Browse Topic: Natural gas

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On Natural Gas Combustion Split into Diesel Like Architecture of a Compression Ignition Engine Retrofitted for Spark Ignition Operation2026-37-00296/9/2026
In commercial areas that no longer favor diesel engines, such as Europe, it might be interesting to convert an existing compression ignition engine to the spark ignition operation and to use natural gas (NG) because of its advantages: availability of still abundant supplies worldwide and environmental benefits compared to conventional liquid fossil fuels. This paper first presents experimental results on NG combustion inside such a converted engine with diesel-like architecture dedicated to light-duty vehicles and passenger cars. Particularly, our study carried out at the engine test bed revealed that in certain operating points (low speed and load, stoichiometric mixture and rather high spark advance), the combustion is split into two distinct events (first, a fast combustion inside the cylinder and piston bowl and then, a slower combustion occurring outside the bowl-in combustion chamber, in other words, in the squish region), which is not specific to the standard spark ignition engine. This is clearly illustrated by a rate of heat release profile with two peaks. The explanations for such combustion event are also supported by a 3D CFD study showing the in-cylinder NG distribution. The combination of experimental and numerical investigations contributes to the understanding of NG combustion in the diesel like architecture of the converted CI engine when subjected to deliberately extreme conditions, namely non-optimal spark advance setting exceeding the maximum brake torque spark advance.
Clenci, Adrian F., Popa, Robert, Berquez, Julien, Iorga-Siman, Victor, Magheru, Catalin, Punov, Plamen, Niculescu, Rodica
Comparative Toxicological Assessment of Exhaust Emissions from Modern Low-Emission Passenger Vehicles2026-37-00056/9/2026
As vehicle technologies evolve toward electrification and advanced aftertreatment, understanding the biological implications of their exhaust emissions remains essential. This study presents a harmonized comparative toxicological assessment of five Euro 6 vehicles representing gasoline, hybrid, plug-in hybrid, compressed natural gas (CNG), and diesel technologies. Vehicles were tested under realistic driving conditions on a chassis dynamometer. Diluted exhaust was delivered directly to human lung epithelial cells (A549) using a controlled air–liquid interface (ALI) exposure system. Solid and total particle number emissions were measured, and deposited particle mass was estimated from size-resolved distributions and deposition efficiency. Vehicles equipped with particulate filtration showed lower solid particle emissions overall, while differences between gasoline particulate filter-equipped vehicles indicated that hybridization can further influence emission levels. Diesel operation during active diesel particulate filter (DPF) regeneration produced more than two orders of magnitude higher particle number emissions compared to normal operation. When expressed as deposited mass, vehicle ranking differed from number-based emissions, highlighting that emission metrics do not directly translate into delivered biological dose. Exposure to whole exhaust consistently induced stronger cytotoxic and inflammatory responses than to gaseous phase alone. Membrane integrity disruption and IL-1β release showed clear particle-associated amplification, with the strongest effects observed during diesel DPF regeneration. These findings demonstrate persistent technology-dependent differences in particle emissions and acute biological responses among modern low-emission vehicles.
Tsakonas, Georgios, Stamatiou, Rodopi, Lazou, Antigone, Samaras, Zissis, Elihn, Karine
Experimental Investigation of Diesel, Aqueous Ammonia, and Compressed Natural Gas Mixtures on Performance and Emissions in a Compression Ignition Engine04-19-03-00115/30/2026
Abstract This study investigates and evaluates systematically the combustion, performance, and emissions characteristics of heavy-duty diesel engines fueled by diesel–ammonia–compressed natural gas triple blends. While dual-fuel systems are well-documented, the interactive effects of ammonia and CNG within a single compression ignition (CI) engine remain largely unexplored. Experiments were conducted on a 300 Nm, 660 rpm diesel engine by testing pure diesel, diesel–ammonia blends (10–20 wt.% aqueous ammonia), and triple-fuel mixtures containing 10% of the total energy from compressed natural gas. Pure diesel was first tested to provide baseline data, and subsequently blends were tested for a comparative study. The primary contribution of this work is the identification of a synergistic effect of the fuel triple blends on engine performance and emissions. Results indicate that all fuel blends improve thermal efficiency and reduce fuel consumption compared to conventional diesel. The blend containing 20% aqueous ammonia, 80% diesel, and 10% of the total fuel energy supplied by compressed natural gas achieved the highest thermal efficiency of 39.7% (7% higher than diesel) and the lowest brake specific fuel consumption of 211.22 g/kWh. Furthermore, emissions analysis revealed that carbon dioxide and nitrogen oxide emissions were significantly reduced with this triple blend. The blend decreased carbon dioxide by 26.6% and nitrogen oxide emissions by 32.1%, while hydrocarbon emissions were also lowered by up to 29.2%. Carbon monoxide emissions increased slightly for the triple blends, reaching a maximum value of 3.9028 g/kWh for the A20D80CNG10 mixture, compared to diesel operation. The slight increase in carbon monoxide emissions for triple blends highlights a trade-off in emission behavior. These findings address the combined utilization of diesel–ammonia–compressed natural gas triple-fuel mixtures in heavy-duty engines, demonstrating that strategic blending can simultaneously improve efficiency while mitigating environmental impact. Graphical Abstract
Sinkala, Happy, Sarıtaş, Mehmet, Kül, Volkan Sabri, Akansu, Selahaddin Orhan, Ünalan, Sebahattin
Risk Assessment of Bunkering Process for LNG River Powered Ship2026-99-17225/22/2026
At present, with the rapid development of LNG powered ships, China’s LNG powered ships have formed a certain scale, but the speed of infrastructure construction such as bunkering stations restricts the development of LNG powered ships. In this process, “tank truck-to-ship bunkering”(TTS) has become one of the most widely used bunkering methods in China because of its flexible, fast and convenient characteristics, but there are many hidden dangers in the bunkering process. According to the characteristics of TTS, fault tree method is used to identify the risk of bunkering process, and the leakage of pipeline system is listed as the basic risk factor. The leakage probability of different aperture is analyzed by industry statistics. Three different leakage scenarios are selected and the consequences are simulated by PHAST software. The study shows that the failure of the valve and flange can easily lead to the leakage of LNG in the TTS process, and the leakage of the medium aperture and the full aperture will form the liquid pool, so some measures should be taken for the protection.
Dong, Yuanchao
Combustion Enhancement via Discharge Current Modulation under Turbulence Conditions2026-01-03364/7/2026
Utilizing low carbon fuel in lean burn combustion presents a compelling strategy for improving thermal efficiency and reducing NOx emissions. Methane, the main content of natural gas, still receives challenge of a rapid and complete combustion process because of its low flame speed. The long combustion duration deteriorates the performance of a spark ignition engine, in terms of poor combustion instability and misfire. Although ignition timing can be utilized to adjust the combustion phasing, the ignition process faces challenges due to reduced background pressure and temperature at advanced spark timings. In this paper, a rapid compression machine equipped with a specially designed flow chamber is utilized to enhance the turbulence flow, and a custom-built ignition module is utilized to provide boosted discharge current to enhance the ignition stability under flow conditions. An effective spark energy required to enhance the combustion process is investigated under both stoichiometric and lean conditions. Further increase of discharge current amplitude beyond this boundary yields minimal impact on the flame propagation process. This study will offer important insights for developing an on-demand ignition energy profiling strategy to reduce sparkplug electrode erosion.
Jin, Long, Cong, Binghao, Yu, Xiao, Kong, Xiangxin, Reader, Graham, Zheng, Ming
Effect of Passive Pre-Chamber Geometry on Performance and Emissions of a Single-Cylinder Natural Gas Large Bore Engine2026-01-03334/7/2026
The maritime industry is one of the most energy-intensive sectors, characterized by high fuel consumption and significant environmental impact. As global trade relies on shipping, the challenge of reducing pollutants and greenhouse gas emissions becomes ever more pressing. Natural gas (NG) is considered as a transitional fuel, capable of lowering CO₂ emissions by 20–30% compared to conventional marine fuels. However, to fully harness this potential, significant advances in combustion technology are necessary, particularly with ultra-lean combustion strategies. One of the most promising pathways is pre-chamber combustion, a solution that can simultaneously improve the efficiency and sustainability of NG marine engines. In this scenario, the passive pre-chamber geometry plays a key role, as it directly influences ignition behavior, combustion stability, and exhaust emissions. This work presents an experimental study conducted on a single-cylinder marine engine prototype, retrofitted from a diesel baseline, and equipped alternatively with four passive pre-chambers featuring different geometrical configurations. The tests were conducted at an engine speed of 1500 rpm and different loads to evaluate the influence of pre-chamber geometry on engine performance and exhaust emissions. Key parameters such as combustion phasing, efficiency, and pollutant formation were analyzed and compared between the four setups. Results showed that pre-chamber design affects the interaction between the turbulent jets and the main chamber mixture, leading to significant variations in both combustion efficiency and emission trends. These findings provide new insights into the role of passive pre-chamber geometry in optimizing large-bore NG marine engines, offering a valuable contribution to the development of cleaner and more efficient propulsion systems for the maritime sector.
Marchitto, Luca, Tornatore, Cinzia, Pennino, Vincenzo, Mariani PhD, Antonio, Beatrice, Carlo, Accurso, Francesco, Gorietti, Valentina, Pesce, Francesco, Giardino, Angelo, Vitti, Luciano
BEV Incremental CO 2 Emissions in a Ranked Order Electric Grid2026-01-04244/7/2026
Battery Electric Vehicles (BEV) have been sold as ‘Zero Emissions Vehicles’ (ZEV) by governments to reduce transportation CO2. While they are not ZEV because they run on grid electricity, they could be ‘effectively ZEV’ if the incremental CO2 is ‘very small’. At the national level, this is estimated using following metrics: (1) Internal Combustion Engine Vehicle (ICEV) fuel consumption, from the total US gasoline consumption divided by the total fleet miles driven, 25 mpg or 350 g CO2/mi, (2) Strong Hybrid Electric Vehicles (HEV) about one third less, 240 g CO2/mi. (3) BEV energy consumption, using data from systematic on-road testing of a wide range of vehicles, estimated at 40 kWh/100 mi for a US sales mix. (4) Electricity marginal CO2: in a ranked order grid, zero-CO2 sources are prioritized and supplemented by fossil sources. IEA hourly data show that the US 48 contiguous states are self-contained, with zero-CO2 sources providing a third of total demand. The response to hourly demand changes comes largely from natural gas and coal power stations, with EPA data showing a combined marginal CO2 of 600 g CO2/kWh. On replacing an ICEV by a BEV, the reduction in gasoline use, - 350 g CO2/mi, is offset to two thirds by higher electricity consumption, 40 x 600 / 100 = + 240 g CO2/mi. BEV marginal CO2 is therefore similar to HEV, and not ‘much smaller’ than ICEV. This is because HEV engines and fossil power stations have similar efficiency and similar fuel CO2 intensity.
