ratio on engine combustion and emissions was examined. The results demonstrate that an appropriate increase in injection pressure can promote fuel-gas mixing and increase the indicated thermal efficiency (ITE). With regard to emissions, an increase in injection pressure has been observed to reduce unburned ammonia emissions and the equivalent greenhouse gases. An increase in the equivalence ratio results in the suppression of combustion within the engine cylinder, accompanied by a reduction in the peak of pressure curve and a delay in the phase corresponding to the peak. An increase in the equivalence ratio results in a longer ignition delay time and combustion duration. Indicated thermal efficiency and ammonia combustion efficiency show a tendency to increase first and then decrease. With regard to emissions, the combustion process is adversely affected by an increase in the equivalence ratio. It leads to an increase in total hydrocarbon and CO emissions. Unburned ammonia decreases. NOx emissions increase first and then decreases influenced by cylinder temperature.
Wang, Hu, Lv, Zhijie, Zhang, Shouzhen, Wang, Mingda, Yang, Rui, Yao, Mingfa
Study on Injection Parameters of Ammonia/Diesel Dual Direct Injection Low-Speed Engine2025-01-71141/31/2025
With the adoption of the IMO Greenhouse Gas Emission Reduction Strategy Revision, the international shipping industry is facing huge pressure to reduce greenhouse gas emissions, and the conversion of ship power from traditional fossil fuels to low-carbon and zero-carbon fuels is the fundamental solution, and ammonia fuel, as a zero-carbon fuel, is an important direction for the development of ship power in the future. Based on a marine low-speed diesel engine with a bore of 520 mm, computational fluid dynamics (CFD) numerical simulation was carried out to study the effects of different diesel energy fractions, ammonia injection pressure, ammonia injection timing and ammonia diesel injection interval on the combustion and emission characteristics of the engine under the dual-fuel combustion mode of high-pressure dual direct injection. The calculation results show that under the condition of the current engine, 5% of diesel energy can reduce carbon emissions by 92.8% under the premise of successful ignition. Increasing the injection pressure of ammonia fuel results in more effective work, greater turbulent kinetic energy, better mixing effect of ammonia fuel and diesel flame, and reduces unburned ammonia and greenhouse gas emissions, but there is a trade-off between high NOx or high N2O emissions. Diesel ammonia 2CA injection in advance can take into account various emission data well, and is the most suitable injection interval.
Yang, Jincheng, Liu, Long, Gui, Yong
Development of an Algorithm for Identifying Fuel Blending Ratios for Methanol/Gasoline Flex-Fuel Engines2025-01-71071/31/2025
Flex-fuel vehicles play a crucial role in energy conservation and emission reduction; however, they often rely on expensive fuel identification sensors at the nozzle to accurately control the blending ratio. To reduce costs and enhance engine flexibility, this paper presents a flexible fuel proportion identification algorithm that utilizes exhaust oxygen content measured by the oxygen sensor and engine air intake data. Additionally, the algorithm incorporates air intake feedback control and λ feedback control, which adjusts both the throttle opening and fuel mass of the flex-fuel engine, ensuring optimal operating conditions at all times. A methanol-gasoline flex-fuel engine model was developed using GT-Power, and the algorithm model was implemented in Simulink software. Then, a co-simulation model of GT-Power and Simulink is established. In the GT-Power engine model, three parameters—engine speed, load, and methanol blending ratio—are set for the sweep points. The algorithm model in Simulink calculates the methanol blending ratio based on the data output from the GT-Power sweep points. Finally, the calculated blending ratio is compared with the actual blending ratio set in GT-Power to verify the accuracy of the algorithm described in this paper. Results indicate that the error in the methanol blending ratio calculated by the algorithm is less than 2%. The algorithm presented in this paper utilizes real-time simulation technology based on fully algebraic equations, resulting in high efficiency, accuracy, and sensitivity.
