Browse Topic: Fuel injection

Items (4,371)

Analysis of Full Torque Determination in a Diesel Engine Operating in Dual Fuel mode with Hydrogen and Diesel

2026-24-0014

9/21/2026

A 15kW diesel engine is modified in the laboratory to operate in dual fuel combustion mode. The engine is a three-cylinder, displacement of 1 Liter, originally fueled with diesel in its baseline configuration. The engine is modified by installing three PFI injectors, positioned toward the intake valves within the intake manifold. Hydrogen injection is synchronized with valve opening during the engine cycle using controlled delay units. The standard diesel injection system, managed by the original ECU, initiates combustion of the premixed air/hydrogen charge. The dual fuel operation is tested at 2000 rpm maximum torque. To maintain this condition, both diesel quantity through accelerator input and hydrogen flow via injectors duration are adjusted. Constraints included reducing diesel fuel and avoiding knock caused by excessive hydrogen. The engine operated reliably under all tested conditions. A maximum hydrogen energy substitution HES of 70% is achieved at high load, though higher values increased PPRR. A premixed equivalence ratio of 0.40 is identified as the limit before self-ignition occurred. To prevent this and achieve maximum power, an alternative strategy is introduced. Starting from diesel-only maximum torque, diesel is gradually reduced while hydrogen is increased. Rated torque is successfully achieved with an HES up to 45%. These results demonstrate that dual fuel operation can significantly reduce fossil fuel consumption while maintaining performance. It provided combustion stability and knock limits carefully managed through appropriate control of mixture composition. Further optimization could enhance efficiency and emissions performance in future applications.

Mancaruso, Ezio, Rossetti, Salvatore, Cameretti, Maria Cristina

Tailoring ICEs Towards Future Global Market Requirements – Multi-Fuel Capability To Ensure Next Decade Market Success

2026-24-0030

9/21/2026

The entire mobility industry currently faces enormous regulatory demands due to the Paris agreement and its corresponding initiatives to eliminate the business sector-related greenhouse gas emissions (GHG) emissions. A major focus is hereby set on wide-spread electrification of all kinds of applications, but from current perspective it is obvious that a quick and complete shift is highly unlikely, especially with view on heavy and challenging industrial and commercial applications. In line with this, it’s apparent that internal combustion engines (ICEs) maintain to play an important role in the overall propulsion system line-up. For compliance with the engaged CO2 reduction policies and efficiency improvement demands, a fast and broad replacement of fossil fuels needs to be realized. Due to the specific properties of carbon-neutral fuels and as well the variety of the range of industrial applications, different types of alternative fuels are considered. These novel fuels can be subdivided into preferred solutions for smaller or on-highway applications vs heavy off-highway and marine applications, or simply according to local or national preferences or policies. As of now, Hydrogen as well as Methanol/Ethanol is highly attractive for on-highway applications as well as construction/agricultural applications, the heavier and larger applications tend to more energy-dense energy carriers like NH3 and partially Methanol/Ethanol. In addition, to support a smooth transition to fully carbon-neutral operation, intermediate dual-fuel layouts are requested, partially requiring a full redundancy between classical Diesel operation and powering with new fuels. This complexity and variety in customer demands provide a major challenge for globally operating OEMs as future engines designs and definitions need to be developed under extreme cost pressure. The paper at hand delivers an interesting approach to design and develop modern ICE platforms for the anticipated multi-fuel case, aiming at superior key performance indicators concerning power output and efficiency, while maximizing the degree of commonality between the individual engine versions and variants. This flexibility and modularity needs to be incorporated in the base engine design, especially in the top end of the assembly, as it implicates different demands in air delivery and as well the transition from a diffusive combustion system to a pre-mixed combustion principle. This affects on one hand the installation of key sub-systems like fuel injection and ignition, but as well also the decision about an appropriate compression ratio and the definition of an adjusted in-cylinder charge motion. The article closes with recommendations for a future multi-fuel engine definition and an assessment concerning the major design changes in contrast to a refined and optimized Diesel engine layout.

