Browse Topic: Hydrogen engines

Items (285)

3D Computational Fluid Dynamics Analysis of the Performance and Emissions of an Off-Highway Port Fuel Injection Hydrogen Engine

03-19-04-0018

7/27/2026

To fulfil the global aspiration of achieving net-zero emissions, hydrogen as a fuel seems to be one of the promising candidates. High energy density per unit mass and zero carbonaceous emissions are the two salient advantages that hydrogen offers. In the present study, a set of detailed chemistry-based 3D CFD combustion simulation has been carried on a 3-cylinder turbocharged, water-cooled port fuel injection SI Hydrogen engine to understand its optimum air–fuel ratio, compression ratio, spark timing and combustion chamber geometry. The simulations have been conducted at the full load of the rated power and maximum torque engine rpms. During simulation, the λ zone for study is restricted between 2.1 and 2.7. Two different bowl geometries (spherical and cylindrical), with two compression ratio options (12 and 14) are explored in the simulations. While the spherical bowl seems to accommodate flame front better than the cylindrical bowl, the compression ratio of 12 is a safer choice to control the maximum rate of pressure rise (dp/dθ). At full load and rated speed, the indicated thermal efficiency drops by 7.7% as the λ swings from 2.1 to 2.7, whereas the indicated specific NOx and dp/dθ drop by 99% and 81%, respectively. Similarly, at full load and maximum torque RPM, the indicated thermal efficiency drops by 6.4% with λ swing from 2.1 to 2.7, whereas the indicated specific NOx and dp/dθ drop by 99% and 91%, respectively. Beyond λ = 2.4 NOx reaches almost to zero, however, at a compromise of the thermal efficiency. The dp/dθ remains well within the acceptable limit under this scenario. To account this trade-off between the performance and emission parameters, optimum λ zone has been found out to be between 2.3 and 2.5.

Satre, Santosh Dadasaheb, Mukherjee, Nalini Kanta, Kumar, Sanjeev, Nene, Devendra

Numerical Analysis of Pre-Ignition Factors in Hydrogen Engines

2026-01-0740

7/1/2026

Numerical analysis was conducted to investigate abnormal combustion, a major challenge in efforts to improve hydrogen engine efficiency. Focusing on two factors that induce abnormal combustion—surface reactions and lubricating oil—numerical analysis examined the potential for each to trigger abnormal combustion. Furthermore, since it was confirmed that the autoignition prediction using a detailed chemical reaction mechanism deviates from experiments at temperatures around 800K, attempts were made to improve this issue. As a result, it was confirmed that surface reactions affect the chemical species ratio near the wall surface but have little effect on flame propagation. Regarding lubricating oil, two possibilities were investigated: the lubricating oil itself self-igniting and becoming an ignition source for the hydrogen mixture, and deposits generated from the lubricating oil generating heat and becoming an ignition source. The results of these investigations showed that autoignition occurs before top dead center in both cases: when lubricating oil is present in the mixture during the compression stroke and when deposits heated to high temperatures are present. This indicates that engine oil can induce pre-ignition. Furthermore, the effect of water vapor on ignition delay was investigated. Finally, it was confirmed that incorporating corrections for molecules possessing kinetic energy deviating from the Maxwell distribution under low-temperature, high-pressure conditions into the reaction rate calculation improves the prediction accuracy of autoignition around 800 K.

Moriyoshi, Yasuo, Yamane, Taichi, Wang, Zhiyuan, Kuboyama, Tatsuya

Experimental Investigation into Port Water Injection on the Transient Behavior of a Heavy-Duty Hydrogen Engine

2026-01-0743

7/1/2026

Hydrogen-fuelled internal combustion engines are a potential carbon-free propulsion solution for high-power applications such as construction machinery and heavy-duty commercial vehicles. However, compared to conventional diesel engines, hydrogen engines exhibit limitations in transient operation and at full load, primarily due to the high reactivity of hydrogen. In spark-ignited hydrogen engines, combustion anomalies represent the main constraint during performance-oriented operation, particularly during transient phases that require mixture enrichment to meet dynamic torque demands. Water injection is investigated in this study as a means to mitigate these limitations. The paper describes the implementation of a port water injection system on a heavy-duty commercial hydrogen engine and evaluates its influence on engine performance with a focus on transient operating conditions. A combustion anomaly evaluation method developed in-house is applied to quantify the effect of water injection on abnormal combustion behavior. The results show that water injection shifts the combustion anomaly limit toward richer air–fuel ratios, thereby enabling mixture enrichment up to stoichiometric conditions or under during transient load changes. Water is injected cyclically into each intake port to achieve a defined water-to-hydrogen ratio during load steps. Even at low water injection rates, a significant reduction in engine response time is observed, leading to transient torque response comparable to that of a diesel reference engine. Improved torque demand tracking is demonstrated in dynamic test cycles. In steady-state operation, the application of water injection also extends the achievable full-load operating range. Overall, the results indicate that port water injection is an effective measure for suppressing abnormal combustion in heavy-duty hydrogen engines and enables more aggressive yet stable engine calibration with minimal water consumption, contributing to diesel-like performance characteristics.

Schneider, David, Christoforetti, Paul, Kappacher, Peter, Kapeller, David, Schutting, Eberhard, Eichlseder, Helmut, Trapp, Christian

Numerical Analysis of Directly Injected Hydrogen into a High-Pressure Chamber

2026-01-0745

7/1/2026

Hydrogen Internal Combustion Engines have emerged as an option for decarbonizing heavy-duty transportation. However, injecting high-pressure hydrogen gas into pressurized combustion chambers induces complex compressible flow phenomena, including choked flow and under-expanded supersonic jet structures, which challenge conventional modeling approaches for optimizing engine performance and emissions. This study conducts a numerical investigation of transient hydrogen injection into a high-pressure argon environment, benchmarking a 2D axisymmetric Computational Fluid Dynamics (CFD) model against high-fidelity experimental optical measurements. Utilizing Ansys Fluent with a density-based solver, coupled with the k-ω SST turbulence model and species transport equations, simulations were performed at injection pressures of 6 MPa and 10 MPa into a 1 MPa ambient chamber. The simulation successfully captured fundamental compressible physics, including Mach disk formation and significant expansion cooling near the nozzle exit. Validation results revealed a strong dependency on the nozzle pressure ratio (nPR). At 6 MPa (nPR=6), the model achieved good agreement with experimental data, predicting tip penetration depth within 10% . However, at 10 MPa (nPR=10), while axial penetration depth predictions remained within the 10% error margin, they were consistently underestimated, and radial dispersion was significantly under-predicted. These discrepancies at high energy levels highlight the challenges of predicting turbulent entrainment within the current modeling framework. The results suggests that the observed deviations are likely to be caused by combined limitations related to the RANS turbulence model, the potential shortcomings of the 2D axisymmetric assumption in resolving highly transient mixing phenomena, the meshing strategy used, the constant assumption made about the coefficient of discharge, and the crucial role of the Turbulent Schmidt number (SCt).

Castilla Batun, Uriel Isaac, Alzahrani, Fahad

Investigation of Influential Parameters on the Integrated Hydrogen Argon Power Cycle

2026-37-0012

6/9/2026

This study investigates hydrogen combustion in an argon–oxygen environment for argon power cycle application using computational fluid dynamics. The numerical framework, developed based on previously validated model, is applied to examine the influence of key operating parameters on combustion efficiency and indicated efficiency under constant cycle pressure conditions. A parametric analysis is conducted to evaluate the effects of excess oxygen ratio, argon rate, start of injection, and injector discharge coefficient on ignition characteristics, combustion efficiency, and engine performance. The results indicate that less fuel injection improves combustion efficiency but leads to a significant reduction in engine load. Increasing the argon rate enhances engine thermal efficiency, primarily due to the higher specific heat ratio of argon, which improves the thermodynamic efficiency of the cycle. However, elevated argon concentrations significantly reduce combustion efficiency because of limited oxygen availability, resulting in increased levels of unburned hydrogen. The analysis further demonstrates that higher injector flow rates improve both combustion and engine efficiency. Overall, unburned hydrogen is identified as a critical limitation for the practical implementation of compression ignition hydrogen engines operating in Ar–O₂ mixtures; however, unburned hydrogen levels up to approximately 8% can be tolerated without significant deterioration in combustion efficiency in next engine cycle. The results revealed that the combustion inefficiency arises due to tale combustion phase and is attributed to inappropriate mixing of fuel and oxidizer.

Chitsaz, Iman, Ahammed, Sajid, Kakoee PhD, Alireza, Salahi, Mohammad Mahdi, Andwari, Amin, Ahmad, Zeeshan, Hyvonen, Jari, Mikulski, Maciej

Combined EGR-Air Dilution Effects on Performance, Combustion and Emissions of a Single-Cylinder Spark-Ignition Direct-Injection Hydrogen Engine

2026-37-0009

6/9/2026

Hydrogen internal combustion engines (H2ICE) have emerged as a promising solution for decarbonisation of the transport sector, due to low cost and potential for rapid deployment. However, abnormal combustion and high nitrogen oxide (NOx) emissions limit stoichiometric operation, making dilution strategies essential. While lean combustion has been widely studied, combined dilution strategies of air and exhaust gas recirculation (EGR) require further investigation. This work presents experimental results from a boosted 0.5-litre spark-ignition direct-injection single-cylinder research engine equipped with high-tumble ports and cooled high-pressure EGR. Relative air–fuel ratios (lambda) of 1 to 3 and EGR rates of 0 to 40% are evaluated at 5, 10, and 15 bar of indicated mean effective pressure (IMEP) at 2000 rpm to assess effects on net indicated thermal efficiency (nITE), combustion, and emissions. A peak nITE of 43.5% is achieved at 10 bar IMEP, λ = 2.5, and 30% EGR, which can be primarily attributed to low heat losses while maintaining lower combustion losses than at higher dilution levels. NOx emissions are effectively mitigated with increasing EGR and are largely independent of lambda at 5 bar IMEP under EGR dilution. At high load, EGR is shown to be beneficial to achieve high efficiency and lower NOx at lower dilution rates, thereby reducing boosting requirements. Equivalent dilution parameters are used to investigate combined effects of EGR and air dilution, from a mass dilution perspective with the mass dilution rate (MDR) and equivalent thermal reduction with the thermal dilution parameter (TDP). Indicated efficiency and unburned hydrogen emissions correlated strongly with MDR, while temperature-dependent parameters showed a high correlation with TDP. At constant engine speed, burn durations are shown to depend mainly on degree of thermal dilution, with no effect of load observed. At high dilution rates, combustion became increasingly insensitive to further dilution, indicating the presence of thermodiffusive instabilities under high levels of both EGR and air dilution.