Qian, Pengfei, Nan, Tiantian, Luo, Weixing, Du, Yang, Wang, Long, Chen, Zhanming
Experimental Study on the Effects of Ammonia Energy Substitution Rate on Combustion and Emission Performance in a Hydrogen Engine2025-01-71051/31/2025
To advance the application of zero-carbon ammonia fuel, this paper presents an experimental investigation on the potential of ammonia substitution using a 2.0L ammonia-hydrogen engine, where ammonia is injected into the intake port and hydrogen is directly injected into the cylinder. The study examines the effects of ammonia substitution rate under various load conditions on engine combustion and emission performance. Results indicate that the maximum ammonia energy substitution rate reached 98%, and within the stable combustion boundary, the mass fraction of unburned ammonia was less than 3%. The ammonia energy substitution ratio increased with load, and ammonia addition significantly suppressed pre-ignition and knocking. As ammonia content increased, ignition timing advanced, combustion duration extended, ignition delay prolonged, COV increased, peak cylinder pressure, and pressure rise rate decreased, with a corresponding decrease in peak heat release rate. Compared to a pure hydrogen engine, the ammonia-hydrogen dual-fuel engine significantly improved brake thermal efficiency (BTE), which continued to rise with increasing ammonia energy substitution rate. At BMEP = 0.8 MPa, BTE reached a maximum of 41.1%. With increased ammonia addition, unburned NH3 emissions in the exhaust gradually increased, while NOx emissions decreased overall, but N2O emissions showed an increasing trend.
Wu, Weilong, Xie, Fangxi, Chen, Hong, Du, Jiakun, Li, Yong
Techno-Economic Analysis of the Implementation of a Dual-Fuel ENGINE for Agricultural Applications2024-36-004412/20/2024
The growing demand for decarbonization and reduction of emissions from internal combustion engines used in the agricultural sector is mainly responsible for the utilization of alternative or low-carbon fuels. In this context, in situ biogas production and Dual-fuel technology bring an important opportunity for farmers to use gas with diesel or biodiesel in the agricultural machinery, reducing production costs and carbon emissions. To this end, this work evaluates efficiency, emissions, and economic performance in an internal combustion engine equipped with a Dual-fuel injection for diesel and methane. The tests were carried out on a four-cylinder turbocharged Agrale tractor, model BX6110, with modifications for run on diesel-NGV blends under operating conditions with engine speed from 1500 to 2150 rpm, fuel injection times of 80 to 200, at full load. The results showed that the diesel flow was constant during the tests, therefore, power increases depending on the NGV injected. Maximum power, lower specific fuel consumption and highest economic performance through Dual-fuel technology were reached with an injection time of 200. Reducing in CO2 emissions with short injection times is observed.
Rincon, Alvaro Ferney Algarra, Alvarez, Carlos Eduardo Castilla, Filho, Aldir Carpes Marques, Oliveira Faria, Rafael, Volpato, Carlos Eduardo Silva, Oliveira Notório Ribeiro, Jéssica
Efficient Estimation of Laminar Flame Speed in Dual-Fuel SI Engines: A Simplified Methodology for 1-D Predictive Combustion Simulation2024-36-018412/20/2024
The increasing impacts of the greenhouse effect have driven the need to reduce pollutant emissions from internal combustion engines. Renewable fuels are promising alternatives for emission reduction, and enhancing engine efficiency can further decrease specific emissions. This study explores the development of dual-fuel engines to meet these goals, focusing on dual-fuel combustion in spark-ignition (SI) engines using two different bioethanol and natural gas mixtures. A novel methodology for 1-D predictive combustion simulation in dual-fuel SI engines was developed and implemented in GT-Suite software. The approach involves a straightforward estimation of the laminar flame speed of the fuel mixture and the calibration of turbulent combustion parameters using a genetic optimization algorithm, without the need for complex chemical kinetics models. The results indicate that the proposed methodology can reproduce combustion characteristics, achieving satisfactory outcomes across most tested conditions. In the light of emerged findings, the research serves as a further baseline for future research activities dealing with dual fuel combustion in internal combustion engines.