Koerfer, Thomas, Dhongde, Avnish, Yadav, Jaykumar

Experimental and Numerical Investigation of Hydrogen Direct Injection in a CI Engine

2026-24-0004

9/21/2026

Compression ignition (CI) engines are widely used in the transportation sector due to their high torque and efficiency. However, the current climatic framework limits their application, favouring the adoption of low- and zero-carbon technologies. In this context, hydrogen represents a viable energy source for driving CI engines towards clean combustion. The benefits of hydrogen enrichment in diesel engines have been extensively investigated, particularly in port fuel injection (PFI) configurations. In contrast, the addition of a hydrogen direct injection system within a Common Rail engine remains largely unexplored. In this work, a piezo-actuated outward-opening direct injector fuelled by hydrogen was investigated through a combined experimental and numerical approach. The experimental campaign was conducted on an optically accessible single-cylinder research engine (SCRE), with the injector mounted in the cylinder head. Different injection strategies were explored in terms of duration, while the start of injection (SOI) was fixed at 2° after the inlet valve closure (IVC). In parallel, numerical simulations were performed to analyse the injection process into the engine. Firstly, a zero-dimensional model was developed to provide a preliminary estimation of the pressure within the system during the injection phase. Subsequently, computational fluid dynamics (CFD) simulations were performed to obtain a more detailed prediction of the injection process. The numerical framework reproduced the transient injection phase by modelling the near-nozzle jet development and its interaction with the in-cylinder charge. Based on the combined experimental and numerical results, the effective discharge coefficient of the injector is evaluated under different injection durations, enabling a quantitative assessment of its performance.

Episcopo, Domenico, Rossetti, Salvatore, Mancaruso, Ezio, Saponaro, Gianmarco, Lorusso, Leonardo, Camporeale, Sergio, Laera, Davide

Thermal Effects and Combustion Behavior of Hydrogen and Natural Gas in a Heavy-Duty Gas Engine

2026-24-0003

9/21/2026

To accelerate the adoption of renewable fuels in heavy-duty transportation, a conventional diesel engine was retrofitted to operate on gaseous fuels. This approach supports the transition from diesel to renewable energy carriers while maximizing the reuse of existing engine platforms. However, converting a liquid-fuel engine to gaseous operation does not inherently ensure stable or efficient performance. Gaseous fuels require external ignition, and hydrogen, with its low minimum ignition energy and wide flammability range, places particularly high demands on combustion development. In spark-ignited heavy-duty gas engines, port fuel injection (PFI) is widely used because of its simpler integration and lower fuel-pressure requirements compared with direct injection (DI). However, PFI reduces volumetric efficiency and increases sensitivity to abnormal combustion, including backfire and pre-ignition. DI can mitigate these limitations by enabling fuel delivery after intake valve closure and allowing later injection timings, thereby improving system efficiency and mixture formation control. Experiments were conducted on a 1991 cc single-cylinder research engine representative of heavy-duty applications. Two fuel supply systems were evaluated: low-pressure PFI up to 15 bar and high-pressure DI up to 200 bar. Two novel injector designs were tested with hydrogen and natural gas to assess the effects of fuel type, pressure level, load, and speed. The cylinder head was instrumented with ten thermocouples to evaluate local thermal distribution. In parallel, exhaust emissions, including NOx, hydrogen slip, and unburned hydrocarbons, were analyzed to link injection strategy, mixture formation, combustion behavior, emissions, and thermal loading.