King, Aidan, Islam, Reza, Pickering, Simon, Yuan, Hao, Mudge, Henry, Giles, Karl, Goyal, Harsh, Jones, Peter, Akehurst, Sam, Esposito, Stefania

Impact of Compression Ratio and Stroke on Hydrogen Requirement for Emission-Optimized Operation of an Ammonia-Fuelled Spark-Ignition Engine

2026-37-0030

6/9/2026

Ammonia (NH3) fuelled engines have emerged as a promising route toward net-zero emission targets due to NH3’s carbon-free nature, ease of storage, and established handling infrastructure. However, the low laminar burning speed and narrow flammability limits of NH3 pose a significant combustion challenge, which can be addressed through hydrogen (H2) co-fuelling. For practical implementation, on-board H2 production via thermal catalytic cracking of NH3 is an attractive solution, as it eliminates the need for external H2 storage and associated handling and capital costs. Previous studies by the present authors identified a lean operating strategy that achieves an equimolar ratio of NOx and unburned NH3 (α NH3NOx ≈ 1), enabling complete conversion to nitrogen and water vapour when coupled with a Selective Catalytic Reduction (SCR) system. This strategy was further validated using cracked NH3 derived H2 in place of bottled H2 through an on-board cracker, thereby representing a practical system configuration. However, the required H2 fraction, and consequently the size and power demand of the onboard cracking system, is strongly influenced by engine architecture and operating conditions. The present study investigates the effect of compression ratio (CR) and stroke length, on H2 fraction requirements to achieve an optimum α of unity in an externally boosted SI engine. Results demonstrate that the high CR = 17.5, long stroke configuration reduces H2 enrichment by 50–60% compared to a low CR = 12.5, short-stroke engine architecture, allowing smaller onboard H2 generation systems. At high-speed, high-load conditions, it achieves over 45% thermal efficiency with stable NH3 combustion and no H2 supplementation, maintaining an α ≈ 1. Across the full operating map, NOx emissions comply with IMO Tier III and EPA Tier 4 norms, demonstrating near-zero-emission operation.

Yadav, Neeraj Kumar, Ambalakatte, Ajith, Geng, Sikai, Gopakumar Suja, Gagan, Birch, Alexander, Cairns, Alasdair, Harrington, Anthony, Hall, Jonathan

Predictive Modelling of NO _x and Unburned Hydrogen Emissions in a Direct-Injection Hydrogen Spark-Ignition Engine

2026-37-0007

6/9/2026

Hydrogen is emerging as a compelling energy carrier for future transportation due to its potential to enable fully decarbonised operation and near-zero tailpipe pollutant emissions. Realising this potential in reciprocating internal combustion engines requires a detailed understanding of the complex interactions governing hydrogen combustion and emissions formation. In this context, physics-based reduced-order emission predictive modelling offers a powerful means to accelerate the development and optimisation of hydrogen-fuelled engines by enabling rapid evaluation of operating strategies without the need for extensive experimental campaigns. This study investigates the simulation of nitrogen oxides (NOx) and unburned hydrogen (uH2) emissions from a 0.5L spark-ignition direct injection single-cylinder research engine within a 1D-0D simulation approach. For NOx prediction, a simplified kinetic mechanism is coupled with both a 0D two-zone combustion model and a thermal multi-zone in-cylinder representation, enabling assessment of the need to account for temperature stratification for accurate prediction. For uH₂ emissions, phenomenological sub-models describing flame wall quenching and top-land crevice mechanisms are implemented and calibrated to capture the dominant sources of hydrogen escape during combustion. The models are validated against an experimental dataset spanning a wide range of engine conditions, including variations in engine load, relative air–fuel ratio from stoichiometric to ultra-lean combustion, dilution via exhaust gas recirculation, and spark timing. The comparison highlights the models' ability to reproduce observed physical trends across different engine operating conditions for both NOx and uH2. Regarding NOx emissions, the accounting of temperature stratification with the multi-zone model enables more accurate predictions of trends and absolute values. The uH2 model provides fundamental insights into hydrogen engine flame propagation by highlighting the need for flame propagation in the top-land crevice at richer λ to reproduce observed trends. Overall, the study provides insights into both hydrogen-specific emission mechanisms and key modelling requirements for accurate pollutant simulation in hydrogen engines.

Malfi, Enrica, De Felice, Massimiliano, Esposito, Stefania, Ribnishki, Aleksandar, King, Aidan, Akehurst, Sam, Jones, Peter, Goyal, Harsh

TOC

99-08-02-0TOC

4/13/2026

TOC

Tobolski, Sue

CuSCR Catalysts Under H ₂ -ICE Exhaust Gas Conditions

2026-01-0361

4/7/2026

In the near to mid-term, hydrogen internal combustion engines (H2-ICE) can be a bridge technology for reducing carbon emissions. A few challenges anticipated under lean-burn H2-ICE operation are the significant drop in turbo-out temperatures, combined with higher water content, and the possible presence of unburned hydrogen in the exhaust, which could have a potential impact on performance and durability of the downstream exhaust aftertreatment system, particularly oxidation and SCR catalysts, as these conditions can suppress low-temperature oxidation activity, perturb Cu-site speciation and redox cycling in SCR catalysts, and exacerbate hydrothermal aging under sustained wet operation. This study examines the impact of excess water and residual hydrogen on Cu-SCR durability, active site chemistry, and stability for the case with and without an upstream oxidation catalyst, through aging tests at 450 °C and 550 °C. Changes in Cu redox cycles were assessed through site quantification using multiple titration techniques to determine the influence of excess H2O and H2 on catalyst performance and aging.

Kim, Mi-Young, Daya, Rohil, Kamasamudram, Krishna

Model-Based Development of a Heavy-Duty H ₂ -ICE and Integrated, Turbogeneration, Electrification, and Supercharging (ITES) System

2026-01-0426

4/7/2026

Changing global economic conditions and efforts to reduce greenhouse gas emissions are driving the need to develop efficient, near-term, alternative propulsion system technologies for heavy-duty vehicles. This study combines a hydrogen internal combustion engine (H2-ICE) with electrically assisted turbocharging, exhaust energy recovery, and mild hybridization to maximize propulsion system efficiency and reduce NOx emissions. To reduce cost and packaging impact of integration of these technologies on an engine, the study presents a model-based development and optimization of an Integrated Turbogeneration, Electrification, and Supercharging (ITES) system that combines the enabling components into a single compact unit. In the first phase of this study, a H2-ICE and aftertreatment concept for a MY2027 7.7L medium heavy-duty on-road engine was developed and evaluated through 1D simulation. The concept was to convert a diesel engine by changing the cylinder head to implement a port fuel injection (PFI) lean H2 SI combustion system with two-stage turbocharging and no external EGR. The concept was optimized for compression ratio, valve lift profiles, turbocharging, aftertreatment size/specification, and calibration using 1D system simulation in GT-SUITE. In the second phase of this study, the H2-ICE concept performance was further improved by integrating the ITES system and evaluated through 1D simulation. The ITES system replaces the conventional low-pressure stage of the boosting system and adds the capability of electrically assisted turbocharging, turbogeneration from exhaust energy, and P1 mild-hybridization. Applying a model-based approach, the H2-ICE & ITES component sizes were optimized for the best performance and emissions benefit. Using 1D simulation of validated models, the efficiency benefit of the ITES system on engine and vehicle level system was predicted. Finally, a vehicle level simulation was conducted comparing the fuel consumption between a conventional advanced boosting system H2-ICE concept and H2-ICE+ITES concept for Class 6-7 medium heavy duty truck application.

Bustamante, Oscar, Correia Garcia, Bruno, Joshi, Satyum, Franke, Michael

Effects of the Spark Location and Timing in a Heavy-Duty Hydrogen-Fueled Engine

2026-01-0331

4/7/2026

The use of hydrogen in internal combustion engines offers a promising route to lower-carbon propulsion in heavy-duty transportation. However, its distinct combustion characteristics as high flame speed, wide flammability limits, and susceptibility to abnormal combustion, necessitate careful engine and ignition system design. This study numerically investigates the combined effects of spark plug (SP) location and ignition timing on the performance of a heavy-duty diesel engine converted to spark-ignition and operated with hydrogen as fuel at reduced compression ratio. The numerical study aims to guide engine design. Three-dimensional computational fluid dynamics simulations with detailed hydrogen chemistry were conducted to evaluate flame development, and relevant combustion metrics under different loads. Model validation against engine combustion data and hydrogen injection from a low-pressure, high-mass-flow direct injector are also presented. The results demonstrate that SP placement is pivotal to control for combustion stability and efficiency due to the complex in-cylinder mixing and stratification associated with direct hydrogen injection. For each load, optimal ignition timings were identified. Highlights demonstrate the feasibility of installing the SP close to the jet-forming cap (injector tip) to exploit local enrichment and enhance flame propagation.