Pasa, Giovanni Duarte, Martins, Clarissa, Cota, Filipe, Dornelles, Henrique, Duarte, Thales, Rosalen, Rodrigo, Pujatti, Fabrício José Pacheco
Combustion of Hydrated Ethanol and Gasoline RON95 Ultra-High Pressure Direct Injection in Optical Access SI Engine2024-36-015212/20/2024
High and ultra-high pressure direct injection (UHPDI) can enhance efficiency gains with flex-fuel engines operating on ethanol, gasoline, or their mixtures. This application aims to increase the engine’s compression ratio (CR), which uses low CR for gasoline due to the knocking phenomenon. This type of technology, involving injection pressures above 1000 bar, permits late fuel injection during the compression phase, preventing auto-ignition and allowing for higher compression ratios. UHPDI generates a highly turbulent spray with significant momentum, improving air-fuel mix preparation, and combustion, resulting in even greater benefits while minimizing particulate matter emissions. This study aims to develop ultra-high-pressure injection systems using gasoline RON95 and hydrated ethanol in a single-cylinder engine with optical access. Experimental tests will be conducted in an optically accessible spark ignition research engine, employing thermodynamic, optical, and emission results. In the present work, the spark plug was placed in the lateral, so the ignition and part of the flame propagate close to the cylinder wall, and it will exchange with greater heat to the wall than the flame portions that propagate towards the central region of the chamber. Therefore, the flame front propagates at different speeds; causing stretching and wrinkling that can lead to instabilities and cyclic variability. To address this issue, this work presents experimental results that, through the images post-processing of flames under a SOI (start of injection) sweep strategy in the compression phase to closer of the spark ignition, associating the non-uniform propagation velocity of the flame with the cyclic variability. The fuel impingement on the wall was critical in this scenario, which led to higher soot concentrations and diffusive flames for gasoline. It was found that the injection close to the spark plug enhances the heat release, and combustion stability, decreasing soot emissions. Total unburned hydrocarbons (THC), Nitrous oxides (NOx), aldehydes, and soot emissions decreased for end of injection events closer to the spark ignition. This trend opposes the increase observed in CO emissions.
Malheiro de Oliveira, Enrico R., Mendoza, Alexander Penaranda, Martelli, Andre Luiz, Dias, Fábio J., Weissinger, Frederico F., dos Santos, Leila Ribeiro, Lacava, Pedro Teixeira
Performance and Emissions of a Hydrogen Dual-Fuel Engine Using Diesel and HVO as Pilot Fuels2024-01-428611/5/2024
A comprehensive experimental study of hydrogen–diesel dual-fuel and hydrogen-hydrotreated vegetable oil (HVO) dual-fuel operations was conducted in a single-cylinder diesel engine (bore 85.0 mm, stroke 96.9 mm, and compression ratio 14.3) equipped with a common rail fuel injection system and a supercharger. The hydrogen flow rate was manipulated by varying the hydrogen excess air ratio from 2.5 to 4.0 in 0.5 increments. Hydrogen was introduced into the intake pipe using a gas injector. Diesel fuel and HVO were injected as pilot fuels at a fixed injection pressure of 80 MPa. The quantity of pilot fuel was set to 3, 6, and 13 mm3/cycle. The intake and exhaust pressures were set in the range of 100–220 kPa in 20 kPa increments. The engine was operated at a constant speed of 1,800 rpm under all conditions. The pilot injection timing was varied such that the ignition timing was constant at the TDC under all conditions. The results demonstrated that smoke was lower when HVO was used as the pilot fuel than when diesel fuel was used, and that knocking occurred at lower excess air ratios of hydrogen when diesel fuel was used as the pilot fuel than when HVO was used. This is owing to the longer ignition delay of diesel fuel compared to that of HVO. The wider distribution of diesel fuel compared to that of HVO accelerates the chemical reactions in the premixed mixture, leading to autoignition. In addition, misfiring occurred when diesel fuel was used under low boost pressure operating conditions. This was attributed to differences in the ignition properties of the pilot fuel. These results demonstrate that HVO can be operated over a wider load range and at a wider hydrogen excess air ratio than diesel fuel operation.