Rößlhuemer, Raphael, Fitz, Patrick, Fellner, Felix, Prager, Maximilian, Jaensch, Malte

A Computational Study of High Efficiency Wankel Rotary Engines using a Passive Pre-Chamber

2026-24-0001

9/21/2026

Wankel rotary engines are renowned as compact machines with high power-to-weight ratios, which make them suitable for use as range extenders for battery electric vehicles or as propulsion systems for unmanned aerial vehicles. However, their overall efficiency and emissions still need significant improvement to meet to the stringent regulations comparable with classical reciprocating 4-stroke engines. With the aim of improving these shortcomings, this work focuses on the application of a passive pre-chamber in order to enhance the combustion phase and the overall efficiency and emissions of such engines. Computational fluid dynamics (CFD) simulations were conducted for the commercial AIE 225CS rotary engine, configured with port fuel injection and fully-premixed gasoline combustion. The engine was extensively tested in a previous project while different CFD models were validated against experimental data in previous studies by the same authors. In particular, the present work examines the engine performance with two pre-chamber configurations with different volumes. The volume and nozzle specifications were determined to have geometrical characteristics similar to those of the theory of Gussak, with volumes directly comparable with that of the two spark park plug recesses of the original engine, leading to significantly large nozzle diameters in the pre-chambers. In addition, the effect of spark advance was investigated to capture the development of the flame and jets and the resulting effects on the indicated pressure cycle. Consistent with previous findings, heat losses were found to be a critical aspect for the different configurations of engine. Nevertheless, the application of pre-chamber shows some potential to improve efficiency by accelerating combustion phase, leading to a relative increase of 7.4% on the indicated efficiency. This suggests an important new path in the development of Wankel engines as a viable solution to efficient utilisation of decarbonised and innovative future fuels in compact systems.

Vorraro, Giovanni, Im, Hong G., Turner, James

Business Approach to Cope with Automotive Market Uncertainty

2026-24-0024

9/21/2026

The global automotive industry is facing an unprecedented convergence of uncertainties driven by geopolitical tensions, evolving trade policies, emissions related regulations, and increasingly volatile consumer demand. Shifting emissions legislation, including the EU’s tightened CO2 targets and long-term plans to phase out internal combustion engines, is imposing strategic and financial pressures on automakers and suppliers as they navigate divergent regional regulatory trajectories. Demand side volatility further complicates the landscape. Consumer preferences are fluctuating due to economic pressures, infrastructure constraints, and uneven EV adoption patterns. While some markets show stagnation in battery electric vehicle uptake, hybrids are rising as consumers seek cost efficient alternatives amid uncertain energy and regulatory environments. Within this unstable context, the transition toward Software Defined Vehicles (SDVs) is emerging as a critical strategic response. SDVs, characterized by centralized computing, updatable software architectures, and over the air feature deployment, offer automakers greater adaptability in addressing regulatory shifts and market dynamics. By decoupling hardware from software cycles, SDVs enable faster innovation, reduced development risk, and new digital revenue models, while virtualization and AI driven analytics enhance development efficiency and lifecycle value.

Cavanna, Filippo, Potenza, Luca

A Simple and Efficient THINC Scheme for Multiphase Flow via Dominant-Material Selective Reconstruction

2026-99-1229

9/4/2026

Multiphase compressible flow problems are widespread in aviation, aerospace, transportation, military, and industrial fields, for instance, in underwater explosion bubble dynamics, fuel injection for hypersonic vehicles, liquid sloshing in propellant tanks, and supercavitating underwater vehicles. This paper proposes an improved THINC (Tangent of Hyperbola for Interface Capturing) method for multiphase flow simulations, based on a selective reconstruction strategy for the dominant material. The core of the strategy is to apply the THINC reconstruction exclusively to the material with the largest volume fraction within a multiphase mixed cell, which numerically governs the local interface evolution. The volume fractions of non-dominant materials are then obtained through a proportional distribution that inherently ensures the summation (Σαk = 1) and boundedness (0 ≤ αk> ≤ 1) constraints are met without explicit corrections. This approach reduces the number of THINC reconstructions for each time step in a multiphase mixed cell from Nm (the number of materials) to one, significantly simplifying the algorithm and lowering computational cost. It thereby avoids the error accumulation and complex renormalization procedures associated with conventional schemes that reconstruct all materials. While strictly maintaining volume fraction conservation, the proposed method preserves interface sharpness through the underlying THINC framework. The method is implemented in a diffuse-interface, multiphase Eulerian framework and validated with a series of challenging benchmarks, including shock-helium bubble interaction, triple-point problem, gas impact, and the more complex modified gas impact. Numerical results show that, compared with conventional multiphase THINC approaches that reconstruct every material, the proposed scheme can reduce CPU time by about 40.0% without compromising the accuracy of key physical quantities.