Menaca, Rafael, Shakeel, Mohammad Raghib, Panithasan, Mebin, Liu, Xinlei, Qahtani, Yasser, AlRamadan, Abdullah, Cenker, Emre, Silva, Mickael, Pei, Yuanjiang, Turner, James, Im, Hong

Physics-Based Simulation for Sustainable Fuels Part 1: Simulation-Driven Hydrogen Engine Power Cylinder Unit Optimization and Experimental Confirmation

2026-01-0278

4/7/2026

The demand for sustainable mobility and transportation is accelerating the adoption of alternative fuels, particularly hydrogen, in internal combustion engines. However, these engines present specific risks, such as flammable crankcase gas accumulation from blow-by and irregular combustion resulting from oil transport into the combustion chamber. Addressing these challenges requires advanced simulation tools to optimize power-cylinder-unit performance, specifically piston ring and gas dynamics. This study demonstrates the success of physics-based 2D simulation for hydrogen PCU design optimization, focusing on blow-by reduction and control of gas-flow-driven oil transport. Unlike commercial codes with adjustment and fitting parameters, the 2D simulation code – developed by Massachusetts Institute of Technology and successfully applied by MAHLE over decades – is fundamentally physics-based, enabling direct predictive capability without empirical calibration. Leveraging the validated “Healthy PCU System” design methodology 2D ring and gas dynamics models guided component optimization across the entire operating map. Comprehensive engine testing on a hydrogen-fueled platform confirmed simulation predictions, achieving a 28% reduction in blow-by and elimination of reverse-flow-driven oil transport. The optimized PCU design demonstrated significant improvements in lube oil consumption, with reductions of 5 g/h during high-load operations directly addressing hydrogen engine safety and performance requirements. While 2D simulation delivers excellent trend accuracy and captures average system behavior, it cannot resolve three-dimensional effects - such as ring and bore distortion conformability or ring gap positioning and ring rotation phenomena – which are responsible for local oil emissions or irregular combustion. Complementary 3D simulation analysis, combined with detailed inter-ring pressure measurements, provides essential insights into these localized phenomena and real engine behavior, as demonstrated in Part 2 of this publication series. As a further step, 3D oil transport simulation and lube oil consumption range prediction will be conducted as Part 3 of this publication series. This publication series establishes 2D simulation as the essential, computationally efficient tool for precise and efficient PCU development, while confirming that 3D analysis and experimental inter-ring pressure measurements are necessary to fully understand complex ring-liner interactions across multiple engine platforms.

Köser, Philipp, Moreira, Rui, Deuß, Thomas, Morgado, Leonardo

CFD-Guided DoE-ML Optimization Methods in a Heavy-Duty Hydrogen Engine

2026-01-0326

4/7/2026

This study introduces a CFD-guided design of experiments (DoE) and machine learning (ML) framework for the co-optimization of piston and pre-chamber geometries in a passive pre-chamber heavy-duty hydrogen engine operating at medium and low loads. Starting from a reference configuration, an omega-type piston and a methane-optimized pre-chamber, the design space was parameterized using seven geometric variables. A Sobol sequence was employed to generate 96 randomized design variants in the DoE, each evaluated through high-fidelity 3D-CFD simulations to capture key combustion and performance metrics. The resulting dataset served as the foundation for developing and evaluating several ML regression models. A rigorous ML workflow was adopted, featuring 5-fold cross-validation and hyperparameter tuning via Bayesian optimization to ensure generalization and robustness. Model selection was based on multi-metric performance criteria including prediction accuracy, error stability, and sensitivity to design changes. The selected model demonstrated strong predictive capabilities across the design space and was integrated into an iterative optimization loop that continuously refined geometry predictions by incorporating additional CFD runs. This adaptive simulation-learning framework led to improved model accuracy and enabled rapid exploration of high-potential design regions. Beyond reducing time for technology deployment relative to expert-guided design strategies, the ML models offered interpretability by exposing key geometric sensitivities and highlighting high-impact design directions for enhanced hydrogen combustion.

Menaca, Rafael, Shakeel, Mohammad Raghib, Liu, Xinlei, Mohan, Balaji, AlRamadan, Abdullah, Cenker, Emre, Silva, Mickael, Zhang, Anqi, Pei, Yuanjiang, Im, Hong

Physics-Based Simulation for Sustainable Fuels Part 2.2: Inter-Ring Pressure Measurements and 2D/3D Ring Dynamics Analysis across Multiple Engine Platforms – Heavy Duty and Large Bore

2026-01-0280

4/7/2026

The growing demand for sustainable mobility and transportation is accelerating the adoption of alternative fuels, particularly hydrogen, in internal combustion engines. The first part of this publication series highlights the significance of 2D simulation as a crucial and computationally efficient tool for the precise development of hydrogen Power Cylinder Units. This approach demonstrates predictive capability proofed through engine tests, achieving a reduction in lube oil consumption by 5 g/h during high-load operations, alongside a 28% decrease in blow-by and an 11% reduction in hydrogen flow to the crankcase. To provide deeper insights into the complexities identified in Part 1, this study employs inter-ring pressure measurements across various engine types and configurations, including light vehicles, heavy-duty trucks, and large-bore applications, covering a broad range of engine displacements from 2 to almost 100 liters. Part 2.1 focuses on understanding the cyclic variations and mechanisms that lead to oil emissions during low-load operations at a light vehicle, while this investigation in Part 2.2 focuses on upper compression ring instabilities, cyclic variation in a heavy-duty engine and as well as the factors contributing to irregular combustion phenomena at a large bore engine. Complementing predictive 2D simulations and inter-ring pressure measurements, targeted 3D analyses are performed for capturing three-dimensional effects such as bore distortion and ring conformability. These analyses yield valuable insights into oil transport mechanisms that can contribute to irregular combustion. Part 3 of this publication series will concentrate on 3D oil transport simulations and optimization, including predictions of absolute lube oil consumption ranges of the hydrogen engine discussed in Part 1, while building on the valuable insights gained from the in-depth investigation of Part 2.

Köser, Philipp, Moreira, Rui

Heavy Duty Hydrogen Internal Combustion Engine Emissions Development to Achieve Ultra-low NOx

2026-01-0356

4/7/2026

This paper presents the emissions development of a heavy-duty hydrogen internal-combustion engine (H₂ICE) targeting ultra-low NOx with a design goal of 20 mg/hp-hr. The approach integrates advanced thermal management of the engine and aftertreatment, including engine out NOx management through air-fuel ratio controls and an electric heater to accelerate catalyst light-off and sustain activity at low-load/idle conditions. A diesel-derived aftertreatment system (ATS) is selected to maximize practicality and component commonality, and an integrated controls strategy spanning the engine and ATS is implemented to demonstrate ultra-low NOx capability over EPA certification cycles. The paper concludes with considerations for periodic SCR regeneration to ensure emission compliance.

Shakya, Bijesh, Xu, Hui, Yang, Zhao, Stetter, John

Advanced Multifunctional Catalysts for Emission Control in Hydrogen and Diesel Engines

2026-01-0367

4/7/2026

As hydrogen internal combustion engines (H2-ICE) gain traction, optimizing exhaust aftertreatment technologies for nitrogen oxide (NOx) control has become increasingly critical. While selective catalytic reduction (SCR) systems remain the primary approach for NOx mitigation, oxidation catalysts are also being explored to facilitate hydrogen oxidation and improve overall exhaust treatment efficiency. This work presents a multifunctional catalyst (MFC) concept that combines supported Pd and Cu-zeolite to enable simultaneous NOx reduction and hydrogen oxidation within a single catalytic unit. Preliminary results show that hydrogen oxidation on supported Pd occurs above 300 °C, while Cu-zeolite achieves nearly complete NOx conversion. Experiments on individual components indicate that supported Pd initiates ammonia oxidation only after hydrogen is depleted. In the presence of hydrogen, ammonia conversion remains below 20%, indicating that hydrogen availability suppresses ammonia oxidation, which is favorable for SCR operation. The MFC can be configured either on a substrate or as an on-filter catalyst (MFCoF), providing simultaneous chemical conversion and urea-derived particulate filtration. In addition to hydrogen engines, the MFCoF concept can be applied to diesel and biodiesel engines, enabling effective filtration of soot particles while maintaining NOx reduction performance along with hydrocarbon oxidation capability. By combining NOx reduction, hydrogen/hydrocarbon oxidation, and particulate filtration in one unit, the MFCoF approach provides a promising pathway for next-generation exhaust systems across diverse engine platforms.

Danghyan, Vardan, Becker, Jan Martin, Hünnekes, Edgar, Patchett, Joseph

Experimental Study on the Effect of Ignition Strategy on Combustion and Emissions in a Direct Injection Hydrogen Engine

2026-01-0330

4/7/2026

Hydrogen-fueled internal combustion engines (H₂ICEs) are a promising pathway toward carbon-neutral transportation, but their efficiency and emissions performance are highly sensitive to ignition control strategies. This study systematically investigates the combined effects of spark timing (−10 to −26 °CA BTDC) and spark energy (25–40 mJ) on combustion characteristics in a direct injection H₂ICE operating at a constant speed of 1400 r/min under low, medium, and high load conditions. Results show that spark timing advance produces load-dependent effects: at low load, it increases the peak heat release rate while delaying peak pressure and shortening combustion duration; at medium and high loads, it advances both peaks toward TDC with an optimal spark timing shifting closer to −14 °CA. Ignition delay was only slightly reduced at low load but significantly shortened by about 3 °CA at high load. NOx emissions increased nearly linearly with spark advance, while slight retardation effectively halved NOx at low load without compromising torque. Increasing spark energy reduced ignition delay by up to 23% and shortened combustion duration by 2–4 °CA at low load, resulting in a torque increase from 48 to 60 N·m; however, the benefits diminished with increasing load. Additionally, higher spark energy led to a moderate NOₓ rise, particularly under medium load. These findings offer valuable insights into the optimization of ignition strategies for H₂ICEs, providing a foundation for improving combustion efficiency while minimizing emissions in zero-carbon hydrogen-powered engine systems.