Mukhtar, Ghazian Amin, Tange, Kota, Nakatani, Satoshi, Horibe, Naoto, Kawanabe, Hiroshi, Morita, Gin, Hiraoka, Kenji, Koda, Kazuyuki
Study of H 2 and NH 3 Mixtures in a Gasoline-Fueled Engine2024-01-428811/5/2024
The combustion of hydrogen (H2) as a fuel is attractive due to its zero-carbon nature and combustion-enhancing properties when used to supplement other fuels. However, the challenge of using H2 as a fuel for transportation applications is the difficulty of onboard storage. One solution to this is to crack onboard stored ammonia (NH3) into H2 which can be supplied to the combustion chamber. However, the reforming process is not always 100 % efficient which can lead to the presence of NH3 in the combustion process. The presence of NH3 can influence engine performance, combustion and emissions. Therefore, this experimental study reports the differences in engine performance between H2 and NH3 reformate mixtures (H2/NH3/N2) added to gasoline in a dual-fuel engine setup under both stoichiometric (λ=1.0) and lean-burn (λ>1.0) operating conditions in a spark ignition (SI) engine. In this study, gasoline was used as the main fuel, with the H2 and NH3 reformate blends studied having energy substitution ratios ranging from 0% to 23%. The results showed that the use of H2 and NH3/H2/N2 mixtures reduced carbon-based emissions. However, there was an increase in nitrogen-based emissions compared to gasoline with increased H2 and NH3 content.
Yavuz, Mustafa, Wu, Mengda, Cova-Bonillo, Alexis, Brinklow, George, Herreros, Jose, Tsolakis, Athanasios
Premixed Dual-Fuel Combustion of Camelina sativa Oil and Ethanol03-18-01-00018/6/2024
Dual-fuel (DF) engines enable efficient utilization of a low reactivity fuel (LRF), usually port-injected, and a high reactivity fuel (HRF) provided directly into the cylinder. Ethanol and Camelina sativa oil can be ecologically effective but not fully recognized alternatives for energy production using modern CI engines equipped with a common rail system and adopted for dual fueling. The high efficiency of the process depends on the organization of the combustion. The article describes the premixed dual-fuel combustion (PDFC) realized by dividing the Camelina sativa dose and adjusting its injection timing to the energetic share of ethanol in the DF mixture. The injection strategy of HRF is crucial to confine knock, which limits DF engine operation, but the influence of EGR is also important. The research AVL engine’s dual-fueling tests focused on combustion process modification by the proposed injection strategy and cooled EGR at different substitution rates. For all examined points of the engine run, the volumetric heat release rate diagrams, cylinder pressure, and temperature illustrate changes that resulted from the tested fueling options. Additionally, engine thermal efficiency and emissions are presented. Because of potential application, the tests were confined to one engine speed (n = 1500 rpm). The research confirmed the possibility of efficiently applying raw Camelina sativa oil as an HRF for DF engines and ethanol (LRF) under high-load conditions.