Phlips, Patrick
Experimental Evaluation of After-Treatment Solutions for Heavy-Duty Natural Gas Vehicles to Meet Future CNVII Regulations2026-01-03764/7/2026
The heavy-duty truck market in China has seen a significant increase in the adoption of natural gas-powered engines over the past two years. Simultaneously, the anticipated release of the China VII emissions regulation proposal by the end of 2025 is expected to impose stricter emissions limits on all heavy-duty engines, including new particulate number (PN10) thresholds analogous to those in the Euro 7 regulation. While tailpipe oxides of nitrogen (NOx) and methane (CH4) emissions from natural gas engines can be mitigated through tighter lambda control and adjustments to catalyst volume and precious metal (PGM) loading, addressing NOx and particulate number (PN) emissions necessitate more advanced after-treatment solutions. Although natural gas combustion is virtually soot-free, the entrainment of lubricating oil into the combustion chamber, especially during cold-start conditions, poses a challenge, leading to potential exceedance of the proposed future China VII limits. Additionally, PN emissions from natural gas vehicles are highly dependent on duty-cycles and the state of the actual engine, with applications involving frequent stop/go operation experiencing increased piston ring wear, and thus, higher oil consumption, and elevated PN emissions. This study aimed to evaluate the performance of different after-treatment solutions for natural gas engines in meeting future China VII emissions standards, with a particular focus on the efficacy of particle filters for controlling PN10 emissions. Three different after-treatment configurations, comprising close-coupled and underfloor three-way catalysts, as well as bare and coated filters, were tested on a 15L China VI commercial natural gas engine in a controlled laboratory environment. Emissions and PN10 data were collected over regulatory cold and hot World Harmonized Transient Cycle (WHTC) test cycles, and analyzed for light-off behavior, conversion efficiencies, system pressure drop, and filtration effectiveness for particles as small as 10nm. The relative advantages and challenges of each configuration are discussed. The results indicate that natural gas engines will likely require the integration of particle filter devices to comply with future China VII PN10 limits. The results also show that NOx compliance is challenging and fine-tuning of the lambda calibration is essential for CNVII.
Gao, Jiahui, Besch, Marc, Ding, Ning, He, Suhao, Zhao, Yuxin, Yixiao, Li, Shen, Ye
Reactivity Controlled Compression Ignition (RCCI) Combustion Engine Characteristics Fuelled with Diesel/Compressed Natural Gas (CNG) and Diesel/Methanol Fuel Pairs2026-01-03194/7/2026
Ultra-low oxides of nitrogen (NOx) and particulate matter (PM) from reactivity-controlled compression ignition (RCCI) combustion have motivated researchers to explore more about low temperature combustion (LTC) engines. In this study, a comparative analysis of combustion, performance, and emission characteristics of RCCI combustion fuelled with diesel/compressed natural gas (CNG) and methanol/diesel fuel pairs has been carried out with respect to baseline compression ignition (CI) combustion. All experiments were performed in a constant speed engine at four different engine loads. For RCCI combustion experiments, a constant premixed ratio (rp= 0.50) and 15% exhaust gas recirculation (EGR) were used. The results exhibited a significant reduction in NOx emissions and relatively smoother RCCI combustion compared to baseline CI combustion. RCCI mode combustion resulted in relatively superior engine performance compared to baseline CI combustion, especially at higher engine loads. A comparison between the RCCI combustion fuelled with gaseous fuel (CNG) as a low reactivity fuel (LRF) and a liquid fuel (methanol) showed a slightly lower brake thermal efficiency (BTE) of CNG/diesel fuelled RCCI combustion compared to methanol/diesel fuelled RCCI combustion at low loads. As the load increased, the trend of BTE was reversed. The combustion characteristics of CNG/diesel fuelled RCCI combustion were found to be more stable compared to methanol/diesel fuelled RCCI combustion. The NOx emissions were lowest in methanol/diesel fuelled RCCI irrespective of engine load. At low load, methanol/diesel fuelled RCCI suffered from higher hydrocarbon (HC) and carbon monoxide (CO) emissions, while CNG/diesel fuelled RCCI maintained relatively lower HC and CO emissions.
Saikia, Bhargav, Kant, Akshay, Gupta, Abhishek, Singh, Akhilendra Pratap
Experimental and Kinetic Modeling Study of Aged Natural Gas Three-Way Catalyst Performance2026-01-03734/7/2026
The applicability of three-way catalyst (TWC) models for system-level aftertreatment simulations under transient operating conditions of natural gas engines depend on accurate integration of reaction kinetics as a function of the air-fuel equivalence ratio lambda(λ). A comprehensive global kinetic model has been developed for an aged commercial three-way catalyst (TWC), incorporating key reaction pathways including oxidation of CO, CH₄, C₂H₆, and H₂; reforming of CH₄ and C₂H₆; the water-gas shift reaction; and NO reduction via CO and H₂. The model also accounts for oxygen storage capacity (OSC) and its dynamic interaction with CO and H₂. To calibrate kinetic parameters, systematic bench-scale flow reactor experiments were conducted under lean, stoichiometric, and rich conditions. Performance metrics focused on CH₄ and C₂H₆ oxidation and reforming across varying O₂ and CO concentrations, and NO reduction with CO and H₂ under different oxygen levels. Experimental results revealed that CO suppresses the reforming of CH₄ and C₂H₆. NO conversion was observed between 150°C and 600°C, with H₂-driven reduction producing NH₃, N₂, and N₂O depending on lambda (λ). Under rich conditions, complete NO conversion occurred from 150°C, while lean conditions showed reduced NO conversion at elevated temperatures due to H₂ oxidation. NO reduction with CO initiated at 250°C, achieving full conversion under rich conditions. The model accurately captures the influence of λ on NO reduction with both H₂ and CO, predicts NH₃ formation under rich conditions, and simulates H₂ generation via the water-gas shift reaction above 400°C. It successfully reproduces λ sweep data (λ = 0.95–1.02) and demonstrates CO inhibition effects on H₂ oxidation and NO reduction. This global model is validated with dithering reactor data and qualitatively captures key trends in data which aids in catalyst sizing, calibration robustness and the system level modeling of end of useful life parts. Further validation of the current developed model with lean-rich cycle tests confirms the model’s ability to predict NOx slip at the onset of rich cycles impacting the ability to accurately predict NOx emissions during engine braking events in system level models.
Raj, Richa, Kim, Mi-Young, Aigbiremolen, Grace, Srinivasan, Anand
Impact of Hydrogen on Methane and Pollutant Emissions over Three-Way Catalysts with Natural Gas–Hydrogen Blends2026-01-03574/7/2026
Blending natural gas (NG) with hydrogen (H₂) can improve combustion and engine performance while potentially facilitating the catalytic conversion of methane and other pollutants, resulting in cleaner tailpipe emissions. This study evaluates the impact of H2 on the conversion of methane, CO, and NOx emissions on a commercial three-way catalyst (TWC) in a flow reactor using synthetic gas mixtures that simulate stoichiometric engine exhausts with NG or NG+H₂ combustion. The work examines whether, and how, the additional amount of H₂ in the exhaust stream affects the conversion efficiency of methane and other pollutants. Experiments were conducted with both degreened and aged catalysts under controlled conditions, systematically varying temperature, the air-to-fuel equivalence ratio (λ), and λ modulation. Test conditions covered λ values from 0.996 to 1.000 to represent nominally stoichiometric engine operation with different λ modulation amplitudes, as well as a range of temperatures to inform control strategies for effective CH₄, CO, and NOₓ reduction. Overall, the results show that hydrogen addition significantly improves the conversion efficiency of CH₄ and NOₓ, particularly at temperatures below 500 °C. More significantly, this study highlights that exhaust gas composition, operating temperature, λ management, and the oxygen storage capacity of the TWC all play major roles in affecting the tailpipe emissions from NG and NG+H₂ combustion.
Prikhodko, Vitaly, Wang, Min, Park, Yeonshil, Chen, Hai-Ying, Pihl, Josh
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
Potential of a Hydrogen Fuel-Share Combustion Concept for a Conventional Medium-Speed Marine Diesel Engine2026-01-50072/2/2026
To meet the International Maritime Organization’s (IMO) short-term greenhouse gas (GHG) reduction targets, partial decarbonization of the existing fleet, often powered by medium-speed diesel engines, is required. One approach for reducing CO2 emissions is to enrich the charge air with hydrogen to substitute diesel. However, hydrogen’s high reactivity can lead to combustion abnormalities such as backfire, pre-ignition, and knocking, thus limiting the feasible admixture rates. These challenges are particularly relevant in medium-speed diesel engines designed for high power output and efficiency at low rpm. While hydrogen fuel-share has previously been tested in small-bore engines at moderate loads, this study investigates the influence on combustion and achievable hydrogen admixture rates in a medium-speed, 4-stroke diesel engine operating with up to 30 bar net indicated mean effective pressure (net IMEP). To minimize retrofitting efforts and to preserve diesel performance, the investigations were conducted on a single-cylinder engine with representative design features of a conventional diesel engine: a high compression ratio, Miller valve timing, valve overlap, and a piston with deep valve pockets. The piston ring system is suited for heavy fuel oil (HFO) operation. Hydrogen was supplied via a port fuel injection (PFI) system. 0D/1D process simulations supplement the experimental data. Findings indicate that energetic hydrogen admixture rates of up to 43% are achievable at low loads, limited by an advancing start of combustion, and up to 15% hydrogen share at high loads, constrained by backfire. This results in an average CO2 reduction of ~22% on the E2 cycle for constant-speed main propulsion engines. Due to rising NOx emissions, the results are only applicable when meeting IMO Tier II limits with selective catalytic reduction (SCR). The results demonstrate that conventional medium-speed diesel engines are suited for hydrogen fuel-share operation and that CO2 reductions comparable to liquid natural gas (LNG) conversions are feasible.