Wang, Wei, Zhong, Yanxu, Hu, Qinghua, Yang, Canqun

Study of Port Fuel Injection Engine Cold Start Unburned Hydrocarbons Reduction Using Computational Fluid Dynamics with a Reduced Iso-Octane Mechanism Considering Various Isomers and Thermal Decompositions

03-19-04-0021

8/27/2026

A modeling study was performed to find solutions to reduce the unburned hydrocarbons during cold start of a PFI (port fuel injection) SI (spark ignition) engine. Through modeling, the root cause for the high unburned hydrocarbons of the baseline engine during cold start was found. The slow combustion, which is due to the high amount of exhaust gas flowing back into the intake port and then becoming trapped inside the cylinder, is the root cause. A new valve lift, which can reduce the internal residual by 26%, was designed. Along with a fuel amount decrease of 35%, the UHC (unburned hydrocarbons) before the three-way catalyst can be reduced by 40%. The exhaust temperature using the new valve lift design increases by 400°C, which improves the performance of the three-way catalyst for further reducing UHC. In addition to the adoption of the new valve lift, an active SAI (secondary air injection) strategy was also investigated. Modeling results show that SAI can promote secondary combustion in the exhaust pipes to increase exhaust temperature and thus is beneficial for further oxidizing unburned hydrocarbons. The amount of active SAI mass flow rate should be controlled to less than 25% of the intake air flow rate to avoid the cooling effect dominating over the oxidation process. The duration of SAI should be from EVO (exhaust valve opening) to IVO (intake valve opening). For combustion modeling, a newly reduced iso-octane chemical kinetic mechanism was developed using carbon flux analysis to extract major reaction pathways for a wide range of practical engine temperature conditions. In the new reduced mechanism, a skeletal sub-mechanism for species starting from iso-octane to C4 is coupled with a recently updated H2/O2/CO/C1–C4 detailed sub-mechanism. Including a reduced NOx (oxides of nitrogen) sub-mechanism, the final mechanism has 681 species and 3332 reactions. Before the new reduced iso-octane mechanism was used, it had been validated with available experimental data of ignition delay times, laminar flame speeds, and important species profiles in the literature. Both the investigation of PFI engine unburned hydrocarbons reduction under cold start operating conditions and the development of a reduced chemical mechanism are the objectives of this work.

Guo, Dongshao, Zhang, Licheng, Yang, Shiyou, Bourg, Cyrus, Sun, Yong, Abidin, Zainal, Lin, Shujun

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

Experimental Investigation on Unburned Methanol and Formaldehyde Emissions from a Direct-Injection Diesel / Methanol Dual-Fuel Engine