Pawlak, Grzegorz, Skrzek, Tomasz, Kosiuczenko, Krzysztof, Płochocki, Patryk, Simiński, Przemysław
TOC99-06-03-0TOC6/21/2024
TOC
Tobolski, Sue
Experimental and Numerical Investigations of a Dual-Fuel Hydrogen–Kerosene Engine for Sustainable General Aviation2024-01-60016/17/2024
Reducing CO2 emissions is an increasingly important issue. In aviation, approaches such as e-propulsion only represent a solution for special applications due to the low energy density of batteries. Because of the low-cost and robust design of combustion engines, this concept is still the most suitable for general aviation. For defossilization, besides e-fuels and bio-fuels, which represent the so-called sustainable aviation fuels (SAF), hydrogen can serve as a promising energy carrier for CO2 reduction. For this purpose, the combustion process of a dual-fuel hydrogen–kerosene (Jet A-1) engine was developed and investigated for use in small aircrafts. This study explores the influence of hydrogen addition on combustion parameters, emissions, and efficiency. An advantage of this special design as dual-fuel engine (hydrogen and kerosene) is the possibility of redundancy operation in the event of a H2 fuel system failure as well as full operational capability of the aircraft in the event of hydrogen supply difficulties at various airports. Besides test bench investigations, 3D CFD simulations were performed to optimize hydrogen injector position, ensure backfire-free operation, and improve mixture formation. In addition to a low load and high load point, a high-altitude point was investigated based on real flight data. The maximum achievable hydrogen energy shares, limited by abnormal combustion, and the respective CO2 reductions are shown. Furthermore, the influence of the hydrogen mass distribution in the inlet ports was investigated to achieve an advantage in the homogenization of the hydrogen–air mixture. Finally, the efficiency losses in hydrogen dual-fuel mode compared to base kerosene operation are shown in a detailed analysis.
Reitmayr, Christian, Wiesmann, Frederik, Gotthard, Thomas, Hofmann, Peter
Influence of Intake Charge Temperature and EGR Rate on the Combustion and Emission Characteristics of Ammonia/Diesel Dual-Fuel Engine2024-37-00256/12/2024
Ammonia has emerged as a promising carbon-free alternative fuel for internal combustion engines (ICE), particularly in large-bore engine applications. However, integrating ammonia into conventional engines presents challenges, prompting the exploration of innovative combustion strategies like dual-fuel combustion. Nitrous oxide (N2O) emissions have emerged as a significant obstacle to the widespread adoption of ammonia in ICE. Various studies suggest that combining exhaust gas recirculation (EGR) with adjustments in inlet temperature and diesel injection timing can effectively mitigate nitrogen oxides (NOx) emissions across diverse operating conditions in dual-fuel diesel engines. This study conducts a numerical investigation into the impact of varying inlet charge temperatures (330K, 360K, and 390K) and EGR rates (0%, 10%, and 20%) on the combustion and emission characteristics of an ammonia/diesel dual-fuel engine operating under high-load conditions, while considering different shares of ammonia energy. Computational fluid dynamics (CFD) simulations are executed using Converge software. Subsequently, multi-linear regression models are developed, utilizing ammonia share, inlet charge temperature, and EGR rate as independent variables, and emission parameters as dependent variables. The best-fitted regression model can be employed to analyze the response surface of performance parameters. The optimal CO2 reduction, approximately 30%, is observed under the conditions of (390K, 40% NH3, and EGR20), as indicated by the results. Furthermore, under the conditions of (360K, 20% NH3, and EGR20), the findings indicate a notable reduction of NO2, approximately 65% compared to diesel. Additionally, the findings suggest that NH3 reduction peaks at higher temperatures, with approximately a 50% decrease observed.