Zhao, Keqin, Lou, Diming, Zhang, Yunhua, Fang, Liang, Tan, Piqiang, Hu, Zhiyuan

Characterisation of Particle Number and Size from a DI SI Engine Operating on Hydrogen versus Gasoline: Operating Sensitivities and Filtration Effects

2026-01-0378

4/7/2026

Hydrogen Internal Combustion Engines (H₂ICEs) offer the potential for near-zero carbon emissions. However, while nitrogen oxide (NOₓ) emissions have been extensively studied, particulate emissions, specifically particle number (PN), which are widely attributed to in the literature to lubricant oil pyrolysis and exacerbated by hydrogen’s short quenching distance, remain less well understood. This study investigates exhaust-gas particle emission characteristics from a spark-ignition, single-cylinder research engine based on MAHLE Powertrain’s downsizing engine combustion system. The work was carried out at Brunel University of London and compares gasoline and hydrogen direct-injection strategies (central versus side injection) across a wide range of operating conditions, including variations in engine speed, load, air–fuel ratio (λ), rail pressure, and spark timing. While previous studies have investigated hydrogen particle formation mechanisms under isolated operating conditions, the combined influence of combustion strategy, mechanical engine condition, and exhaust filtration has not been systematically explored within a single experimental framework. This study characterises PN emissions and particle size distributions (PSDs) from a direct-injection spark-ignition research engine operating on hydrogen and gasoline under steady-state conditions. The effects of injection strategy (central versus side), air–fuel ratio (λ), rail pressure, and spark timing are examined, alongside a controlled comparison between a freshly overhauled engine and a mechanically worn configuration to assess sensitivity to oil-control condition. Particle measurements were performed using a fast-response differential mobility spectrometer equipped with a catalytic stripper to isolate solid particles, with results interpreted using SPN₁₀-equivalent metrics for comparative analysis. In addition, a series-production gasoline particulate filter (GPF) was evaluated under hydrogen operation to assess its ability to attenuate the ultrafine particles characteristic of H₂ICE exhaust. The results show that hydrogen combustion produces substantially lower engine-out PN than gasoline under comparable operating points, with particle size distributions strongly biased toward sub-23 nm diameters. PN emissions under hydrogen operation exhibit sensitivity to injection targeting, mixture strength, rail pressure, and engine mechanical condition, consistent with literature linking lubricant oil ingress and near-wall combustion behaviour to hydrogen PN formation. The GPF demonstrated measurable PN reduction under hydrogen operation in the single-cylinder, steady-state configuration examined Overall, this work provides an internally consistent dataset linking hydrogen combustion behaviour, engine mechanical condition, and injection strategy to PN emissions and filtration response under steady-state conditions. The findings are intended to inform calibration development, hardware design, and future certification-grade studies, rather than to demonstrate regulatory compliance.

Harrington, Anthony, Zaman, Zayne, Nickolaus, Chris, Zhao, Hua, Wang, Xinyan, Hall, Jonathan

Physics-Based Simulation for Sustainable Fuels Part 2.1: Inter-Ring Pressure Measurements and 2D/3D Ring Dynamics Analysis across Multiple Engine Platforms – Light Vehicle

2026-01-0281

4/7/2026

The growing demand for sustainable mobility and transportation is accelerating the adoption of alternative fuels, particularly hydrogen, in internal combustion engines. The first part of this publication series highlights the significance of 2D simulation as a crucial and computationally efficient tool for the precise development of hydrogen Power Cylinder Units. This approach demonstrates predictive capability proofed through engine tests, achieving a reduction in lube oil consumption by 5 g/h during high-load operations, alongside a 28% decrease in blow-by and an 11% reduction in hydrogen flow to the crankcase. To provide deeper insights into the complexities identified in Part 1, this study employs inter-ring pressure measurements across various engine types and configurations, including light vehicles, heavy-duty trucks, and large-bore applications, covering a broad range of engine displacements from 2 to almost 100 liters. This investigation in Part 2.1 focuses on understanding the cyclic variations and mechanisms that lead to oil emissions during low-load operations at a light vehicle, while Part 2.2 focuses on upper compression ring instabilities, cyclic variation in a heavy-duty engine and as well as the factors contributing to irregular combustion phenomena within a large bore engine. Complementing predictive 2D simulations and inter-ring pressure measurements, targeted 3D analyses are performed for capturing three-dimensional effects such as bore distortion and ring conformability. These analyses yield valuable insights into oil transport mechanisms that can contribute to irregular combustion. Part 3 of this publication series will concentrate on 3D oil transport simulations and optimization, including predictions of absolute lube oil consumption ranges of the hydrogen engine discussed in Part 1, while building on the valuable insights gained from the in-depth investigation of Part 2.

Moreira, Rui, Köser, Philipp, Rösch, Hannes, Ehnis, Holger

Emission and Combustion Characteristics of a Hydrogen Direct-Injection Spark Ignition Engine Using EGR

2026-01-0325

4/7/2026

This study experimentally investigates the combined effects of exhaust gas recirculation (EGR) and injection timing on the combustion and emission characteristics of a hydrogen direct injection engine. A single-cylinder 395 cc research engine was used, with injection timing varied from 60° to 180° BTDC and EGR rates from 0% to 30%. In-cylinder pressure, apparent heat release rate (AHRR), NOx, and unburned hydrogen concentrations were measured to analyze the influence of mixture formation and dilution on engine performance. Under non-EGR conditions, retarding the injection timing promoted mixture stratification, resulting in faster flame propagation and shorter combustion duration. However, localized high-temperature regions increased NOx formation, while incomplete combustion in lean or rich zones elevated unburned hydrogen emissions. When EGR was introduced, both ignition delay and combustion duration increased due to reduced oxygen concentration and thermal dilution. Nevertheless, the net indicated mean effective pressure (nIMEP) and indicated thermal efficiency (ITE) decreased by less than 1.6% and 1%, respectively, demonstrating that hydrogen’s fast combustion characteristics compensated for the reactivity loss. As the EGR rate increased, the formation of NOx and the emission of unburned hydrogen showed noticeable changes. At 30% EGR, NOx emissions decreased by up to 76% compared to the non-EGR baseline while maintaining stable combustion. However, excessive EGR resulted in increased unburned hydrogen emissions. These findings confirm that, with a properly optimized EGR rate, EGR is a more effective strategy than injection timing control for NOx reduction, achieving significant reduction with minimal efficiency penalty, and providing design insights for practical hydrogen-fueled engines.

Yang, Heetae, Ki, Youngmin, Kim, Jungho Justin, Kim, Jinsu, Bae, Choongsik, Hwang, Joonsik

Investigation of CDI and TCI Ignition Characteristics for Lean Hydrogen-Air Mixtures in a Constant Volume Combustion Chamber

2026-01-0327

4/7/2026

The discharge characteristics of ignition systems critically influence flame kernel formation and ignition stability under lean-burn conditions. This study experimentally compares a transistor coil ignition (TCI) and a capacitor discharge ignition (CDI) system in a constant-volume combustion chamber using hydrogen–air mixtures. The electrical behavior of both systems was first characterized through synchronized measurements of voltage, current, and high-speed imaging under various operating conditions with a resistive spark plug. The CDI system exhibited high-current (≈750 mA), short-duration (≈250 μs) discharges with strong instantaneous power but limited total spark-gap energy (≈5 mJ), while the TCI system produced lower-current, longer-duration (≈3 ms) discharges with higher cumulative energy (≈30 mJ). Flow-field tests revealed that the TCI discharge duration and energy release were strongly influenced by airflow, whereas CDI discharge behavior remained largely unchanged at flow velocities around 20 m/s. Ignition experiments with lean H₂–air mixtures (λ = 2.5–4.0) demonstrated that both systems can reliably ignite the mixture under quiescent and moderate-flow conditions, but the CDI system failed to sustain ignition near the lean limit. The results highlight the distinct energy-transfer mechanisms of the two ignition concepts and provide guidance for optimizing ignition design in future hydrogen internal combustion engines.

Cong, Binghao, Jin, Long, Yu, Xiao, Zhou, Qing, Tjong, Jimi, Zheng, Ming

Experimental Study of Entrainment by Hydrogen-Like Impinging Jets of Various Types in a Confined Compartment

03-19-01-0006

2/9/2026

Recent literature has highlighted significant heat transfer losses and elevated particle formation in direct-injection hydrogen engines, particularly when compared to hydrocarbon fuels such as methane. These challenges are attributed to hydrogen’s unique physicochemical properties, notably its short flame quenching distance and high diffusivity, as well as the interaction between the hydrogen jet and lubricated cylinder surfaces, which promotes lubricant entrainment into the combustion chamber. Consequently, a fundamental understanding of these entrainment mechanisms is a prerequisite for developing engineering strategies to enhance thermal efficiency and mitigate particle formation. The reported study investigates gaseous jet–air interaction in a confined volume to elucidate the influence of injector geometry on jet propagation and air entrainment. Three distinct jet configurations were examined: the wide hollow-cone, the narrow hollow-cone, and the round jets. The jet evolution and propagation were recorded using the Schlieren optical imaging technique for various pressure ratio values. The results indicate that for the wide hollow-cone jet, impingement on the vertical wall of the confined space is decoupled from horizontal surface impingement. Furthermore, this configuration yields a higher total entrained mass compared to narrow hollow-cone and round jets, under identical injected mass and pressure ratios. A notable finding is the inverse correlation between injection pressure and entrained volume for a fixed injected mass. Consequently, this study proposes new quantitative metrics for evaluating mixture preparation in direct-injection internal combustion engines.

Ben David Holtzer, Ben Binyamin, Tartakovsky, Leonid

Increasing the Efficiency of Hydrogen Direct Injection Internal Combustion Engines through the Use of Miller Cycles and Water Injection

03-19-01-0001

1/31/2026

Hydrogen-fueled reciprocating engines typically feature reasonable efficiencies and low engine-out emissions but low power density, compromising their utility and economics. Previous hydrogen engine research has found efficiency and anti-knock benefits when using either Miller cycles or water injection. This article therefore studies, for the first time, a directly injected (DI), spark-ignited, heavy-duty, turbocharged and hydrogen-fueled engine operated with both Miller cycles and water injection. Miller cycles, with either early or late intake valve closure, and water injection combine to achieve high engine efficiencies approaching 50%, which is significantly higher than the same engine with standard valve timing. The increased susceptibility of hydrogen autoignition in these Miller cycles is overcome by water injection, which simultaneously increases the charge density, counteracting both lean-burn hydrogen’s and Miller cycles’ commonly observed power loss. This demonstrates that the combination of DI, Miller cycles, and water injection is a pathway toward highly efficient, low-emission, hydrogen-fueled engines with power densities that are comparable to conventional engines.