Achenbach, Tobias, Meinert, Robert, Mahler, Kay, Kunkel, Christian, Rösler, Sebastian, Prager, Maximilian, Jaensch, Malte
Comparative Journey Towards Sustainable Energy: CNG and Bio-Diesel Fuels in India2026-26-01161/16/2026
India being highly populated and developing country, the demand for various alternative fuel is increasing drastically. It is driven by the need to reduce dependency on traditional fossil fuels & reduce impact on environmental issues like Greenhouse gas, emissions & pollution. The potential options, CNG (Compressed Natural Gas) & Biodiesel, are becoming increasingly popular and important. Biodiesel, a renewable fuel which is produced from waste materials & crops which grown repeatedly & easily available while CNG is more sustainable than diesel as natural gas is a cleaner-burning fossil fuel in comparison to coal or oil. This paper will focus on comparison between basic properties of Diesel, CNG & Biodiesel. In this study will also focus on survey of various Government initiatives, policies & infrastructural development which are evolving to encourage the usage of CNG & Biodiesel. These fuels are emerging as promising alternative contenders to traditional diesel. It has the potential to reduce carbon footprints, making them environment friendly & more sustainable energy options. This survey also summaries the industry motivation from govt initiatives to promote the aim of cleaner transportation & its transition towards future sustainable energy. This study presents a comparative journey of CNG & Biodiesel in India. Key parameters like fuel properties, feedstocks and its availability, storage and handling, product integration, emissions and endurance performance assessments, customer acceptability etc. are considered for understanding these fuels in a better way. Also, it will highlight the key bottlenecks, technical challenges & the obstacles hindering the widespread adoption of Biodiesel as compared to CNG. The paper also elaborates the challenges on sustainability of biodiesel and CNG fuels and the futuristic opportunities in carbon neutral fuels like H2. The paper concludes with the comparative study of CNG & Biodiesel on various aspects from ideation to execution.
Bondada, Nandita, Baruah, Labanya, Mokhadkar, Rahul
Solving the Exhaust Valve CNG Wear Problem: An Investigation into Hard-Facing Material Deposition for CNG Exhaust Valves2026-26-02781/16/2026
Compressed Natural Gas (CNG) offers a compelling alternative fuel solution due to its lower carbon emissions and cost-effectiveness compared to conventional gasoline. However, the dry combustion characteristics of CNG, coupled with higher combustion temperatures, often accelerate Exhaust valve face and Exhaust seat insert wear in internal combustion engines. Intake valve face and Intake seat insert are exposed to fresh air charge and temperature during engine operation remain with in limit and no issue reported in Intake valve side. This study addresses the critical challenge of premature exhaust valve wear in CNG applications by investigating the root cause and implementing improvements in the exhaust valve facing material, aiming to enhance durability and reliability for widespread CNG vehicle adoption. Exhaust valve face in CNG engine subjected to extreme condition leads to excessive valve face wear and cracking. To address these challenges, various technologies like hard material deposition, hardening processes, and Diamond-Like Carbon (DLC) coatings have been developed for valve face wear resistance improvement. Most common solution adapted by different OEM are using Hard facing material to resist wear and crack. Hard facing material is deposited by welding process which itself is overly critical and need precise control to achieve desired part quality. Our development focused on identifying key process-controlled parameters for preventing valve seat wear in Exhaust Valve by optimizing hard facing material deposition process parameters, hard facing material microstructure, residual stress, blowholes, and hardness.
Poonia, Sanjay, Kumar, Chandan, Kundu, Soumen, Kumar, Prabhakar, Vats, Rajesh, Khan, Prasenjit, Sharma, Shailender
Combustion Dynamics and Performance Optimisation Using Higher HCNG Blends for Decarbonising the Gas Genset Sector2026-26-02511/16/2026
Air pollution is profligate becoming a serious worldwide problem with the increasing population and its subsequent demands. Diesel, Gasoline, Natural Gas, Propane, etc., are some of the traditional fuels used in the power generation sectors. Diesel fuel, popularly utilized for backup power in critical operations, is valued for its swift activation time. This makes diesel generators a preferred choice for commercial properties and hospitals requiring reliable emergency power. Moreover, natural gas, distributed through local utility grids, provides a convenient and readily available fuel source for generators, eliminating the need for on-site fuel storage. On the other hand, CPCB has instructed to modify the emission regulations for genset engines for decarbonization and development clean fuel. The change from CPCB II to CPCB IV+ standard shows the commitment of the Indian government towards environmental sustainability and COP26. Pondering to the stringent emission norms, researchers are exploring various alternate fuels. This has resulted in increased usage of hydrogen as fuel for Internal Combustion Engines (ICE). Leapfrog to hydrogen ICE will take time for the technology and infrastructure to mature, therefore Hydrogen enriched Compressed natural gas (HCNG) is an intermediate solution for de-carbonisation of ICE. HCNG blends take benefit of the unique combustion properties of hydrogen and at the same time reduce the demand for pure hydrogen. HCNG can take advantage of existing investment in natural gas infrastructure and also has much higher volumetric energy storage density than pure hydrogen. In this study, an in-use multi-cylinder NG operated CPCB II compliant Genset engine was assessed with various HCNG fuel blends. The main objective of the study was to analysis the combustion dynamics and to evaluate the effect of 25HCNG and 30HCNG on the genset engine without major modification in Hardware. The study also draws focus on the combustion parameter variations with higher HCNG blend induction in the engine. With the usage of HCNG the CO, HC pollutants reduce by around 26-46% keeping similar trend of NOx. This approach can make HCNG a probable candidate to reduce emissions from genset engines.
Bandyopadhyay, Debjyoti, Sutar, Prasanna S, Dhar, Rit Prasad, Sonawane, Shailesh Balkrishna, Rairikar, Sandeep D, Thipse, Sukrut S, Singh, Sauhard, Mishra, Sumit Kumar, Bera, Tapan, Badhe, Rajesh, Tule, Shubham, Aghav, Yogesh, Lakshminarasimhan, Krishna
Correlation of Particulate Matter Species on Gasoline Direct Injection (GDI) Vehicle with Ethanol Blended Gasoline: Real Drive Emissions based Portable Emission Measurement System2026-26-02161/16/2026
On the way to net zero emissions and to cut the oil import bills, NITI Aayog, Government of India and Ministry of Petroleum & Natural Gas (MoP&NG) has rolled out roadmap for ethanol blending in India during 2020-2025. Also, National Policy on Biofuels – 2018, provides an indicative target of 20% ethanol blending under the Ethanol Blended Petrol (EBP) Programme by 2030. Considering these Government’s initiatives current studies were performed on BSVI compliant gasoline direct injection vehicle on RDE compliant route (Route formulated by Indian Oil R&D Centre) with different ethanol blended gasoline fuel formulations i.e., E0 (Neat Gasoline), E10 (10% Ethanol in gasoline) & E20 (20% Ethanol in gasoline). The study aims to determine the compliance of Conformity Factor (C.F.) for ethanol blended gasoline fuel on Direct Injection gasoline engine. The conformity factors were calculated in each case for CO, NOx & PN using moving window average evaluation method. For reference CO2 characteristics curve, CO2 values were measured over Modified Indian Driving Cycle (MIDC) on chassis dynamometer. The study suggests that the use of oxygenated fuel formulations (E10 & E20) impacts tail pipe emissions in a greater way and without any change in the hardware of after treatment devices of the vehicle tail pipe emissions can be reduced. Paper presents RDE as well laboratory mass emissions data collected. However, all the emission values are well below the typical BSVI/Euro6d limits and the C.F for NOx is also below than stated limit of BS_2.0 IRDE (Indian Real Driving Emissions).
Kant, Chander, Arora, Ajay, Saroj, Shyamsher, Kumar, Prashant, Sithananthan, M, Chakradhar, Dr Maya, Kalita, Mrinmoy
Misfires Detection in Bi-Fuel Engines – A Brief Note2026-26-01201/16/2026
With the expansion of compressed natural gas (CNG) filling station in India, bi-fuel vehicles are gaining popularity in recent times. Bi-fuel engine runs on more than one fuel, say in both CNG and petrol. Hence, the engine must be optimized in both the fuel modes for performance and emissions. However, due to the inherent differences in combustion characteristics: ignition dynamics and fuel properties, they pose a significant challenge in case of detection of misfires. Misfires are caused because of faulty injection systems and ignition systems and incorrect fuel mixture. Accurate detection is essential as misfires deteriorate the catalysts performance and may impacts emission. Misfires (or engine roughness) is calculated from engine crankshaft speed signal. In this study, the effectiveness of crankshaft-based misfires detection method, comparison of misfire signals magnitude in bi-fuel modes and practices developed for accurate detection of misfires is presented.
Thiyagarajan, Abhinav, N, Gobalakrishnan, R, Hema
Development of High BMEP Natural Gas Engine with Knock Mitigation2026-26-01211/16/2026
The stringent emission norms over the past few years have driven the need to use low-carbon fuels and after treatment technology. Natural gas is a suitable alternative to diesel heavy-duty engines for power generation and transportation sectors. Stoichiometric combustion offers the advantages of complete combustion and low carbon dioxide emissions. Turbocharging and cooled exhaust gas recirculation (EGR) technology enhances the power density along with reduced exhaust emissions. However, there are several constraints in the operation of natural gas spark ignition engine such as exhaust gas temperature limit of 780 °C, sufficient before turbine pressure for EGR drivability, boost pressure, peak cylinder pressure limit and knocking. These limits coulld restrict the engine BMEP (brake mean effective pressure). In the present study, tests were conducted on a V12, 24 liters, heavy duty natural gas fuelled spark ignition engine (600 HP) with different EGR and turbocharger configurations to achieve 16 bar BMEP without abnormal combustion. Considering the maximum exhaust temperature limit of 780 °C of exhaust system, minimal engine hardware changes were done to ensure less complexity, cost-effective engine development with robust design. The turbine trim was decreased from 89% to 84% to avoid excessive high before turbine backpressure, backflow of residual gases into cylinder and knock possibility. EGR system optimization with mixer enhanced EGR mixing and distribution in all cylinders that improved BSFC by 3%. During knock calibration, the offset to base ignition timing was used for individual cylinders to mitigate knock. Endurance trial of 100 hours was carried out to validate the reliability of engine design and calibration, and no issues were detected. The developed engine is the highest BMEP V12 engine in its segment in India using stoichiometric combustion with cooled EGR and three-way catalyst. The engine is certified with latest Indian CPCB IV+ emissions norms.