Hoseinpour, Marziyeh, Karami, Rahim, Salahi, Mohammad Mahdi, Mahmoudzadeh Andwari, Amin, Gharehghani, Ayat, Garcia, Antonio
Potential Analysis of Defossilized Operation of a Heavy-Duty Dual-Fuel Engine Utilizing Dimethyl Carbonate/Methyl Formate as Primary and Poly Oxymethylene Dimethyl Ether as Pilot Fuel03-17-07-00534/18/2024
This study demonstrates the defossilized operation of a heavy-duty port-fuel-injected dual-fuel engine and highlights its potential benefits with minimal retrofitting effort. The investigation focuses on the optical characterization of the in-cylinder processes, ranging from mixture formation, ignition, and combustion, on a fully optically accessible single-cylinder research engine. The article revisits selected operating conditions in a thermodynamic configuration combined with Fourier transform infrared spectroscopy. One approach is to quickly diminish fossil fuel use by retrofitting present engines with decarbonized or defossilized alternatives. As both fuels are oxygenated, a considerable change in the overall ignition limits, air–fuel equivalence ratio, burning rate, and resistance against undesired pre-ignition or knocking is expected, with dire need of characterization. Two simultaneous high-speed recording channels granted cycle-resolved access to the natural flame luminosity, which was recorded in red/green/blue and OH chemiluminescence. Selected conditions were investigated in more detail with the simultaneous application of planar laser-induced fluorescence of OH and HCHO and recording natural flame luminescence in a cycle-averaged manner. Poly oxymethylene dimethyl ether was used as pilot fuel, building on prior investigations. The mixture of 65 vol% Dimethyl Carbonate and 35 vol% Methyl Formate with prior verification on a passenger-car-sized engine substitutes synthetic natural gas in this study. Thermodynamically, the increased compression ratio up to 17.6 resulted in feasible operation and increased indicated efficiency. On the lower compression ratio of 15.48, a more comprehensive range of applicable air–fuel equivalence ratios and increased degrees of freedom regarding the pilot’s total energy share are observed compared to the base configuration with natural gas and EN590 as pilot fuel. The air–fuel equivalence ratio sweep from λ = 1.0–2.0 revealed predominantly premixed and high-temperature heat release via OH*. The temporal and spatial evolution shifts while leaning out the mixture with increasing gradients on the radial distribution and decouples for lean mixtures from the initial spray trajectory.
Mühlthaler, Markus Sebastian, Härtl, Martin, Jaensch, Malte
Comparison of Tabulated and Complex Chemistry Approaches for Ammonia–Diesel Dual-Fuel Combustion Simulation03-17-07-00554/18/2024
Using ammonia as a carbon-free fuel is a promising way to reduce greenhouse gas emissions in the maritime sector. Due to the challenging fuel properties, like high autoignition temperature, high latent heat of vaporization, and low laminar flame speeds, a dual-fuel combustion process is the most promising way to use ammonia as a fuel in medium-speed engines. Currently, many experimental investigations regarding premixed and diffusive combustion are carried out. A numerical approach has been employed to simulate the complex dual-fuel combustion process to better understand the influences on the diffusive combustion of ammonia ignited by a diesel pilot. The simulation results are validated based on optical investigations conducted in a rapid compression–expansion machine (RCEM). The present work compares a tabulated chemistry simulation approach to complex chemistry-based simulations. The investigations evaluate the accuracy of both modeling approaches and point out the limitations and weaknesses of the tabulated chemistry approach. When using two fuels, the tabulated chemistry approach cannot reproduce misfiring events due to inherent model limitations. By adjusting the model parameters of the tabulated chemistry model, it is possible to reproduce experimental results accurately for a specific case. However, using the adjusted parameters for simulations with changed injection timing or interaction angle between the sprays shows that no predictive calculations are possible. The parameter set is only valid for a single operation point. Further simulations show that the complex chemistry approach can capture the complex interaction between both directly injected fuels for different operation points. It correctly predicts the ignition as well as heat release. Therefore, the approach allows predictive combustion simulations. Furthermore, it reproduces the occurrence of misfiring in cases of unsuitable interaction of both sprays and injection timing.