Mortimer, Joel, Poursadegh, Farzad, Brear, Michael, Yang, Yi

Total Cost of Ownership Analysis of Fuel Cell and Hydrogen-Powered Commercial Vehicles for Cost Competitiveness with ICE and BEV

2026-26-0254

1/16/2026

Worldwide, the automotive industry is pivoting towards electrification and zero-emission vehicles (ZEV) to address greenhouse gas emissions and to meet net-zero emission goals. Although pure electric vehicles with rechargeable high-voltage batteries seem to be the most popular choice to achieve climate goals, hydrogen-powered vehicles are also seen by many as a viable technology to clean up the transportation sector. Hydrogen fuel cells and fuel cell-powered vehicles have been in development for a long time, and hydrogen internal combustion engines (ICE) have seen rapid development in the past few years. While the technological feasibility of hydrogen fuel cells and H2 ICE is being proven, the mass adoption of these technologies depends, along with other factors such as hydrogen infrastructure, upon financial feasibility as well. This paper presents a systematic analysis of the total cost of ownership (TCO) of hydrogen-powered vehicles, especially fuel cell electric vehicles. Different commercial vehicle categories are analysed to assess the vehicle classes and use cases where hydrogen fuel cell-powered vehicles can be a cost-effective alternative to conventional ICE and battery electric vehicles (BEV). The analysis also determines the factors that contribute most to TCO, which will help identify the areas that require improvement/development or policy support to make fuel cells and hydrogen power more widespread. The paper also analyses the sensitivity of TCO to different cost factors, such as hydrogen cost, which helps in establishing cost targets to make hydrogen-powered vehicles a cost-effective solution in the transition to zero-emission transportation. Finally, different market trends are analysed to predict the timelines in which fuel cell-powered vehicles can become cost-competitive with ICE and BEV.

Jacob, Joe, Chougule, Abhijeet

Establishing a High-Pressure Direct Injection Hydrogen Engine Test Facility with Integrated Ammonia Fuel Capability: Technical Considerations, Safety Framework, and Best Practices

2026-26-0267

1/16/2026

The transition toward zero-carbon propulsion technologies has highlighted the urgent need for specialized test infrastructure to support hydrogen and alternative fuel research. This paper presents the conceptualization, design, and operation of a High-Pressure Direct Injection (HPDI) Hydrogen Internal Combustion Engine (H2 ICE) test facility with integrated ammonia fuel testing capability, marking a significant advancement in India’s sustainable automotive research efforts. Drawing from practical experience, it outlines crucial technical specifications, safety protocols, and best practices for establishing robust, adaptable, and secure testing environments. Addressing the industry’s need for dedicated infrastructure, it is engineered for adaptability across various engine types including heavy-duty, light-duty, and multi-utility vehicles while aligning with global technical standards. Key technical considerations include a transient dynamometer with an advanced automation system for precise control of both hydrogen and ammonia test cycles. Emission measurement systems such as hydrogen analyzer, ammonia-specific FTIR, particle number counter, and particle size distribution analyzer, are essential for analyzing regulated and unregulated emissions that are critical to sustainable fuel development. The hydrogen fuel storage and distribution system support up to 500 bar pressure, incorporating certified components. Three distinct supply lines operating at 350 bar (for HPDI), 100 bar (for Low Pressure Direct Injection), and 20 bar (for Port Fuel Injection) to accommodate diverse engine configurations. A separate ammonia delivery system ensures dual-fuel testing while addressing its specific chemical and safety needs. Safety remains a cornerstone of the facility's design due to hydrogen’s flammability and ammonia’s toxicity. Essential measures include a high-capacity ventilation, ATEX-rated electricals, real-time gas detection, inert-gas fire suppression, remote monitoring using CCTV, thermal imaging and acoustic sensors. The facility serves as a benchmark for hydrogen and ammonia ICE research in emerging markets, providing practical insights, and technical recommendations and guidance for aligned infrastructure development in support of a zero-carbon mobility future.

Dhyani, Vipin, Kurien, Caneon, Subramanian, Balaji, Khandai, Chinmayananda, Muralidharan, M

3D CFD Simulation Methodology for Safe and Efficient Hydrogen Refueling for Hydrogen Internal Combustion Engines

2026-26-0252

1/16/2026

As conventional fossil fuels are on the verge of depletion, the demand of alternative fuel has intensified. Among these, Hydrogen offers higher energy output per unit weight compared to conventional fuels, high octane number, and compatibility with Internal combustion engines (ICE). However, the volatility of hydrogen (H2) presents challenges, particularly during the refueling process, where uncontrolled temperature rise occurs because of negative Joule-Thomson (JT) effect. This brings an alarming bell for the safety of fueling stations, vehicles, and mankind. This paper investigates the physics involved in hydrogen tank filling, focusing on maintaining the hydrogen gas temperature below 85 °C during the process. A 3D Computational Fluid Dynamics (CFD) analysis was performed to model the temperature and pressure behavior of hydrogen during filling. The study provides insights into the optimal fill rates, temperature distribution, and the evolution of peak temperature locations inside the tank, contributing as a critical dataset for safe and efficient hydrogen refueling strategies. This study is done using two simulation software - ANSYS Fluent 2024R1 and Simerics 6.0.0. The results from both the software show strong agreement, while Simerics demonstrated a significant computational advantage with runtimes as compared to Ansys Fluent. Additionally, a mesh and time-step sensitivity study were conducted to ensure the accuracy and stability of simulations.

Khanna, Gourav, Veerbhadra, Swati, Sahu, Abhay Kumar

Performance and Emission Characteristics of a Lean-Boosted Direct Injection Hydrogen Combustion System for Retrofitting Heavy Duty Diesel Engines

2026-26-0268

1/16/2026

To address the imperative for decarbonizing the heavy-duty transport sector and advancing sustainable energy solutions, this paper presents a novel lean-boosted Direct Injection (DI) Hydrogen Internal Combustion Engine (H2 ICE) combustion system. This system is developed to retrofit existing flat-deck Diesel engines, offering a viable pathway towards drastically reduced emissions. Building on consolidated expertise from prior production-oriented Port Fuel Injection H2 engine development (DUMAREY 6.6ℓ V8), this research focuses on leveraging the distinct advantages of DI for hydrogen. An experimental assessment, supported by 1D and 3D-CFD analyses, demonstrates the system's capability to achieve highly efficient operation in Spark Ignition (SI) mode under ultra-lean and EGR-diluted conditions. The study confirms the elimination of combustion anomalies such as backfiring, pre-ignition, and knock, while achieving ultra-low engine-out NOx emissions and near-zero CO2, HC, CO, and PM. The authors discuss the optimization of key combustion drivers and the beneficial effects of dilution strategies. The findings reveal the significant potential of this DI H2 system, particularly when applied to the swirling cylinder head designs typical of common Diesel engines, to facilitate a rapid and cost-effective transition to cleaner freight mobility. Additionally, a specific flat-deck based tumble motion design has been investigated as a mixing improver versus swirl design, showing further margin for enhancing efficiency and effectiveness of the combustion process.

Gessaroli, Davide, Golisano, Roberto, Pesce, Francesco, Boretto, Gianmarco, Accurso, Francesco

Experimental Evaluation of Energy and Exergy of Hydrogen, CNG and Gasoline Fuelled High-Speed Spark Ignition Engine

2026-26-0258

1/16/2026

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

Comparitive Study of Hydrogen Internal Combustion Engine Performance for Port Fuel Injected and Direct Injected Technology Routes using 1D Simulation

2026-26-0250

1/16/2026

Hydrogen Internal Combustion Engine (HICE) has the promise of zero carbon solution for the mobility industry. The key beneficiary would be the medium and heavy-duty segment of transportation which are likely to adapt the battery electric or fuel cell electric solution in longer term. This particular segment of engines need high low end torque, peak torque and rated power which cannot be compromised. Additionally, a competitive thermal efficiency w.r.t diesel engines would be advantageous. Direct Injection (DI) of hydrogen gives higher specific power and thermal efficiency as compared to Port Fuel Injection (PFI). This study focuses on the performance characteristics of these technology routes to aid in the HICE development process. Current work involves the use of 1-D thermodynamic simulation using GT-SUITE for modeling the performance of HICE. Both predictive and non-predictive methodologies of modeling the combustion were employed. Initially, the model validation of the PFI engine model was carried out with the HICE baseline experimental data for a heavy-duty commercial truck engine. Subsequently, a DI engine model was created and with similar combustion modeling methodology, the performance assessment was carried out. The study presents all aspects of full throttle performance of both the PFI and DI technology routes for HICE. The simulation results show that DI methodology is advantageous as it gives a minimum of 3 to 5% increased torque as compared to PFI route with the same turbocharging system. Using a DI methodology helps to enhance the volumetric efficiency of the engine unlike PFI where the hydrogen gas displaces air in the intake system. DI strategy is also less susceptible to knocking combustion. Various combustion behavior insights namely, the combustion duration, mass burned fraction, peak combustion pressures and temperatures are also obtained as a part of the study.

Parthiban R, Varun, Karthikeyan, K R, Narayana Reddy, J, Paramasivam, Prakash, Manjunath, M, Kumar D, Kishore, N R, Varatharaj, Suresh, K, G, Yogesh Bolar, Sadagopan, Krishnan, Pandey, Sunil Kumar

Design Optimization of the Vanity Cover for H ₂ Concentration Management

2026-26-0263

1/16/2026

The integration of hydrogen (H2) as a fuel source in internal combustion engines (ICE) necessitates stringent design measures to mitigate leakage risks and ensure operational safety. This study focuses on the design optimization of vanity cover for hydrogen engines. Computational fluid dynamics (CFD) analysis is carried out to assess and control hydrogen leakage through fuel rail connections, injector interfaces and associated high pressure fuel system components. Detailed modelling of hydrogen flow behavior, diffusion characteristics of leaked hydrogen are simulated for worst case scenarios. Design iterations targeted improvement in ventilation pathways, strategic placement of vent holes, and internal flow management to minimize localized hydrogen buildup. The final design achieved hydrogen concentration, which was less than 4%. This paper validates the critical role of CFD driven design methodology in proactively identifying leakage risks and optimizing component geometries for enhanced safety and regulatory compliance without compromising structural integrity or manufacturability.