Khaladkar, Omkar, Marwaha, Akshey
Experimental Evaluation of Energy and Exergy of Hydrogen, CNG and Gasoline Fuelled High-Speed Spark Ignition Engine2026-26-02581/16/2026
The maximum power is recorded with Gasoline than CNG and Hydrogen fuel. The maximum exergy and energy efficiency is with Hydrogen, followed by CNG and then Gasoline. Hydrogen fuel has a maximum potential to convert into energy. The maximum energy destruction of 48.7kW for gasoline fuel at 3000 rpm and followed by CNG and hydrogen. The maximum entropy generation of 85.5 W/K with Gasoline and 60.72 W/K and 29.39W/K for CNG and hydrogen engine respectively at 10000 rpm. The entropy generation rate increase with engine speed. The highest rate of heat release is from hydrogen fuel, followed by Gasoline and CNG.
Shinde, Apurwa Balasaheb, Kadam, Tushar, karunamurthy, K, SHINDE, DR BALU
Failure Prevention of Permanent Deformation in HNBR Elastomeric Diaphragms Used in CNG Valve Applications2026-26-02941/16/2026
Hydrogenated nitrile butadiene rubbers (HNBR) and their derivatives have gained significant importance in automotive compressed natural gas (CNG) valve applications. In one of the four-wheelers, CNG valve application, HNBR elastomeric diaphragms are being used for their excellent sealing and pressure regulation properties. The HNBR elastomeric diaphragm was developed to sustain CNG higher pressure However, it was found permanently deformed under lower pressures. In this research work, number of experiments was carried out to find out the primary root cause of diaphragm permanent deformation and to prevent the failure for safe usage of the CNG gas. HNBR diaphragm deformation investigation was carried out using advanced qualitative and quantitative analysis methods such as Soxhlet Extraction Column, Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Optical Microscopy (OM), Scanning Electron Microscopy (SEM), and Thermogravimetric Analysis (TGA). For this purpose, we have carried out experiments on OK (HNBR diaphragm with higher bar pressure) and field-failed diaphragms (HNBR diaphragm deformed after lower bar CNG pressure). We have found that OK and Field failed diaphragms have different filler concentrations and uneven dispersion and distribution. Also, the crosslinking density of the failed Field diaphragms was observed in declining order in comparison with the OK diaphragms. TGA and SEM analysis revealed the filler concentration and morphology of the diaphragms. The chemical nature and thermal properties have been analysed using FTIR and DSC analysis techniques. The Soxhlation extractions study helped to understand the crosslinking density of OK and field failure diaphragms. Preventive measures have been implemented to mitigate the HNBR diaphragm permanent deformation issue.
Patil, Bhushan Gulab, NAIKWADI, AMOL, Mali, Manoj, Tata, Srikanth
Design Solutions for Ice-Induced CNG Filling Failures- Field Issue Resolution through Filter Geometry and Seal Material Reengineering2026-26-05151/16/2026
This study investigates the phenomenon of receptacle icing during Compressed Natural Gas (CNG) refueling at filling stations, attributing the issue to excessive moisture content in the gas. The research examines the underlying causes, including the Joule-Thomson effect, filter geometries, and their collective impact on flow interruptions. A comprehensive test methodology is proposed to simulate real-world conditions, evaluating various filter types, seal materials and moisture levels to understand their influence on icing and flow cessation. The findings aim to offer ideas for reducing icing problems. This will improve the reliability and safety of CNG refueling systems.
Virmani, Nishant, Sawant, Shivraj Madhukar, C R, Abhijith
A Comparative Analysis of Passenger Car Fuel Economy between Laboratory and Real Driving Testing2026-26-02251/16/2026
In India, fuel economy is one of the most critical factors influencing a customer's decision to own a passenger car. Beyond consumer preference, fuel consumption also plays a significant role in the nation's energy security. In line with this, the government promotes fuel-efficient vehicles and technologies through various regulations, policies, and mandates. Vehicle manufacturers, in response, focus on designing vehicles that align with both customer expectations and regulatory requirements. Fuel economy certification is typically based on standardized laboratory tests that simulate controlled environmental conditions, driving cycle (MIDC), vehicle load, and operation of electrical and electronic systems. However, actual on-road driving conditions by end user vary significantly due to factors such as traffic conditions, ambient temperature, air conditioning use, driving behavior and variable loading of the vehicle. With implementation of Bharat Stage VI, Real Driving Emission (RDE) became mandatory from April 2023 to meet the requirements of conformity factors (CF) for NOX and PN emission. RDE regulation scope doesn’t include measurement or compliance for fuel economy during real driving condition. For the purpose of this study, laboratory and real driving emissions (RDE) testing were carried out in accordance with AIS 137 Part 3. For systematic comparison, fuel economy was calculated after modifying Carbon Balance equation in line to CAFÉ regulation S.O. 1072 (E) Dated 23rd April 2015. This study presents a comparative analysis of fuel economy results obtained from the testing different vehicles operating on different fuels like Gasoline, Diesel and Bi-fuel (Compressed Natural Gas (CNG) + Gasoline). The paper concludes with finding of study as impact of real-world driving conditions, particularly of ambient temperature and real driving on fuel efficiency of passenger cars.
Singh, Abhay Pratap, Bathina, Revanth Kumar, Tijare, Shantanu
Thermal Shock Test Rig for CNG Shut-Off Valve2026-26-05261/16/2026
In Automobile, Gasoline Engines are being used along with electrically operated shut-off valve installed at the roof of bus in case of higher capacity of CNG systems. In order to start/ stop CNG supply from cylinder for running of engine/ safety/ servicing an electrical operated ignition switch/ key controlled CNG Shut-Off Valve is placed just after the cylinders. There have been few failures of these CNG shut-off valves in field application. On investigation, it was observed that the CNG shut-off valve gets failed due to water ingress in coils from the cracks on surface generated due to spray of water (due to daily washing of bus and rain) on heated shut-off valves. In order to validate this field failure and subsequent validation of modified design, a need was felt to use a test rig which can exactly simulate the water spray based thermal shocks. However, there was no low cost facility available to simulate the field service condition for validation. Therefore, a low cost test set-up was designed and developed to simulate the failure in test lab to analyze the failure and root cause analysis and further durability validation of improved design. The designed and developed test rig was very useful to investigate the root cause of failures and validation of improved samples. The test rig has been in operation for 2 years without any failures and has validated more than 30 samples of existing and improved samples. The test rig was designed and developed completely in-house and is a low cost in price as well as low running cost.
Srivastava, Pravin Kumar, Vivekanand, Vivekanand, Kumar, Satish
Early Prediction of CNG Filling Time Using Artificial Intelligence for Design Optimization2026-26-06621/16/2026
Over the past few decades, Compressed Natural Gas (CNG) has gained popularity as an alternative fuel due to its lower operating cost compared to gasoline and diesel, for both passenger and commercial vehicles. In addition, it is considered more environmentally friendly and safer than traditional fossil fuels. Natural gas's density (0.7–0.9 kg/m3) is substantially less than that of gasoline (715–780 kg/m3) and diesel (849–959 kg/m3) at standard temperature and pressure. Consequently, CNG needs more storage space. To compensate for its low natural density, CNG is compressed and stored at high pressures (usually 200-250 bar) in on-board cylinders. This results in an effective fuel density of 180 kg/m3 at 200 bar and 215 kg/m3 at 250 bar. This compression allows more fuel to be stored, extending the vehicle's operating range per fill and minimising the need for refuelling. Natural Gas Vehicles (NGVs), particularly those in the commercial sector like buses and lorries, need numerous CNG cylinders in order to maximise vehicle range on a single fill. However, increasing the number of on-board cylinders results in a proportional increase in refuelling time, which can have a detrimental impact on operational costs for commercial fleet owners. The CNG fuel system, which usually consists of large-volume petrol cylinders (up to 800 litres), is an essential part of vehicle development. A quick petrol fill-up time is ideal because these vehicles must frequently refuel because they frequently travel vast miles each day. At the moment, the refuelling time is calculated by evaluating the CNG filling time following prototype development. Design modifications to the fuel system are necessary if the filling time is too long, which results in severe time and cost penalties as well as delays in the development cycle of new vehicle products. A mathematical model based on a number of influencing factors has been created by combining AI and ML technology. At the initial Zero design release gateway, this model will forecast the time needed to fill up with CNG petrol on all commercial vehicle platforms. This early prediction will enable additional optimization to improve gas filling time. The goal of this research work is to optimize the filling time for various platform before physical vehicle builds.
Choudhary, Aditya Kant, Petale, Mahendra, Dutta, Surabhi, Bagul, Mithilesh
For CNG and FFV Fuel Application Exhaust Valve Redesign and Robustness Improvement to Combat Abnormal Valve Guide and Seat Wear2026-26-01251/16/2026
Today, passenger car makers around the world are striving to meet the increasing demand for fuel economy, high performance, and silent engines. Corporate Average Fuel Economy (CAFE) regulations implemented in India to improve the fuel efficiency of a manufacturer's fleet of vehicles. CAFE goal is to reduce fuel consumption and, by extension, the emissions that contribute to climate change. CNG (Compressed Natural Gas) engines offer several advantages that help manufacturers meet and exceed these standards. The demand for CNG vehicles has surged exponentially in recent years, CNG engine better Fuel efficiency and advantage in CAFÉ norms make good case for OEM & Customer to use more CNG vehicle. CNG is dry fuel compared to gasoline. These dry fuels lack lubricating properties, unlike conventional fuels like petrol, diesel and biofuels, which are wet and liquid. Consequently, the operations and failures associated with these fuels differ. The materials and designs of engine parts, such as fuel lines, ECU, exhaust valves, and cylinder heads, vary depending on the fuel used. In CNG engine most challenging issue is leakage at Valve seat and Valve face interface causing unstable combustion and power drop. This study discusses the countermeasures adopted to address the high valve face, Valve guide and valve seat wear in cylinder heads and engine valves. The investigation focuses on material, design, and manufacturing process improvements specially for Exhaust valve, supported by part-level and vehicle-level validation and testing for CNG exhaust valves and cylinder heads.