2026-99-1646

7/24/2026

For large-bore marine methanol / diesel dual-fuel engines, this study investigates the formation characteristics of unregulated emissions through experimental methods and explores the mechanisms by which engine load and injection timing influence the emissions of unburned methanol and formaldehyde. The study was carried out on a supercharged intercooled inline six-cylinder engine, and Fourier Transform Infrared Spectroscopy (FTIR) was used to monitor the exhaust composition in real time. The study shows that methanol released in the exhaust is due to the incomplete combustion of the methanol fuel. In the combustion process of methanol fuel, formaldehyde mainly arises from two pathways, the first of which is the partial oxidation of methanol inside the cylinder; secondly, the unburned methanol in the exhaust gas oxidizes in the exhaust pipe to generate formaldehyde. As the load increased from 25% to 100%, the unburned methanol emissions decreased by 29%, and formaldehyde emissions decreased by 71%. This is mainly attributed to the enhanced oxidation reaction and reduced wall crevice effect due to the increased combustion temperature. Methanol injection timing optimization was effective in controlling unregulated emissions, with methanol emissions lower at -7° CA ATDC and formaldehyde emissions reaching larger values under this condition. Delaying the diesel injection to -16°CA ATDC led to a 38% increase in unburned methanol emissions, caused by fuel spray interactions and longer stagnation, whereas formaldehyde emissions showed minimal change.

Jiang, Yuqi, Li, Hongmei, Zhang, Wenzheng, Li, Xiao, Zheng, Liang, Meng, Yangqian, Gu, Xianan, Hua, Hanqing

Drop Impact Phenomena: An Experimental Study of Isooctane Interaction with Dry Walls and Liquid Films

2026-01-5015

7/13/2026

In this study, high-speed back-illuminated imaging and laser-induced fluorescence (LIF) methods were employed to investigate the impingement behavior of millimeter-sized single isooctane drops on a dry solid wall and various liquid films, including isooctane and glycerol solution films of different concentrations. Various fuel spray impingement scenarios in gasoline direct injection engines were examined. High-speed back-illuminated imaging was primarily used to examine the impact of fuel drops on a dry wall and a fuel film of the same composition as the drops. The LIF method was used to examine the impact of fuel drops on the glycerol solution film, allowing for the distinction between fuel drops and the glycerol solution film. The impingement behavior varied depending on the Weber number of the incident drop and the wall condition. When fuel drops impacted the solid dry wall vertically, they spread into a circular liquid film. The outer edge of the liquid film folded and bulged, and upon reaching the maximum spreading diameter, it maintained equilibrium and did not retract. When isooctane fuel drops impacted the isooctane film, they broke and splashed, with thinner films producing stronger splashes. Additionally, the Weber number of the fuel drops significantly influenced the crown shape and splashing after impact. The impingement behavior of fuel drops on the glycerol solution film was also investigated, focusing on the liquid film morphology after impact. Based on the experimental data, empirical correlations were established between the critical Weber numbers for transitions among different crown morphologies and the dimensionless film thickness under varying film viscosities.

Yang, Tian, Lu, Lili, Guo, Zongwei, Song, Enzhe, Yao, Chong, Ning, Yilin, Ke, Yun

Study on Diesel-Methanol Non-Premixed Combustion Characteristics of a Marine Dual-Fuel Engine at Different Methanol Substitution Rate

2026-99-0517

7/10/2026

Methanol use in marine engines has the potential to reduce nitrogen oxide emissions, particulates, and greenhouse gas emissions. A turbocharged four-stroke marine diesel powerplant was converted to run as a double-DI (direct injection) diesel-methanol hybrid engine. Experimental studies using a non-premixed combustion scheme showed that higher methanol substitution ratios (MSR) led to increased peak heat release rates. The combustion process displayed distinctive two-phase behaviors. Increasing MSR caused retarded ignition timing, shortened combustion duration, and improved thermal efficiency. Combustion stability was significantly improved at higher MSR. Emissions results showed NOX and HC were increased in proportion to MSR, whilst particulate emissions and CO concentrations were inversely reduced. Methanol enrichment was found to enhance NOX and HC formation processes but also accelerate soot particulate decomposition and CO oxidation mechanisms.