Veerbhadra, Swati Ashvinkumar, Sahu, Abhay Kumar, Singh, Rahul

Comprehensive Engine Testing Methodologies for Hydrogen Internal Combustion Engine Validation with Combustion & Performance Evaluation Techniques

2026-26-0256

1/16/2026

Validation of hydrogen-fuelled internal combustion engine (H2 ICE) is critical to assess its feasibility as sustainable transportation with zero carbon emissions. This experimental analysis conducted on Ashok Leyland’s 6cylinder 2V engine to evaluate the engine performance & durability with hydrogen fuel. Combustion behaviour of hydrogen ICE needs to be closely monitored during continuous operation of validation testing, due to its unique properties compared to other conventional fuels. During engine run, a pre-ignition source can cause knock event leading to instant failure of critical parts like piston assembly, spark plug, liner, valves & cylinder head. Also, hotspots inside IMF leads to backfire affecting the air intake & fuel injection assembly. This study emphasizes the significance of precise instrumentation of thermocouples across engine on cylinder head, intake manifold & exhaust manifold, to detect performance detoriation and combustion abnormalities causing knocking & backfire. Crankcase ventilation system design plays a critical role in evacuating the blowby gas from engine block. This paper explains methodology to measure the moisture condensation from blowby gas, as it leads to oil emulsification. Experimental data shows variation in inlet manifold air temperature directly impacts engine power as H2 ICE operates at higher stoichiometric ratio. Increase in air intake temperature from turbo compressor out is a result of barometric temperature and pressure variation. This measurement is critical to understand the engine performance variation in real-time operating condition. Hence validation of H2 ICE necessitates a specialized instrumentation during testing to monitor the performance parameters and hardware detoriation. This research provides critical insights into the procedural adaptations required for H2 ICE testing and validation by integrating frugal instrumentation with experimental analysis. This study offers a robust framework for assessing engine performance, reducing operational risks, and ensuring test results reliability. These findings contribute to the design & development of hydrogen-fuelled engines, facilitating their adoption as a sustainable alternative for transportation while addressing durability, emissions, and regulatory compliance challenges.

Vasudevan, Sindhuja, J, Narayana Reddy, Bolar, Yogesh Ganesh, Pandey, Sunil, N, Harish, N R, Varatharaj, Karthikeyan, K, Kumar D, Kishore

Controls Solutions for Commercial Hydrogen Engines

2026-26-0112

1/16/2026

India’s commitment to carbon neutrality is significantly shaping the future architecture of commercial vehicle powertrains. While the use of CO₂-free technologies such as battery-electric drivetrains has already been successfully demonstrated across various applications, challenges related to limited range and the lack of high-power charging infrastructure continue to hinder widespread adoption, particularly for productivity-critical commercial vehicles. This has shifted the spotlight toward sustainable fuels, which offer the advantage of fast refueling times. Among these, hydrogen internal combustion engines (H₂ ICE) have gained increasing attention in recent years. In regions such as the European Union, the primary motivation for hydrogen is CO₂ reduction. In contrast, for markets like India, hydrogen also presents a strategic opportunity for reducing dependency on fossil fuel imports. Over the past four years, multiple performance and emission development projects across various H₂ ICE configurations have been carried out. A key enabler in these projects has been AVL’s Rapid Prototyping Engine Management System (RPEMS), featuring mature application software (ASW) designed to support port fuel injection (PFI, MPI), direct injection (DI), and high-pressure direct injection (HPDI) with diesel pilot. The system supports both steady-state and transient operation and includes functionality for exhaust aftertreatment control, such as single or dual-dosing SCR systems. For series production projects, the industry emphasizes compatibility with existing engine control strategies. Particularly for OEMs with in-house controls development, extending current functionalities to include H₂ ICE operation is more attractive than developing entirely new software from scratch. To validate this, AVL has adapted both its diesel-based (quality-controlled) and gas-based (quantity-controlled) software architectures to manage various hydrogen combustion strategies. Hybrid configurations are also possible, where standard EMS handles torque and air path control, while RPEMS manages hydrogen injection, ignition, and lambda control, enabling early-stage concept evaluation on engine testbeds or in vehicles. Additionally, robust detection and response to irregular combustion events such as knocking, misfire, and early or late pre-ignition, sometimes accompanied by backfire, are essential for ensuring engine protection and durability. This paper presents testbed results comparing diesel-based and gas-based control strategies applied to advanced H₂ ICE models. It also discusses approaches for irregular combustion diagnostics and the corresponding protective control measures.

Arnberger, Anton, Danninger, Alois, Mannsberger, Stefan, Breitegger, Bernhard

Analysis of Indian Patent Landscape on Alternative Fuels with a Focus on Hydrogen Fuel Cells and Hydrogen Internal Combustion Engines

2026-26-0262

1/16/2026

This paper presents an analysis of the Indian patent landscape concerning alternative fuels, with a specific focus on hydrogen fuel cells and hydrogen internal combustion engines (H2 ICEs). The study aims to provide insights into the innovation trends, key players, white spaces and technological advancements, in this evolving sector within the Indian context. The study is based on the granted patents and disclosures in the said area, and also focuses on the key problems and solutions. Based on a review of patent publications from January 2024 to March 2025, it was observed that a significant number of patent records pertain to the broader domain of hydrogen internal combustion engine disclosures. Specifically, 540 extended families patent publications were screened focusing on hydrogen internal combustion engine as a domain of disclosure. Further analysis revealed that greater 75 % of applicants were from the industry sector, indicating a strong commercial interest in these technologies. Key OEM players in the mobility space, Tier-I and Tier-II technology solution providers are prominent applicants in the said technology, particularly in areas like fuel systems, storage and material compatibilities The study engages key search strategies around the technical domains in area of hydrogen as an alternative fuel with respect to IC engines and fuel cells, which will enable the technical diaspora around the research and disclosures in this area. The technical teams would also get a learned view on the problems and solutions associated with these technologies.

Nikam, Mahesh Suresh, Sutavane, Ila, V, Ajay, Aghav, Yogesh

Optimizing Hydrogen Engine Performance a Comparative Study of Lean & Stoichiometric Calibration Approach

2026-26-0261

1/16/2026

Hydrogen combustion in internal combustion engines offers numerous advantages, such as zero CO2 emissions and high flame speed, which make it a promising alternative fuel for green vehicle solutions. In order to maximize the engine performance with hydrogen, however, meticulous calibration of the air-fuel mixture must be performed, particularly when lean and stoichiometric combustion conditions are considered. Lean burning, i.e., excess air, offers better thermal efficiency and lower NOx emissions but can cause lower engine power and combustion instability. Stoichiometric combustion, however, ensures complete combustion of the fuel-air mixture, but at the cost of higher combustion temperatures and consequently, high NOx emissions. Calibration strategies for hydrogen engines are presented in this paper by comparing the lean and stoichiometric strategies and their implications on engine power output, efficiency, and emissions. Test data from several hydrogen engine configurations demonstrate that lean burn with EGR addition can be employed to minimize NOx emissions at the expense of tight engine stability and power control. On the other hand, stoichiometric operation yields more power but with the requirement for complex emission control systems. The compromises between these calibration strategies are presented in the paper and recommendations are provided on optimizing the performance of hydrogen engines for different operating conditions.

Jadhav, Ajinkya, Bandyopadhyay, Debjyoti, Sutar, Prasanna S, Sonawane, Shailesh Balkrishna, Rairikar, Sandeep D, Thipse, Sukrut S

Data-Driven Modeling for Emission Prediction and ATS Performance Benchmarking for Hydrogen and Diesel ICE Applications

2026-26-0386

1/16/2026

This study presents a comprehensive methodology for benchmarking hydrogen and diesel internal combustion Engines, with emphasis on virtual Real-Drive Emission (RDE) test procedures for diesel and hydrogen application. Emission profiles for legal cycles and RDE scenarios are accurately predicted through integration and development of Artificial Neural Networks (ANN) based on Long Short-Term Memory (LSTM) models. Virtual evaluations of Selective Catalytic Reduction (SCR) system performance, Diesel Exhaust Fluid (DEF) dosing accuracy, and exhaust temperature dynamics enabled by integrated data pipelines and physics-based modeling are also explored for holistic prediction of output. Across models, validation demonstrates good prediction accuracy including temperature (R2 > 0.94, RMS error < 25°C), air flow (92% accuracy, RMSE = 28 kg/h), upstream NOx (93% accuracy, RMSE < 10 mg/s), and SCR (TP NOx accuracy = 91.82%, dosing accuracy = 87.73%). This approach has the potential to offer significant reduction in the need of extensive on-road driving tests, as the model provides capability to emulate the same, thereby lowering development costs and supporting OEMs in meeting stringent emission standards through efficient benchmarking of Aftertreatment systems (ATS).

Shah, Jash Vipin, S, Manoj Kumar, Ratnaparkhi, Aditya, H, Shivaprakash

Computational Study of Hydrogen based SCR Technology as an Alternative to Urea SCR in Hydrogen Fueled Engine

2026-26-0213

1/16/2026

Air pollution from vehicle exhaust emissions is a growing issue in major cities around the world. Hydrogen is a clean and carbon-free fuel that presents a promising alternative to the fossil fuels. However, despite its environmental advantages, hydrogen internal combustion engines still produce some nitrogen oxides as a by-product due to high combustion temperatures. This study investigates the effectiveness of current exhaust after-treatment technologies designed to reduce NOx emissions in hydrogen-powered engines. A comparative analysis is conducted between the conventional urea-based selective catalytic reduction used in diesel engines and emerging hydrogen-based selective catalytic reduction technologies for hydrogen engines. The analysis is performed using CFD simulation in ANSYS Fluent, focusing on NOx reduction efficiency and other operational parameters. The results provide valuable insights into the feasibility and effectiveness of hydrogen SCR in achieving reduced NOx emissions, and this technology also eliminates the current urea storage and dosing arrangement, as vehicle-on-board available hydrogen can be used for NOx reduction in hydrogen-based SCR technology.