Poonia, Sanjay, Kumar, Chandan, Sharma, Shailender, Khan, Prasenjit, Bhat, Anoop, P, Prasath, Neb, Ashish
Development of a CNG-Diesel Dual Fuel Tractor with Mechanical Fuel Injection System2026-26-01141/16/2026
Identification of renewable and sustainable energy solutions remains a key focus area for the engine designers of the modern world. An avenue of research and development is being vastly dedicated to propelling engines using alternate fuels. The chemistry of these alternate fuels is in general much simpler than fossil fuels, like diesel and gasoline. One such promising and easily available alternate fuel is compressed natural gas (CNG). In this work, a 3-cylinder, 3-liter naturally aspirated air-cooled diesel engine from the off-highway tractor application is converted into a CNG Diesel Dual fuel (CNG-DDF) engine. Part throttle performance test shows the higher NMHC and CO emissions in CNG-DDF mode which have been controlled by an oxidation catalyst in C1 8-mode emission test. A comparative performance shows that the thermal efficiency is up to 2% lower with CNG-DDF with respect to diesel. However, it has shown the benefit of 44% in Particulate Matter, while retaining the same NOx + NMHC levels as the baseline diesel engine. The cycle average CO emission has been found to increase by 6%. Average exhaust gas temperature has been found to be lower by up-to 54°C with CNG-DDF. To control the particulate and HC levels of the baseline NA engine, the CNG injection has been confined from 20% to 85% engine loads, across all engine speeds. The peak firing pressure and in-cylinder temperature are lower by ~3% and ~7%, and the SoC got retarded by max 4°CA with CNG-DDF which is in-agreement with drop in thermal efficiency. The outcome from the engine dyno level testing has been successfully validated through the tractor testing.
Choudhary, Vasu, Mukherjee, Nalini, Kumar, Sanjeev, Tripathi, Ayush, Nene, Devendra
Combustion Chamber Geometry Comparison in Natural Gas Engines under Conventional and Dethrottled Operation2025-36-021712/18/2025
Growing interest in cleaner energy has spurred progress in engine technology, focusing on greater efficiency and lower emissions. Methane-based fuels, like compressed natural gas (CNG), have become an alternative for spark-ignition engines, especially in Brazil. Among performance strategies, dethrottled operation stands out by reducing intake restrictions and minimizing pumping losses, a major inefficiency in conventional spark ignition engines. This improves thermal efficiency and reduces both fuel consumption and emissions. This study experimentally examines the performance and combustion of a CNG-powered Hyundai HR 2.5 16V engine, converted from diesel to spark ignition with natural gas, comparing factory (omega) and custom (reentrant) piston geometries under both conventional and dethrottled modes. The research evaluates how piston design affects combustion stability, efficiency, and emissions across different load strategies. Tests were conducted at 7, 8, and 9 bar loads, as well as full load, with engine speed at 1800 rpm. In conventional mode, load was controlled by the throttle at stoichiometric conditions (λ = 1); in dethrottled mode, the throttle was fully open, and load was controlled by mixture enleanment (λ > 1). The reentrant piston was designed to intensify turbulence at ignition, supporting faster flame propagation and combustion stability for methane fuels, especially under lean conditions. Results showed that the custom piston consistently delivered lower COVimep, shorter combustion durations, and higher thermal efficiency compared to the factory geometry. Dethrottled operation significantly reduced specific fuel consumption at low loads and improved indicated efficiency, despite increased THC. These effects were mitigated in part by improved combustion quality from the custom piston. Overall, the combination of dethrottling and optimized piston design offers a promising approach to improving the performance of natural gas engines operating under partial-load conditions.
Silva, Cristian Douglas Rosa da, Garlet, Roberto Antonio, Dapper, Jackson Mayer, Fagundez, Jean Lucca Souza, Lanzanova, Thompson Diórdinis Metzka, Martins, Mario Eduardo Santos
Investigation of the Performance and Emissions of a Compression Ignition Mechanical Engine Operating in a Dual-Fuel Mode with Diesel and CNG2025-36-012712/18/2025
This study investigates the impact of adding compressed natural gas (CNG) to diesel on the performance of a compression ignition engine. In diesel dual-fuel systems, CNG is used to replace part of the energy originally supplied by diesel. The objective is to evaluate the performance of an Agrale BX6110 agricultural tractor engine operating in dual-fuel mode, with simple adaptations that allow it to function in its original mode as well, ensuring easy reversibility. Additionally, CNG can represent a cost-effective and environmentally advantageous alternative for farmers, significantly reducing their operational costs. Tests were conducted with four different CNG injection cases and three diesel injection cases, using an AW Dynamometer NEB 200 test bench. The maximum diesel substitution by CNG was 45.20%. In dual-fuel mode, the engine achieved maximum torque and power values of 665 N·m and 37.3 kW, respectively, representing a 20.45% loss compared to diesel-only operation. A reduction of 20.50% in carbon dioxide (CO2) emissions was observed, while unburned hydrocarbon emissions increased by approximately 4.52 times. Through economic analysis, it was concluded that, at the point of maximum torque and power operating in dual-fuel mode, a cost reduction of 14.32% per kWh produced was achieved.
Oliveira, Lucas, Alvarez, Carlos Eduardo Castilla, Cesar, Felipe
Study of the Performance, Consumption and Range of a Fuel Cell Electric Vehicle Powered by Green Hydrogen2025-36-000712/18/2025
Ethanol is a hydrogen-rich liquid and has a specific energy of 8.0 kWh/kg. In a vehicle, hydrogen storage is done in high-pressure cylinders. The same fundamental technology is used at other fuel cell systems in vehicles such as Toyota Mirai and Honda Clarity. Hydrogen is also introduced into the cell to generate electricity, which will power an electric motor that drives the vehicle. Excess electricity is stored in batteries. The main characteristic of the system described here is that hydrogen can be generated through an additional process in a reformer, installed at a fixed station. The reformer transforms the ethanol stored in the fuel station tank into hydrogen, which can then fuel a vehicle equipped with high-pressure cylinders and fed into the fuel cell. The system, however, emits water vapor, heat, and CO2. This is because carbon dioxide is a byproduct resulting from the transformation of ethanol into hydrogen. According to studies, despite this the system is carbon neutral, considering the total cycle. That is, the CO2 released into the atmosphere is retained by the plantations that are cultivated to produce ethanol. Thus, the carbon is contained in a closed cycle. In addition to ethanol, the reformer can also operate with other fuels such as natural gas, biogas, etc. In view of these facts, we have the following considerations: the use of an electric traction system with a fuel cell powered by reformed hydrogen gas from ethanol can allow greater autonomy for electric vehicles, reducing the dependence on electric charging stations; it can also make a significant contribution to reducing pollutant emissions. Looking at the world situation in the medium term, it may turn out to be an alternative system to the use of internal combustion engines and reduce dependence on fossil fuels.
Fontana, Romeu
Multi-Objective Optimization of Oxyfuel Gas Engine Using Stochastic Engine Model and Detailed Chemistry2025-01-052911/25/2025
The energy transition initiatives in Germany’s renown coal mining region Lusatia have driven research into Power-to-X-to-Power technologies, where synthetic fuel is produced from renewably sourced hydrogen and captured CO2, and converted to electricity and heat through oxyfuel combustion. This work investigates the multi-objective optimization of oxyfuel gas engine using a stochastic engine model and detailed chemistry. Exhaust gas recirculation (EGR) rate, initial cylinder temperature and pressure, spark timing, piston bowl radius and depth are selected as design parameters to minimize the exhaust temperature at exhaust valve opening and indicated specific fuel consumption (ISFC) corresponding to oxyfuel operation with different dry and wet EGR rates. The optimization problem is solved for a dry EGR and four wet EGR cases with various CO2/H2O fractions, aiming to achieve comparable performance as in conventional natural gas / air operation, and energy-efficient carbon capture. The case with the lowest humidity (T10deg) had the lowest temperature of 1537 K, while the one with the highest vapor fraction (T70deg) attained the minimum 260 g/kWh ISFC. The superiority of the T10deg case is offset by much higher cooling demand (3.06 kW) for CO2 separation than that for T70deg case (0.81 kW). The constraint for combustion efficiency (>65%) limited the solution space towards high ISFC values, while the constraint for low indicated mean effective pressure (IMEP) (>7 bar) and the constraint for high IMEP (<8 bar) limited the solution space in between the two distinct clusters of feasible designs, and towards high exhaust temperature, respectively. The optimized designs from all the cases could outperform the reference case in terms of IMEP, nevertheless they fell below 31% indicated efficiency, which is associated with stoichiometric combustion.
Asgarzade, Rufat, Franken, Tim, Mauss, Fabian
Sustainable Engines with Carbon-Neutral Fuels – Fast Adaptation for Efficient Multi-Fuel Operation by Tailored Charge Motion Design2025-01-053411/25/2025
As a fundamental element of measures to reduce the carbon footprint of commercial applications, carbon-neutral fuels are increasingly coming into focus for heavy installations. In addition to diesel substitute fuels, alternative energy carriers like NG, H2, MeOH and NH3 are gaining increasing attention. The energy conversion of these fuels is typically taking place on the principle of premixed combustion, which places different demands on fuel injection and mixture formation, as compared to optimized diesel-like combustion. Accordingly, the demand to layout multi-fuel capable engine designs centers to a high share on the above-mentioned design that can burn these different fuels with high efficiency and support a high degree of commonality with the in-series engine to carry over reliable operation and to maintain attractive cost figures. FEV has developed the Charge Motion Design (CMD) process, which can be applied to design the intake ports and combustion chambers for multi-fuel cylinder heads in the initial phase. This advanced methodology features the capabilities to predict the performance of different configurations for the various fuels based on condensed and simplified CFD simulations and dedicated post-processing routines. These correlations are tuned and calibrated to representative engine data for individual fuels to determine the characteristics. This paper highlights the detailed application of the CMD process for cylinder head and combustion chamber definition on the base of measurements on a state-of-the-art modular single-cylinder HD engine. Six configurations of the port designs and charge motion concepts were investigated. A comparison of the concepts was first performed with the CMD fuel correlations for H2. Three concepts with varying degrees of tumble were chosen for further detailing. The results of the case study are presented along with supporting engine measurements. In addition to previously tuned correlations, new measurements with NH3 were used to calibrate and synchronize the correlations of the CMD process. A dedicated variant of the DI H2 injection in addition to the ammonia port injection was investigated as well. The CMD fuel correlations were correlated to the testing data and later applied to all configurations to evaluate their performance and suitability. This technical study highlights the potential of CMD-driven design to enable flexible, efficient, and cost-effective multi-fuel combustion.