Krnac, Dominik, Manickam, Bhuvaneswaran, Holand, Peter, Pathak, Utkarsh, Scharl, Valentin, Sattelmayer, Thomas
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
Computational Investigation of Hydrogen-Air Mixing in a Large-Bore Locomotive Dual Fuel Engine2024-01-26944/9/2024
The internal combustion engine (ICE) has long dominated the heavy-duty sector by using liquid fossil fuels such as diesel but global commitments by countries and OEMs to reduce lifecycle carbon dioxide (CO2) emissions has garnered interest in alternative fuels like hydrogen. Hydrogen is a unique gaseous fuel that contains zero carbon atoms and has desired thermodynamic properties of high energy density per unit mass and high flame speeds. However, there are challenges related to its adoption to the heavy-duty sector as a drop-in fuel replacement for compression ignition (CI) diesel combustion given its high autoignition resistance. To overcome this fundamental barrier, engine manufacturers are exploring dual fuel combustion engines by substituting a fraction of the diesel fuel with hydrogen which enables fuel flexibility when there is no infrastructure and retrofittability to existing platforms. This work studies the implications of mixing port-injected hydrogen fuel in a large-bore rail engine operating with hydrogen-diesel dual fuel combustion. Previous work was done to validate a single-cylinder computational model to data collected on this engine when operating with dual fuel combustion of natural gas and diesel. This model was then modified to employ gaseous hydrogen as the port injected fuel. First, a grid sensitivity study was performed, and it was concluded that the computational mesh was refined enough to minimize numerical error. Modeling implications are then investigated by comparing two RANS turbulence models in terms of their prediction of turbulent mixing predictions of hydrogen and air. It was seen that both had minimal differences in bulk mass flow trends, but choice of RANS turbulence model could impact qualitative predictions of fuel-air stratification. Lastly, hydrogen injection timing and flow rate were varied, and it was concluded that the highest injection flow rate is best for both premixing hydrogen with air and reducing hydrogen mass left in the intake. Additionally, given the potential limitations of hydrogen injection pressure, injection timing can be advanced to allow more time for mixing when injection velocity is maximized.
O'Donnell, Patrick, Kazmouz, Samuel, Wu, Sicong, Ameen, Muhsin, Klingbeil, Adam, Lavertu, Thomas, Jayakar, Vijayaselvan, Sheth, Pushkar, Wijeyakulasuriya, Sameera
A Study on Combustion and Emission Characteristics of an Ammonia-Biodiesel Dual-Fuel Engine2024-01-23694/9/2024
Internal combustion engines, as the dominant power source in the transportation sector and the primary contributor to carbon emissions, face both significant challenges and opportunities in the context of achieving carbon neutral goal. Biofuels, such as biodiesel produced from biomass, and zero-carbon fuel ammonia, can serve as alternative fuels for achieving cleaner combustion in internal combustion engines. The dual-fuel combustion of ammonia-biodiesel not only effectively reduces carbon emissions but also exhibits promising combustion performance, offering a favorable avenue for future applications. However, challenges arise in the form of unburned ammonia (NH3) and N2O emissions. This study, based on a ammonia-biodiesel duel-fuel engine modified from a heavy-duty diesel engine, delves into the impact of adjustments in the two-stage injection strategy on the combustion and emission characteristics. The research findings indicate that as the pre-injection timing advances, the ignition delay increases, and the first-stage heat release is delayed, the indicated thermal efficiency initially increases and then decreases, reaching a maximum of 48.5%, surpassing the indicated thermal efficiency of pure biodiesel combustion. With the advancement of the pre-injection timing, nitrogen oxides (NOx) emissions exhibit an overall declining trend, while nitrous oxide (N2O), total hydrocarbons (THC), and carbon monoxide (CO) emissions increase, and there is an optimal pre-injection timing for reducing unburned ammonia emissions. Adjusting the main-injection timing can modulate the phase of ammonia-biodiesel combustion to improve the indiated thermal efficiency. Compared to the pure biodiesel mode, the equivalence CO2 emissions from the ammonia-biodiesel mode are significantly reduced by approximately 40%. Furthermore, this study compares the combustion and emission performance of ammonia-biodiesel and ammonia-diesel combustion modes, revealing that using biodiesel for ammonia ignition results in better performance, with reduced unburned ammonia emissions and higher indicated thermal efficiency. This research offers guidance for optimizing ammonia-biodiesel dual-fuel engine combustion and provides a pathway for further energy efficiency and carbon reduction in internal combustion engines.