Kashyap, Keshav, Khandagale, Anup, Petale, Mahendra

Impact of Hydrogen Electrification on Transmission Systems for Heavy-Duty Vehicles

2025-36-0178

12/18/2025

Powertrain architecture is being reshaped by the electrification of heavy-duty military vehicles using hydrogen fuel cell technology, particularly in transmission systems. Unlike conventional internal combustion engines, hydrogen fuel cell electric vehicles (FCEVs) typically use single-speed or direct-drive configurations due to the high torque of electric motors. This paper examines the impact of hydrogen electrification on military vehicle transmissions, focusing on armored multi-role models such as the VBMT-LSR, Guarani, and Leopard 1A5 of the Brazilian Army. The study compares traditional gearboxes with alternative solutions optimized for fuel cells, analyzing the trade-offs in efficiency, durability, and operational adaptability. Additionally, it explores adaptations required for hydrogen internal combustion engines (H2-ICEs), considering their distinct characteristics and demands. The study employs a three-step validation methodology combining computational simulations, technical data analysis, and case studies of military vehicles. MATLAB and similar tools are used to assess efficiency, durability, and torque response under field conditions. Next, specifications from existing military vehicles in the Brazilian Army are analyzed to evaluate the feasibility of hydrogen powertrains compared to diesel-based solutions. Finally, the study examines international military projects that have already integrated hydrogen or electrification, such as GM SURUS and Rheinmetall Mission Master, drawing insights into the applicability of these concepts in the Brazilian military context. This research enhances the understanding of hydrogen-powered transmissions, contributing to the future development of more sustainable powertrain solutions and thus supporting the adaptation of military fleets to alternative energy sources and accelerating the adoption of hydrogen-based mobility in defense applications.

Biêng, Ethan Lê Quang, Pontes, Guilherme Ayroso, Conrado, Guilherme Barreto Rollemberg, Lopes, Elias Dias Rossi, Rodrigues, Gustavo Simão

Artificial Neural Network-Based Performance and Emission Prediction for Hydrogen-Combustion Multicylinder Engines

2025-36-0237

12/18/2025

In response to the pressing need to reduce greenhouse gas emissions from the transportation sector, hydrogen-fueled internal combustion engines (H2ICEs) have emerged as a promising alternative to conventional fossil-fueled powertrains. However, optimizing H2ICEs presents challenges in balancing performance with emissions, particularly in nitrogen oxide (NOx) formation This study proposes a data-driven methodology using an artificial neural network (ANN) to predict key emission and performance metrics: NOx emissions, brake mean effective pressure (BMEP), brake specific fuel consumption (BSFC), brake power, and brake thermal efficiency, based solely on engine operational parameters. Experimental data were collected from a three-cylinder Ford EcoBoost engine under varying conditions of intake pressure, spark timing, air-fuel ratio, engine speed, and valve timing. Feature selection was performed using the Spearman correlation coefficient, identifying engine speed, start of injection angle (SOI), air-fuel ratio (λ), and intake pressure as the most important input variables. Bayesian optimization was employed to tune the ANN’s hyperparameters, resulting in a network architecture with a single hidden layer consisting of 10 neurons using the tanh activation function, optimized with the Adam optimizer at a learning rate of 0.01. The final ANN model exhibited satisfactory predictive performance, achieving correlation coefficients greater than 0.97 for most outputs and exceeding 0.95 across all predicted variables. These results demonstrate that the proposed ANN effectively captures the nonlinear behavior of hydrogen-fueled engines and offers a valuable tool for reducing the experimental burden in engine calibration and development, thereby supporting the advancement of hydrogen-powered mobility solutions.

Pasa, Bruno Roberto, Silveira, Juliano Pereira, Fagundez, Jean Lucca Souza, Lanzanova, Thompson Diórdinis Metzka, Martins, Mario Eduardo Santos, Salau, Nina Paula Gonçalves

Investigation of Active Pre-Chamber Ignition on an Optically Accessible Ultra-Lean DI Hydrogen Engine

2025-01-0524

11/25/2025

Hydrogen is a promising alternative to conventional fuels for decarbonizing the commercial vehicle sector due to its carbon-free nature. This study investigates the ignition and flame propagation characteristics of hydrogen in a 2-liter single-cylinder optical research engine representative of the commercial vehicle sector. The main objective was to enable high power density operation while minimizing NOx emissions. For that, ultra-lean combustion was employed to lower in-cylinder temperatures, addressing the challenge of NOx formation. To counteract delayed and unstable combustion under lean conditions, an active pre-chamber ignition system was implemented. It uses a gas-purged pre-chamber with separate hydrogen injection and spark plug ignition. Turbulent hot gas jets from the pre-chamber ignite the fresh mixture in the main combustion chamber, enabling faster and more stable ignition compared to conventional spark plugs. Additionally, the low volumetric energy density of hydrogen, which limits performance in port fuel injection due to air displacement, was addressed through direct hydrogen injection into the combustion chamber to increase the mixture heating value. High-speed imaging techniques, including Schlieren and OH chemiluminescence, were used alongside thermodynamic analysis to study combustion dynamics. Results demonstrate that the active pre-chamber ignition system achieved stable combustion at ultra-lean conditions (λ up to 4) without knocking phenomena. Essentially, NOx-free operation was possible for λ > 2.5. Pre-chamber conditions were found to influence performance trade-offs: richer mixtures enhanced stability and combustion speed, while leaner mixtures minimized NOx emissions. Comparative measurements with a standard spark plug showed that pre-chamber ignition leads to more stable and faster ignition, unlocking additional performance and efficiency potential. These findings demonstrate the viability of hydrogen as a carbon-neutral zero-emission fuel for commercial vehicle engines.

Borken, Philipp, Bill, Daniel, Link, Lukas, Dinkelacker, Friedrich, Hansen, Hauke

Evaluation of Advanced Powertrain Technologies for Large Agricultural Tractors: Insights on Energy Consumption and Life Cycle Environmental Impact

13-06-03-0025

11/21/2025

This study aims to assess how alternative electrified powertrain technologies affect energy use for agricultural tractors in the Autonomie simulation tool. The goal of this study is also to assess the feasibility and performance of hydrogen internal combustion engines as a suitable alternative for the agricultural tractor powertrains. The energy consumption and efficiencies of alternative powertrains and fuel options are analyzed and compared across a variety of duty cycles using modeling and simulation methodologies. The considered alternative powertrains are series, parallel, power-split hybrid electric, fuel cell, and battery electric powertrains. The alternative fuel and powertrains are evaluated for their energy efficiency as well as their potential to reduce greenhouse gas emissions and improve overall tractor performance in a variety of agricultural applications. Following a methodology developed by Argonne National Laboratory and Aramco Americas, the study applied prospective future technology scenarios to the agricultural sector. The simulation results suggest that battery electric powertrains and fuel cell electric powertrains offer long-term greenhouse gas reduction potential when combined with renewable energy production, while alternative powertrains with hydrogen engines can be considered as one of intermediate solutions that offer more practical and competitive operating costs while leveraging existing powertrain component manufacturing infrastructure. The results of this study provide insight into the benefits and challenges of integrating alternative fuel and alternative powertrain technologies into agricultural machinery and point the way toward more sustainable and energy-efficient agriculture.

Kim, Namdoo, Yan, Ziming, Vijayagopal, Ram, Jung, Jaekwang, He, Xin

Advanced Multi-Fidelity Simulation of Piston Oil Jet Cooling in High-Performance Engines

2025-32-0081

11/3/2025

The development of next-generation hydrogen-fueled engines introduces critical challenges related to thermal loads within the combustion chamber, particularly in high-performance applications. To address the extreme temperatures encountered, effective piston cooling strategies, such as oil jet impingement, are essential. Accurately predicting thermal stresses to prevent component failure is therefore crucial. However, numerical simulations often come with significant computational costs. This paper presents a comprehensive multi-fidelity modeling approach to predict the thermal behavior of pistons under these demanding conditions. The model integrates a simplified 3D thermal representation of the piston, a lumped-parameter mechanical model of the piston-liner assembly, and convective boundary conditions obtained at various levels of fidelity, from high-level Computational Fluid Dynamics (CFD) simulations to literature correlations. Additionally, the study examines the influence of different approaches to defining boundary conditions on the model’s predictive capability. Calibration of the model was achieved using experimental temperature measurements obtained by sampling residual surface hardness at 8 points on the piston crown after prolonged stationary operation at maximum power in a conventional naturally aspirated high-performance gasoline engine test case. The results demonstrate a strong correlation between experimental data and numerical predictions, validating the model's accuracy. Additionally, the study investigates the influence of piston crown thickness and the positioning of the cooling oil injection point on the maximum temperatures reached during operation. Findings reveal the critical role of both geometric design and cooling strategies in optimizing thermal performance. This work provides a robust, flexible, and affordable simulation framework for evaluating piston thermal behavior, contributing to the design of reliable engines capable of withstanding extreme thermal conditions.

Sassoli, Andrea, Romani, Luca, Ferrara, Giovanni, Paolicelli, Giovanni, Balduzzi, Francesco

Experimental Study of hCNG on Single Cylinder 395cc Spark Ignition Engine for Performance and Exhaust Emission

2025-32-0050

11/3/2025

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

Clarification of the Mechanism of Abnormal Combustion in Hydrogen Engines -Investigation of Abnormal Combustion Location by Visualization Measurement-

2025-32-0064

11/3/2025

Hydrogen internal combustion engines present a promising path towards carbon neutrality, yet their development is challenged by abnormal combustion phenomena like backfire and pre-ignition. These phenomena limit engine torque and reduce component reliability. This study is aimed to elucidate the mechanisms behind these phenomena in hydrogen internal combustion engines. We utilized a multi-cylinder engine with optical access for direct high-speed imaging of in-cylinder processes to visualize backfire and pre-ignition. Initial analysis, combining visualization data with one-dimensional (1D) simulations, indicated that high temperatures of the ground electrode of the spark plug could be a key trigger factor for abnormal combustion. To investigate this hypothesis, the surface temperature of the ground electrode was measured under firing conditions using a two-color thermometry system. The measurements revealed that the electrode temperature exceeded the compressed gas temperature near Top Dead Center (TDC). This finding suggests the possibility of hot surface ignition initiated by heat transfer from the hot electrode surface to the hydrogen-air mixture prior to the spark event. To mitigate this, the ground electrode material was replaced with a material with higher thermal conductivity to improve heat dissipation. Subsequent tests on the multi-cylinder engine confirmed the effectiveness of this modification, and the spark plug with the high-conductivity ground electrode showed a significant reduction in pre-ignition frequency. These results establish that the ground electrode temperature is one of the factors contributing to abnormal combustion, particularly pre-ignition, in hydrogen engines. This study provides valuable insights into mitigating abnormal combustion in hydrogen internal combustion engines, advancing their development towards more reliable and efficient operation, and supporting the broader goal of carbon neutrality.