Koerfer, Thomas, Dhongde, Avnish, Boberic, Aleksandar, Zimmer, Pascal, Pischinger, Stefan
Decarbonizing Off-Highway Vehicles: Fuel Alternatives and Implementation Strategies2025-28-023011/6/2025
Off-Highway Vehicles (OHVs) — including mining trucks, construction machinery, and agricultural equipment — contribute significantly to greenhouse gas (GHG) emissions and local air pollutants due to their dependence on fossil diesel. Achieving sustainable development goals in off-highway sectors requires transitioning toward alternate fuels that can reduce CO₂, NOₓ, and particulate matter (PM) emissions while maintaining performance and reliability. This paper comprehensively evaluates alternate fuels such as biodiesel, renewable diesel, compressed and liquefied natural gas (CNG/LNG), liquefied petroleum gas (LPG), hydrogen, and alcohol-based blends. Using insights from Service Bulletins, fuel standards, and the Worldwide Fuel Charter, it discusses fuel properties, engine compatibility, operational challenges, sustainability impacts, economic feasibility, safety considerations, and regulatory aspects. Case studies of alternate fuel deployment in OHVs illustrate practical challenges and successes. Recommendations are made for fuel selection, system modifications, and future research to support sustainable operation of OHVs.
Mulla, Tosif, Thakur, Anil, Tripathi, Ashish
Development of a Combined Injection and Ignition Unit for a Gas Engine with Direct Hydrogen Injection Integrated into the Standard Spark Plug Access Hole2025-32-005911/3/2025
To achieve the desired fuel switch from natural gas to hydrogen in internal combustion engines for combined heat and power units, it is necessary to make some adjustments to the fuel supply system. External gas mixers increase the probability of backfiring when natural gas is replaced by hydrogen. In addition, the low density of hydrogen results in a loss of power. Therefore, direct gas injection is preferred when using hydrogen. A drawback of direct injection is the requirement of higher injection pressures to achieve the desired fuel mass and mixture homogeneity as well as the additional access to the combustion chamber for the direct gas injector in the cylinder head. This paper proposes an alternative approach that does not necessitate the implementation of a high-pressure direct injection system nor additional access to the combustion chamber via the cylinder head. A combined injection and ignition unit, called HydroFit, was developed which uses a sleeve inside the spark plug bore to supply hydrogen to the combustion chamber. The hydrogen is injected into the combustion chamber via capillaries integrated into the sleeve with a moderate pressure below 1.5 MPa. Hydrogen quantity is controlled by PFI solenoid valves which are protected from combustion chamber pressure by check valves. The spark plug is mounted inside the sleeve. The HydroFit prototype was tested on a naturally aspirated single cylinder gas engine at an engine speed of 1500 rpm. A parameter variation was conducted to analyse the influence of the combustion phasing as well as the start and the end of the injection on performance and NOx emissions. The results were compared to operation with port fuel injection. The results confirm that the general concept of the HydroFit unit is functional, achieving 75% of the targeted hydrogen mass flow. However, hydrogen slip caused by the low hydrogen mass flow, combined with the high volume inside the sleeve, results in decreased engine power. Compared to port fuel injection, the NOx emissions are slightly higher, presumably due to poorer mixture homogenisation.
Rischette, Nic, Holzberger, Sascha, Helms, Sven, Kettner, Maurice
Performance Analysis of a Hydrogen-blended Naturally Aspirated Gas Engine with a Dedicated Exhaust Gas Recirculation System2025-32-004611/3/2025
With the publication of the Renewable Energy Directive (RED) III in 2022, the European Union increased its renewable energy consumption target to 42.5% by 2030. Consequently, gaseous fuels derived from renewable electricity, particularly green hydrogen, are expected to play a pivotal role in the decarbonization of the energy sector. One promising application of green hydrogen is its integration into combined heat and power (CHP) plants, where it can replace natural gas to reduce CO2 emissions. Pure hydrogen as fuel or blended with natural gas has demonstrated potential for lowering both pollutant emissions and fuel consumption while maintaining or even enhancing engine performance. But it is expected, that the amount of available green hydrogen will be limited in the beginning. So new engine systems with hydrogen and natural gas for CHP plants are required, that offer more CO2-benefit and NOx reductioon than from fuel substitution only. In the LeanStoicH2 project, a novel approach was developed to optimize the operation of a four-cylinder stationary gas engine for hydrogen utilization. The project introduced a customized exhaust gas recirculation (EGR) system in which the exhaust gas from a hydrogen-fueled cylinder is fully recirculated into the intake mixture of three other cylinders operating stoichiometrically with natural gas. This configuration leverages the benefits of both lean and stoichiometric combustion strategies. After passing a lower temperature condenser, the dry recirculated exhaust gas, which is CO2- and H2O-free, dilutes the intake mixture of the three cylinders, mimicking lean operation and thus increasing engine efficiency due to the higher isentropic coefficient (κ). Simultaneously, this approach reduces combustion temperatures, thereby lowering knock tendency and engine wear. Furthermore, the stoichiometric operation of the EGR-receiving and emission relevant cylinders allows for the effective use of a three-way catalyst, significantly reducing pollutant emissions. Experimental results confirm that this innovative combustion strategy enhances indicated efficiency from 41.5% to 43.5% compared to series operation, and maintains low NOx tail pipe emissions. These findings highlight the potential of advanced hydrogen combustion strategies to improve the sustainability and performance of gas engine CHP plants, supporting the transition toward a greener energy landscape.
Salim, Naqib, Beltaifa, Youssef, Kettner, Maurice
Effects of Intake-Air Heating on a Light-Duty CNG-Diesel Reactivity-Controlled Compression Ignition Engine2025-32-000311/3/2025
Reactivity controlled compression ignition (RCCI) is a promising low-temperature combustion strategy that offers high thermal efficiency with reduced nitrogen oxides (NOx) and soot emissions. However, at low loads, RCCI operation often suffers from incomplete combustion, leading to elevated partial combustion products, such as, unburned total hydrocarbons (THC) and carbon monoxide (CO) emissions. Intake-air heating is a potential strategy to address these issues by enhancing fuel reactivity and promoting more complete combustion. In this study, the effects of intake-air heating (from ambient to ~95°C) on performance, combustion, and emissions were experimentally investigated in a light-duty diesel engine operated in compressed natural gas (CNG)-diesel RCCI mode. Experiments were conducted at low and intermediate loads at various engine speeds. A single injection strategy was employed for low-load, while a double-injection strategy was used at intermediate-load operating condition s. CO and THC emissions were significantly reduced at low loads with intake-air heating, but at intermediate-loads no significant reductions in CO and THC emissions were observed. However, NOx emissions increased and combustion stability improved with intake-air heating at all the investigated operating conditions. Furthermore, increased intake-air temperature at low-load high-speed operation with single injection strategy resulted in significant combustion oscillations due to end-gas auto-ignition. The presence of oscillations was confirmed by a fast Fourier transform (FFT) analysis of the in-cylinder pressure that revealed significant resonance in the first circumferential mode at higher intake temperatures. Furthermore, with intake-air heating, an increase in the energy substitution by CNG from 50% to 70%, and a marginal increase in EGR from 45 to 55%, improved the THC-NOx trade-off in RCCI operation.
Navaneethakrishnan, P., Sarangi, Asish K, Suman, Abhishek, Sreedhara, Seshadri, Singh, Arvind Kumar
Experimental Study of hCNG on Single Cylinder 395cc Spark Ignition Engine for Performance and Exhaust Emission2025-32-005011/3/2025
There is growing demand for energy utilization due to stricter environmental emission norms to reduce greenhouse gases and other threats posed due to the emissions are major motivation factors for researchers to adopt on strategic plans to decrease the usage of energy and reduce the carbon contents of fuels, the usage of hydrogen or blend of hydrogen with CNG as a fuel in internal combustion engines is the best option. As hydrogen has lower volumetric energy density and higher combustion temperature, pure hydrogen-fueled engines produce lower power output and much higher NOx emissions than gasoline-fueled engine at stoichiometric air-fuel ratio. Blending of hydrogen with CNG provides a blended gas termed as hydrogen-enriched natural gas (hCNG). hCNG stands for hydrogen enriched compressed natural gas and it combines the advantages of both hydrogen and methane. The addition of Hydrogen to CNG has potential to even lower the CNG emissions and is the first step towards promotion of a Hydrogen economy. hCNG allows customers early hydrogen deployment with nearly commercial technology. Spark ignition Engines can be calibrated for lower NOx and greenhouse gas emissions. Spark ignition engine is compatible to run on hCNG with minimum modifications. In the present study 395cc water cooled spark ignition engine with port fuel injection system was used to explore CNG and hCNG fuel with 18% Hydrogen in CNG for comparing engine performance and effective way to reduce emissions. A series of experiments were carried out on engine test dynamometer also on vehicle chassis dynamometer on 3-wheeler vehicles with different ignition timing, operating lambda. Hydrogen with CNG as a fuel in SI engines has shown significant positive impact on efficiency with lean lambda limits. With 18% Hydrogen in CNG make it possible to run the engine leaner, resulting in lower emission for CO2, CO, HC however with higher NOx emissions. To reduce NOx emission on engine, novel water injection technology added on engine to reduce NOx emission by 43%. Experimental study on vehicle infers emission reduction on Indian driving cycle, also reduction in CO2 emission has shown improvement in fuel consumption of vehicle on driving cycle with lean lambda, retarded ignition timing with 18% percentage of Hydrogen blended with CNG. Spark ignition engine with 18% Hydrogen in CNG fuel on three-wheel vehicle met Bharat Stage 6 emission norms. Emission result infers 41% margin in CO, 15% margin in NOx, 45% margin in HC+NOx and 9% improvement in CO2 emission which resulted in 10% improvement in fuel economy with hCNG when compare with CNG fuel. Finally, it has been said that hCNG fuels is next alternate fuel with the use of hydrogen in future vehicle fuel.