Liu, Yi, Cai, Kaiyuan, Qingchu, Chen, Yunliang, Qi, Wang, Zhi
Numerical Investigation on Hydrogen Enrichment and EGR on In-Cylinder Soot and NOx Formation in Dual-Fuel CI-Engine2024-01-20984/9/2024
To mitigate the NOx emissions from diesel engines, the adoption of exhaust gas recirculation (EGR) has gained widespread acceptance as a technology. Employing EGR has the drawback of elevating soot emissions. Using hydrogen-enriched air with EGR in a diesel engine (dual-fuel operation), offers the potential to decrease in-cylinder soot formation while simultaneously reducing NOx emissions. The present study numerically investigates the effect of hydrogen energy share and engine load on the formation and emission of soot and NOx from hydrogen-diesel dual-fuel engines. The numerical investigation uses an n-heptane/H2 reduced reaction mechanism with a two-step soot model in ANSYS FORTE. A reduced n-heptane reaction mechanism is integrated with a hydrogen reaction mechanism using CHEMKIN to enhance the accuracy of predicting dual-fuel combustion in a hydrogen dual-fuel engine. The results show that hydrogen enrichment plays a significant role by decreasing the soot precursor concentration by increasing the hydroxyl (OH) radical and suppressing soot formation by enhancing oxidation. Hydrogen enrichment in dual-fuel operation significantly reduces soot and NOx emissions under low load conditions. Adding hydrogen in diesel engines decreases the concentration of acetylene (C2H2), locally inside the combustion chamber, which inhibits soot formation. The findings highlight the synergistic benefits of combining hydrogen and EGR in a dual-fuel engine, offering a viable strategy for achieving lower NOx levels without compromising on soot emissions. This research contributes to the advancement of cleaner and more efficient propulsion technologies, especially in the context of heavy-duty applications where stringent emissions standards are a critical concern.
Yadav, Neeraj Kumar, Maurya, Rakesh Kumar
Experimental Investigation of Internal and External EGR Effects on a CNG-OME Dual-Fuel Engine2024-01-23614/9/2024
Dual-fuel engines powered by renewable fuels provide a potential solution for reducing the carbon footprint and emissions of transportation, contributing to the goal of achieving sustainable mobility. The investigation presented in the following uses a dual-fuel engine concept running on biogas (referred to as CNG in this paper) and the e-fuel polyoxymethylene dimethyl ether (OME). The current study focuses on the effects of exhaust gas rebreathing and external exhaust gas recirculation (EGR) on emissions and brake thermal efficiency (BTE). A four-cylinder heavy-duty engine converted to dual-fuel operation was used to conduct the engine tests at a load point of 1600 min-1 and 9.8 bar brake mean effective pressure (BMEP). The respective shares of high reactivity fuel (HRF, here: OME) and low reactivity fuel (LRF, here: CNG) were varied, as were the external and internal EGR rates and their combinations. CNG was injected into the intake manifold to create a homogeneous air-fuel mixture, while OME was introduced as a pilot injection directly into the combustion chamber. Results showed an increase in total hydrocarbons (THC) and carbon monoxide (CO) emissions, while nitric oxide (NOx) emissions were significantly reduced compared to diesel operation. Soot emissions were completely mitigated due to the absence of direct carbon bonds in both CNG and OME. For the initial stage of the study, exhaust gas rebreathing was implemented on only one exhaust valve through a second event lift. For the second part of the study, the second event lift was also installed on the other exhaust valve. At a substitution rate of 50 % CNG, THC emissions could be lowered by up to 35 %, CO emissions by up to 50 % and NOx emissions by up to 18 % with the use of internal EGR. The combination of internal and external EGR reduced emissions even further.
Jost, Ann-Kathrin, Guenthner, Michael, Weigel, Alexander
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