Muramatsu, Keiji, Tokuhara, Satoshi, Kadu, Pravin, Yoshimura, Kei, Nakama, Kenjiro

Effect of In-Cylinder Hydrogen Mixture Formation on Hydrogen Combustion

2025-32-0065

11/3/2025

Global efforts to mitigate climate change include ambitious long-term strategies by countries to achieve net-zero greenhouse gas emissions by 2050. The automotive sector is exploring carbon-free powertrains, with hydrogen emerging as a key technology. Its zero-emission potential positions it for widespread adoption in power generation, transportation, and industry. Hydrogen engines, particularly direct injection engines offering high power and efficiency, are gaining traction due to their adaptability using existing engine components. However, in a hydrogen direct injection engine, achieving proper mixing of hydrogen and air in the cylinder is challenging, making in-cylinder mixture formation a crucial factor for ensuring stable combustion. To predict hydrogen mixture formation in the cylinder, we conducted a Schlieren visualization experiment of the hydrogen jet. Based on the results, a detailed hydrogen jet model for the direct injection injector was developed. This model was then integrated into the in-cylinder analysis, allowing an investigation into the impact of injection timing on hydrogen combustion. Furthermore, hydrogen combustion experiments were carried out using a single-cylinder hydrogen direct injection engine, and the accuracy of the in-cylinder analysis results was validated.

Hisano, Atsushi, Saitou, Masahito, Sakurai, Yota, Ichi, Satoaki

Development of the Hydrogen Fueled Internal Combustion Engine for Off-Road Applications

2025-32-0066

11/3/2025

This paper focuses on the potential application of hydrogen fueled internal combustion engine (HICE) in the off-road market, examining HICE based on a diesel engine. In the transition to HICE, priority was given to compatibility with existing systems, minimizing changes from the base engine. By adopting a PFI (Port Fuel Injection) method for fuel injection, low-pressure hydrogen supply was achieved. To address the issue of backfire associated with PFI, optimization of injection pressure using a variable pressure control valve, along with adjustments to valve timing and injection timing, was implemented to suppress backflow of residual gases into the intake system and minimize hydrogen retention. Regarding pre-ignition, in addition to suppressing hotspots, the relationship between the homogenization of the air-fuel mixture and NOx emissions was examined, revealing a correlation. This engine was mounted on a generator, and efforts were made to improve the important characteristic of responsiveness in generators. As a result, it was confirmed that the responsiveness is comparable to that of existing gas engine generators.

Shiraishi, Kentaro, Kishi, Shinji, Kato, Daichi, Mitamura, Kenta, Murakami, Kei, Mikuni, Yusuke

Analysis of Flame Propagation Characteristics in a Hydrogen Engine using an Optically Accessible Engine

2025-32-0061

11/3/2025

This study focused on the effects of hydrogen on the flame propagation characteristics and combustion characteristics of a small spark-ignition engine. The combustion flame in the cylinder was observed using a side-valve engine that allowed optical access. The fundamental characteristics of hydrogen combustion were investigated based on combustion images photographed in the cylinder with a high-speed camera and measured cylinder pressure waveforms. Experiments were conducted under various ignition timings and equivalence ratios and comparisons were made with the characteristics of an existing hydrocarbon liquid fuel. The hydrogen flame was successfully photographed, although it has been regarded as being difficult to visualize, thus enabling calculation of the flame propagation speed. As a result, it was found that the flame propagation speed of hydrogen was much faster than that of the existing hydrocarbon fuel. On the other hand, it was difficult to photograph the hydrogen flame directly in the lean region. In future studies, it will be necessary to reduce the shooting speed or to conduct investigations based on spectroscopic measurements. Regarding hydrogen combustion, it was found that the combustible range of hydrogen was broad even when the experimental conditions were substantially varied. It was also found that the combustible period was much shorter than that of the existing hydrocarbon fuel. Misfiring and after-firing were observed in hydrogen combustion where the ignition timing was close to top dead center as well as under a lean condition. This confirmed that there are issues concerning hydrogen combustion stability under such conditions.

Arai, Yuto, Ueno, Takamori, Suda, Ryosuke, Sato, Ryoichi, Nakao, Yoshinori, Ninomiya, Yoshinari, Matsushita, Koichiro, Kamio, Tomohiko, Iijima, Akira

A Study of Knocking Characteristics in a Hydrogen SI Engine under High Compression Ratio

2025-32-0063

11/3/2025

This study investigated the knocking characteristics of a hydrogen spark ignition engine for the purpose of increasing efficiency and expanding the operating range. In recent years, research focused on carbon neutrality has been vigorously conducted, and hydrogen has attracted attention as a next-generation fuel for internal combustion engines (ICEs). The combustion characteristics of hydrogen are vastly from those of existing gasoline. It is essential to have a sufficient understanding of the combustion characteristics of hydrogen in order to develop next-generation ICEs designed to operate on hydrogen fuel. There are especially many aspects of the knocking mechanisms of hydrogen that are unclear. Consequently, those characteristics and mechanisms must be clarified for the purpose of expanding the operating range of hydrogen engines and enhancing their efficiency. In this study, experiments were conducted using a single-cylinder hydrogen engine that was operated at a high compression ratio of 17:1. High-intensity knocking was observed while operating the engine under various ignition timings and equivalence ratios. The knocking intensity and knocking mode characteristics were examined based on the observed knocking data.

Ishihara, Hiromasa, Kishibata, Shunsuke, Miyake, Shota, Iida, Tomoya, Kuwabara, Kenta, Yoshihara, Shintaro, Miyamoto, Sekai, Iijima, Akira

Transient Helium Jet Evolution Using High Speed Schlieren Imaging

2025-32-0057

11/3/2025

The accelerating global shift towards decarbonised energy systems has positioned hydrogen as a highly promising carbon-free fuel. This study comprehensively investigates the macroscopic characteristics and temporal evolution of vortex ring trailing helium jets, serving as a surrogate for hydrogen, injected into a quiescent ambient environment using high-speed Schlieren imaging. This research addresses critical insights into fuel-air mixing dynamics essential for optimising hydrogen direct injection (DI) internal combustion engines. Analysis of helium jet tip’s topology revealed a three-stage evolution from an initial pressure-insensitive phase, dominated by pressure wave structures, to a momentum-driven, vortex-dependent growth stage, then to a fully developed stage. Specifically, the lower-pressure cases showed increased Kelvin-Helmholtz instability and distinct head vortex pinch-off at the final stage. Jet tip velocities transitioned from initial high, rapid pressure wave development speeds to a momentum-controlled phase, with lower-pressure jets exhibiting greater fluctuations and susceptibility to Kelvin-Helmholtz instabilities effects. Jet width growth initially mirrored across pressures due to vortex ring expansion before diverging into a turbulent mixing regime, notably displaying a transient width reduction as internal ring structures dissipated. The jet angle stabilised around 32°, with higher injection pressures resulting in slightly narrower angles due to enhanced axial momentum. Overall, jet area growth was significantly faster and larger at higher injection pressures, confirming their superior mixing potential. These findings provide crucial insights into the interplay of injection parameters, vortex dynamics, and turbulent processes, advancing the fundamental understanding necessary for optimising fuel-air mixture formation and combustion efficiency in hydrogen DI engine development.

Dong, Shuo, Shi, Hao, Zhang, Gengxin, Feng, Yizhuo, Lu, Enshen, Wang, Xinyan, Zhao, Hua

Thermal Management in Electrified Transportation: A Comparative Study of Different Powertrain Technologies

2025-28-0412

10/30/2025

The transition towards sustainable transportation necessitates the development of advanced thermal management systems (TMS) for electric vehicles (EVs), hybrid electric vehicles (HEVs), hydrogen fuel cell vehicles (FCVs), and hydrogen internal combustion engine vehicles (HICEVs). Effective thermal control is crucial for passenger comfort and the performance, longevity, and safety of critical vehicle components. This paper presents a rigorous and comparative analysis of TMS strategies across these diverse powertrain technologies. It systematically examines the unique thermal challenges associated with each subsystem, including cabin HVAC, battery packs, fuel cell stacks, traction motors, and power electronics. For cabin HVAC, the paper explores methods for minimizing energy consumption while maintaining thermal comfort, considering factors such as ambient temperature, humidity, and occupant load. The critical importance of battery thermal management is emphasized, with a focus on preventing thermal runaway and maximizing battery lifespan through precise temperature regulation. The complexities of fuel cell stack thermal management are addressed, considering the electrochemical reactions and the need for uniform temperature distribution for optimal performance and durability. Furthermore, the paper investigates the thermal behavior of high-power traction motors and power electronics, analyzing different cooling techniques and their impact on efficiency and reliability. A comparative assessment of various cooling technologies, including forced air convection, liquid cooling, and emerging two-phase cooling methods, is provided. The paper also delves into integrating these individual TMS components, exploring opportunities for waste heat recovery and holistic system optimization. Finally, the paper identifies critical research gaps and outlines future directions in the development of intelligent and adaptive thermal management systems for next-generation electrified vehicles, emphasizing the need for robust control algorithms, advanced materials, and innovative cooling architectures.

K, Neelima, K, Anisha, Ch, Kavya, C, Somasundar, Satyam, Satyam, P, Geetha

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