Syed, Kaleemuddin, Chaudhari, Sandip, Khairnar, Girish, Sajjan lng, Suresh
Development of Thermal Management Strategies for Refrigerant Boilers in Organic Rankine Cycle for Solar Electric Energy Conversion2025-28-041410/30/2025
Electricity is a fundamental necessity for individuals worldwide, serving as a force driving technological progress hitherto unimaginable. Electricity generation uses diverse methodologies based on available natural resources in a given geographic region. Conventional methods like thermal power from coal and natural gas, water-based hydropower, solar power from the sun, wind power, and nuclear power are used extensively, the former two being the dominant sources. The generation of nearly 70% of the world's electricity is estimated to be from thermal power plants; however, these operations lead to widespread environmental destruction, greenhouse emissions, and the occurrence of acid rain. Conventional thermal power plants run on the Rankine cycle principle of a boiler, a turbine, a condenser, and a pump. A similar method may be used in the Organic Rankine Cycle (ORC) with the use of solar energy, where heat is transferred to the working fluid in the boiler using a heat pipe, a passive heat transfer device. A closed system makes use of Liquefied Petroleum Gas (LPG) as the working fluid in the Organic Rankine Cycle, while acetone serves as the working fluid when used inside the heat pipe. The boiler is constructed to function within the pressure range of 4-7 bar, while the turbine is constructed to function at temperature levels of 150-200°C when optimized for maximum thermal efficiency. In this current research, a refrigerant boiler has been designed incorporating thermal management strategies to optimize efficiency. The rate of heat transfer from the solar collectors was analyzed under various conditions, and it was found that the evacuated tube collectors had temperature efficiencies ranging from 40-60% at various irradiation levels. Technical parameters unique to the solar collectors are an average flux of 500 W/m2 and a collector efficiency of 65% at the peak of sunlight intensity. The system can also sustain a boiler temperature of 250°C to allow for maximum system working fluid vaporization and pressure generation. The performance of the system was also subjected to different weather conditions, with particular emphasis on temperature variation and the effect on system efficiency. This research offers an insight into the development of solar-powered ORC systems with emphasis on their capability to generate clean and renewable energy. The research can also be applied to enhance the heat management of refrigerant boilers to allow for efficient temperature control and increased overall system efficiency in solar electric energy conversion.
Deepan Kumar, Sadhasivam, Kumar, V, Dhayaneethi, Sivaji, Mahendran, M, Saminathan, Sathiskumar, R, Karthick, A, Vikasraj
Effect of Flow Speed and Turbulence on Methane Combustion in a Rapid Compression Machine2025-01-039310/7/2025
Recent experimental work from the authors’ laboratory demonstrated that applying a boosted current ignition strategy under intensified flow conditions can significantly reduce combustion duration in a rapid compression machine (RCM). However, that study relied on spark anemometry, which provided only localized flow speed estimates and lacked full spatial resolution of velocity and turbulence near the spark gap. Additionally, the influence of turbulence on combustion behavior and performance across varying flow speeds and excess air ratios using a conventional transistor-controlled ignition (TCI) system was not thoroughly analyzed. In this study, non-reactive CFD simulations were used to estimate local flow and turbulent velocities near the spark gap for piston speeds ranging from 1.2 to 9.7 m/s. Simulated local velocities ranged from 0.7 to 96 m/s and were used to interpret experimentally observed combustion behavior under three excess air ratios (λ = 1.0, 1.4, and 1.6). Combustion was analyzed using pressure-based normalized cumulative heat release (NCHR) durations and high-speed shadowgraph imaging. At stoichiometric conditions (λ = 1.0), combustion duration decreased by over 70% with increasing flow speed, with optimal behavior observed between 33 and 72 m/s. At 96 m/s, durations increased again due to early spark kernel displacement and greater convective losses. For λ = 1.4, the shortest durations occurred near 23 m/s, corresponding to an 87% reduction in flame initiation time. At higher flow speeds, ignition consistency declined, with complete misfires at 72 m/s. For ultra-lean mixtures (λ = 1.6), stable combustion was only observed at low flow speeds (≤ 9 m/s); beyond this, ignition failed entirely due to heat loss and limited mixture reactivity. Shadowgraph imaging confirmed that larger, faster-growing flame kernels formed at optimal flow speeds, correlating with shorter combustion durations and higher peak pressures. At excessive flow intensities, however, early flame kernel disruption and elevated convective losses led to slower combustion or complete misfire.
Haider, Muhammad.Shaheer, Jin, Long, Yu, Xiao, Reader, Graham, Zheng, Ming
Advanced Plasma-Based Ignition Strategy for Future Spark Ignition Engines2025-24-00209/7/2025
Internal combustion engines will continue to play an important role in transportation for decades to come because of the high onboard energy density. For present passenger vehicles, efforts have been made to reduce the cold start emissions and improve engine efficiency. To reach such goals, lean and diluted mixtures are needed to reduce the chemical reactivity of the mixture, so a higher engine compression ratio can improve thermal efficiency. The decreased flame temperature of the lean/diluted mixtures is also beneficial for NOx reduction. Strong in-cylinder flow is needed to increase flame propagation speed for efficient and complete combustion process. Strong ignition sources are needed to provide robust ignition to support the combustion process. In this paper, the application of advanced plasma-based ignition strategies was reviewed, with special attention to the on-demand plasma energy profiling, which has flexible control over discharge duration and current amplitudes. The ignition performance of multi-core ignition is compared with on-demand energy profiling under cold start and engine idling conditions. For heavy-duty applications burning low and zero carbon renewable fuels with less chemical reactivity, such as ammonia and natural gas, a novel ignition source with remote chamber and detonation tube is also demonstrated for the first time. The air-fuel mixture in the remote ignition chamber can be ignited, and the flame front can propagate and accelerate along the detonation tube to detonation stage, known as the deflagration-to-detonation transition. The high-speed detonation wave has a much stronger ignition capability to improve combustion efficiency of mixture with low chemical reactivities.
Yu, Xiao, Leblanc, Simon, Reader, Graham, Zheng, Ming
Exhaust Thermal Management in a Dual-Fuel Marine Engine via Fully Variable Valve Actuation and Wastegate Lambda Control2025-24-00859/7/2025
Dual-fuel combustion is emerging as a promising solution to address the growing focus on maritime decarbonization, because it is adaptable and needs minimal system modifications. However, natural gas as an alternative fuel must deal with the issue of methane slip, because methane has greater global warming potential than CO2. Conventional aftertreatment systems may incorporate a methane oxidation catalyst to mitigate methane emissions, but effective methane oxidation requires high temperatures of approximately 400 °C. Therefore, exhaust thermal management (ETM) is crucial for maintaining high exhaust gas temperature (EGT) and ensuring conversion efficiency. This study investigates the effectiveness of fully variable valve actuation (VVA), including early exhaust valve opening (EEVO) and early intake valve closing (EIVC), along with lambda control via wastegate control. Each strategy’s effect on exhaust gas temperature is evaluated, while considering potential trade-offs with efficiency. The research uses a model-based approach, simulating a state-of-the-art, six-cylinder natural gas/diesel dual-fuel marine engine (Wärtsilä 6L20 DF), equipped with a two-stage turbocharger with wastegates. Numerical simulations are conducted using a one-dimensional (1D) engine model within GT-Suite across two different load conditions. The model is validated using baseline valve timings and a comprehensive dataset of experimental data. Results indicate that all three strategies can contribute to EGT elevation. EEVO raises EGT by 73 K, but incurs a 3.85% reduction in brake thermal efficiency (BTE). EIVC achieves a substantial EGT increase of 122.7 K at medium load, with a slight BTE improvement of 0.4%. Wastegate lambda control elevates EGT by 91.5 K at low load, exhibiting a negligible BTE impact. Thus, VVA-based ETM and lambda control enable rapid warm-up of exhaust aftertreatment systems (EATS) in large-bore engines with a minor efficiency penalty. This helps compliance with stricter emission regulations which contribute to maritime decarbonization, eventually enhancing air quality and the maritime ecosystem.
Soleimani, Amir, Kim, Jeyoung, Axelsson, Martin, Hyvonen, Jari, Mikulski, Maciej
Cylinder Balancing Algorithms: Enabling the Transition to Future Fuels in Large-Bore Spark-Ignited Engines2025-24-00179/7/2025
Large-bore spark-ignited engines equipped with individual cylinder injection systems require advanced balancing strategies to achieve optimal combustion performance and mitigate risks associated with abnormal combustion phenomena. The integration of highly reactive fuels, such as hydrogen, introduces additional challenges for high-power-density, low-speed engines. This study investigates closed-loop cylinder balancing strategies utilizing real-time cylinder pressure feedback to optimize engine operation. Key performance metrics were evaluated on a 20-cylinder medium speed stationary gas engine (8.5 MW electrical power) under eight different control strategies. The results indicate that the tested balancing methods reduce average knock intensity and variation of combustion peak pressure across all cylinders compared with original manufacturer control strategy. Furthermore, the study demonstrates that a well-balanced engine offers significant advantages, including enhanced power output, a 0.5% improvement in thermal efficiency, and a 20% reduction in NOx emissions. These findings highlight the critical role of cylinder pressure-based balancing algorithms in improving the performance, efficiency, and environmental sustainability of engines operating on natural gas and hydrogen blends. This research provides a unique experimental campaign with valuable insights into the development of next-generation combustion control systems in large-scale industrial and power generation applications.
Martelli, André, Penaranda, Alexander, Martinez, Santiago, Zabeu, Clayton, Salvador, Roberto
Toward Sustainable Heavy-Duty Transport: Evaluating Charge Dilution and Advanced Corona Ignition System Effects on SI Natural Gas Engine Efficiency and Combustion Characteristics2025-24-00249/7/2025
Reducing greenhouse gas (GHG) emissions in the transportation sector is a significant challenge. A multi-technology approach is the most practical and sustainable solution for minimizing the environmental impact of road transport. Alternative gaseous fuels derivable from bio sources have the potential to significantly cut equivalent carbon dioxide (CO2eq) emissions from a Well-to-Wheel (WtW) perspective, and the development of technologies that allow to improve the efficiency of natural gas-powered Heavy Duty (HD) Spark Ignition (SI) engines is of strategic importance. In such applications, charge dilution strategies might have the potential to increase engine efficiency at a relatively low implementation cost. Diluting the in-cylinder charge can reduce fuel consumption by decreasing wall and pumping losses, and increasing the Heat Capacity Ratio (γ). The coupling with innovative technologies aimed at enhancing ignition energy, influencing combustion development, could be a promising scientific path for achieving more significant results. This work presents an experimental study conducted on a modern natural gas HD SI Single Cylinder Engine (SCE) to analyze the efficiency and emission benefits achievable through charge dilution. Additionally, a characterization of the prototypal 2nd generation Advanced Corona Ignition System (ACIS gen2) was conducted for a preliminary assessment of its potential in gaseous fuel context, and to investigate the effects of its higher ignition energy on combustion features under both diluted and non-diluted charge conditions. The steady-state tests have been carried out across the low/medium load and speed range of the engine map, replicating the most common operating conditions for on-road use cases. The results highlight that charge dilution positively impacts the thermodynamic efficiency of gas HD SI engines within specific limits, lowering the Indicated Specific Fuel Consumption (ISFC) by up to 10%. The ACIS gen2 reduced the combustion duration, particularly impacting the early stages, producing an additional improvement in the ISFC of 1% to 2% in stoichiometric conditions; and suggested further potential that could be obtained by optimizing the entire system. Both technologies show that their use could be beneficial in hydrogen applications.
Di Domenico, Davide, Napolitano, Pierpaolo, Papi, Stefano, Ricci, Federico, Golini, Stefano, Rapetto, Nicola, Giordana, Sergio, Beatrice, Carlo
Numerical Investigation on an Injection strategy Optimization for Dual Fuel Marine Engine Fuelled by Ammonia2025-24-00139/7/2025
In the context of greenhouse gas emissions (GHG) reduction the most viable short-term solution in the maritime sector is the use of renewable carbon-free fuels. Among these, ammonia represents a possible alternative in compression ignition (CI) engines operating in dual fuel (DF) mode. Although, such fuel features low chemical reactivity, especially in lean mixtures, resulting in poor combustion efficiency, exhaust ammonia slip and low engine performance, DF combustion can be an interesting strategy to overcome such limitations. In this work a wide numerical examination of diesel injection strategies is presented, while ammonia acts as the primary fuel with energy supply around 80%. Since the original marine engine, fuelled with natural gas (NG), presents a single diesel injection, firstly, a pilot injection is added and different diesel mass shares between pilot and main are investigated, by varying the injection rate shape and the pilot start of injection (SOI). Calculations are performed with a CFD approach using ANSYS Forte® code on a closed-valve cylinder domain. The results demonstrate that with an appropriate strategy it is possible to maintain the nominal value of the indicated mean effective pressure (IMEP) with limited ammonia exhaust losses by adopting a split injection and an adequate shape of the injection profile, a parameter with a great influence on the spray evolution. Namely, a pilot SOI of 20° BTDC, with a total diesel mass of 80 mg split into two equal injections with a sine-shaped injection rate, leads to better results in terms of IMEP and ammonia emissions. Being ammonia a compound of nitrogen, particular attention is paid to NOx and N2O emissions, providing a quantification of its emission index for all simulated cases.
Cameretti, Maria Cristina, De Robbio, Roberta, Palomba, Marco
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
A Life Cycle Assessment of Potential Pathways to Increase Sustainable Aviation Fuel Yields through CO 2 Upgrading Co-located with Corn Ethanol Production13-06-03-00239/4/2025
Alcohol-to-jet (ATJ) upcycling of ethanol to sustainable aviation fuel (SAF) is an attractive emerging pathway for SAF production, especially in the US Midwest with large-scale corn ethanol production. Only 39% of the corn carbon is converted to ethanol, 20% is emitted as CO2. Capturing the CO2 to produce additional ethanol or SAF directly can increase the carbon yield. To guide technology selection, this work used life cycle assessment for several CO2-to-SAF production pathways. Additionally, improvements for corn ethanol production were explored by replacing natural gas burners with heat pumps for corn drying, which reduced the carbon intensity of corn ethanol by nearly 16%. But subsequent upgrading of the ethanol to SAF is only 4.5–20% better than conventional aviation fuel. By contrast, CO2-based alternative routes to SAF fared better, reducing carbon intensities between 83% and 90%. Gas fermentation of CO2 to ethanol with subsequent ATJ upcycling to SAF was contrasted to Fischer–Tropsch conversion of CO2 to SAF. Both streams require CO2 conversion to CO, which can be produced using reverse water–gas shift or solid oxide electrolyzer cells. The Fischer–Tropsch synthesis shows a higher reduction in carbon intensity (up to 90%) compared to ATJ (up to 84.4%). For other impact categories, such as ozone depletion, ecotoxicity, and the like, the differences are of similar magnitude. Capturing CO2 locally at the bioethanol factory and converting that CO2 to ethanol might overall be preferable with a fermentation process that is quite like bioethanol production compared to Fischer–Tropsch synthesis for which products require a new transportation infrastructure. The aviation fuel yield from ATJ can reach 90%, higher than the 50–70% yield from Fischer–Tropsch synthesis, with gasoline and diesel fuel as major by-products for which markets will shrink in the future. Overall, ATJ appears to be the best choice for CO2-to-SAF using the synergy with corn ethanol factories for quick launch.
McCord, Stephen, Talsma, Sam, Bouchard, Jessey, Zavaleta, Victor Gordillo, He, Xin, Sick, Volker
Alternative Fuels and Hybridization as Cost-Effective Pathways to Medium-Duty Greenhouse Gas Phase 3 Compliance02-18-03-00197/23/2025
The United States Environmental Protection Agency (US EPA) Greenhouse Gas (GHG) Phase 3 regulation targets a substantial reduction in GHG emissions across model year (MY) 2027–2032 class 2b-8 vehicles. This article explores the implementation of alternative fuels, such as compressed natural gas (CNG) and liquefied petroleum gas (LPG), along with powertrain hybridization as viable pathways for achieving these stringent standards in a cost-effective manner. A detailed analysis is performed on a Class-7 medium–heavy-duty (MHD) truck configuration, featuring an inline 4-cylinder 5.2-L spark-ignited (SI) engine, modeled with both CNG and LPG fuels. The vehicle’s powertrain is simulated to evaluate GHG emissions and fuel efficiency. The study further examines the impact of low rolling resistance (LRR) tires and varying tire rolling resistance coefficients (Crr) on vehicle performance. For further lowering the GHG emissions, a hybrid powertrain sizing study was performed. The simulation results indicate that hybrid powertrain configurations, when combined with LRR tires, can achieve significant CO2 emission reductions, meeting and exceeding the US EPA Phase 3 GHG targets. The powertrain with the CNG engine equipped with fuel-saving technologies such as neutral-idle, engine start–stop, and automatic engine shutdown can comply with MY 2032 standards while running 7.7 N/kN Crr tires. The hybrid powertrain with the LPG engine and 5.6 N/kN Crr tires reaches compliance with MY 2032 fleet average standards while maintaining minimal payload penalties. This research provides critical insights into the feasibility of leveraging alternative fuels and hybrid technologies to meet upcoming GHG regulations, presenting a viable pathway for manufacturers to reduce operational costs while achieving environmental compliance.
Patil, Shubham V., Smith, Edward M., Bachu, Pruthvi R., Ross, Michael G.
Experimental Evaluation of Direct and Port Fuel Injection Strategies on a Heavy-Duty Liquefied Petroleum Gas Engine03-18-03-00225/9/2025
Liquefied petroleum gas (LPG) is a popular alternative fuel in the transportation sector as a result of its favorable physical and chemical properties, availability, and relatively lower emissions compared to conventional fuels. However, much of its use is currently in light-duty applications, usually in manifold or port-injected configurations primarily due to their simplicity and ease of conversion. However, there are shortfalls in heavy-duty applications where decarbonization efforts are direly needed. The key reasons for this shortfall in alternative fuel adoption in the heavy-duty sector are the deficit in engine performance when compared to conventional heavy-duty diesel engines and the lack of specialized hardware to bridge this performance gap, for example, direct injectors optimized for LPG fuel operation on large-bore engines. To address this, this study evaluated the performance, emissions, and combustion characteristics of a heavy-duty single-cylinder research engine, the Cummins ISX15L, in direct injection (DI) mode with an injector designed for liquid LPG and in a baseline port fuel injection (PFI) mode using an off-the-shelf injector currently in use on commercially available LPG engines. The engine had a compression ratio of 9.3 and a fuel delivery system designed to supply LPG at 1.6 MPa and 17.2 MPa in PFI and DI modes, respectively. The influence of both injection strategies at different start of injection (SOI) timings, equivalence ratios, combustion phasings, and engine load conditions were then investigated. The DI strategy was responsible for the highest brake thermal efficiency (BTE) recorded on the engine, 36.9%, 7% higher than the BTE in PFI mode at the same lean engine condition. The DI configuration achieved a 39% reduction in bsNOx but increased bsCO emissions by 22% compared to PFI at stoichiometric conditions. The PFI strategy demonstrated an insensitivity to the SOI timing unlike the DI strategy, which was highly unstable at retarded SOI timings.
Fosudo, Toluwalase, Windom, Bret, Olsen, Daniel
Experimental Analysis of Pressure Pulsation Noise Phenomenon in a CNG-Powered Passenger Vehicle2025-01-01125/5/2025
Compressed Natural Gas (CNG) engines are emerging as a viable alternative to gasoline and diesel in heavy commercial and passenger transport worldwide. They offer reduced CO₂ emissions and support energy independence in regions rich in natural gas. In India, enhanced CNG infrastructure and strict emission regulations have driven OEMs to develop CNG vehicles across all segments. Moreover, from a noise and vibration standpoint, CNG vehicles are expected to deliver cabin refinement comparable to that of their fossil fuel counterparts. However, one of the major challenges associated with CNG vehicles is the excitation due to additional components like CNG Pressure Regulator, Injector et al. The operational metallic/pulsation noises are generally higher as compared to liquid fuels like gasoline due to dry nature of the CNG fuel. This paper describes in detail the pulsation noise phenomena encountered during one of the late-stage vehicle development projects. An experimental root cause analysis methodology was established to identify the structural & cavity resonances phenomena of the CNG Regulator & Low-Pressure gas column along with identification of frequencies of various CNG sub-systems. Studies were carried out to de-couple resonance behavior of the system and improve attachment point stiffness as potential improvement solutions to mitigate this noise. The study also helped to define design guidelines to avoid such issues in future similar development models.
Chatterjee, Joydeep, Ravindran, Mugundaram
Improvement of Lean Burn Characteristics with Ozone Addition in a Diesel Micro-pilot Natural Gas Engine2024-32-01044/18/2025
Ozone (O3) was introduced into the intake air in a natural gas fueled engine ignited by micro-pilot of diesel fuel, to utilize the reactive O-radicals decomposed from the O3 for the promotion of the combustion and for improvements in the thermal efficiency and exhaust emissions. Experiments were carried out in a single cylinder engine to elucidate the effects of the ozone addition under the lean burn conditions. A supercharger was employed to increase the intake air amount and vary the equivalence ratio of natural gas. The experimental results showed that the O3 addition has a limited effect on the ignition of the diesel fuel injected near top dead center, while the heat release during the flame propagation in the natural gas/air mixture was increased at the lower equivalence ratio of natural gas. Further the ignition of natural gas was promoted, resulting in the increase of the combustion efficiency and the degree of constant volume heat release. The cooling loss and the NOx emissions decreased due to the leaner burn achieved by the supercharging. Overall, the indicated thermal efficiency and the exhaust emissions can be improved by the supercharging combined with the O3 addition.
Kobashi, Yoshimitsu, Miyata, Shoki, Kawahara, Nobuyuki, Inagaki, Ryuya
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