Li, Xiao, Jiang, Yuqi, Yan, Ping, Zheng, Liang, Li, Hongmei, Zhang, Wenzheng, Chen, Chao, Man, Zhongguo

NO _x Formation Characteristics of Lean Hydrogen Combustion: From 0D Analysis to Comprehensive 3D-CFD Engine Investigations

2026-01-0732

7/1/2026

The transition toward climate-neutral transportation requires powertrain concepts that combine high efficiency with low pollutant emissions. In this context, hydrogen-fueled internal combustion engines represent a promising solution when hydrogen is produced from renewable energy sources. Owing to its specific molecular properties, hydrogen offers new possibilities for influencing and optimizing the combustion process and reducing the emission formation. This paper presents a numerical approach for characterizing the NOx formation in a single-cylinder research engine equipped with port fuel injection and a passive pre-chamber ignition system. The single-cylinder is operated over a wide range of engine loads and speeds, covering air-to-fuel ratios from λ=1.5 to 2.5 and achieving up to 23 bar indicated mean effective pressure. The study focuses on the influence of engine load and mixture composition on NOx emissions. A dedicated look-up table approach in combination with several reaction parameters based on the extended Zeldovich mechanism are evaluated through comparison with experimental data. Furthermore, multiple sampling positions within the CFD mesh are examined. The simulations reproduce measured trends across variations in load and air-to-fuel ratio with good accuracy. At high load and λ=1.5, NOx emissions of up to 6000 ppm are produced, decreasing exponentially with increasing excess air. Finally, potential NOx reduction strategies for the single-cylinder are examined. While influencing the mixture homogenization shows limited effectiveness, temperature-based actions prove to be more effective. Among the investigated approaches, a Miller intake valve strategy yields the largest benefit, achieving approximately 10% NOx reduction by lowering end-of-compression temperatures and increasing residual gas dilution under otherwise identical operating conditions.

Gal, Thomas, Vacca, Antonino, Chiodi, Marco, Schmelcher, Robin, Kulzer, Andre Casal

Experimental Study of Warm-Up And Startability Operations in a Spark Ignition Engine Fueled with Ethanol Gasoline Blends

2026-01-0738

7/1/2026

The mitigation of Greenhouse Gas (GHG) emissions poses a major challenge for the transportation sector, driving the need for renewable fuels. Bioethanol represents a promising fuel for Spark-Ignition (SI) engines, combining a reduced life-cycle CO₂ impact with advantageous combustion properties. However, despite its proven performance under steady-state conditions, the widespread of fuels with high ethanol content is still constrained by significant difficulties during engine cold-start operation. This study aims to experimentally assess the effect of ethanol concentration on cold-start performance and warm-up transient behavior of a Naturally Aspirated (NA), Port Fuel Injected (PFI) SI engine. Warm-up tests were conducted at an operating condition of 2000 rpm engine speed and 20 Nm torque using three fuels with increasing ethanol content: commercial gasoline (E5), E30 and E60. In addition, dedicated startability tests were carried out for E60 and neat ethanol (E100) at different initial engine wall temperatures to evaluate fuel sensitivity to thermal conditions during engine start. The experimental results indicate that increasing ethanol concentration has a negligible effect on the overall duration of the warm-up process, while leading to a modest reduction in both engine wall and exhaust gas temperatures. At the same time, E100 displays severe startability limitations at low initial wall temperatures, requiring repeated cranking attempts before stable operation can be achieved. The same startability issues have been observed for E60 but with limited intensity. Two minimum engine wall temperature ranges were identified for reliable cold-start operation at 20-25 °C for E60 and 25-30°C for E100. Overall, these findings experimentally confirm the dominant influence of engine thermal conditions on the reliable startability of ethanol-fueled spark-ignition engines.

Falbo, Luigi, Falbo, Biagio, Perrone, Diego, Castiglione, Teresa

Spray–Wall Interaction at Thermal Swing Coatings in SI Engines

03-19-03-0014

6/25/2026

As a contribution to the reduction of greenhouse gas emissions in the transportation sector, the indicated efficiency of SI engines can be increased via thermal swing coatings. Thereby, a decrease in greenhouse gas emissions can be achieved, although not at all operating conditions. Here, the often-observed increased hydrocarbon emission partially overcompensates the reduced wall heat losses. The main root cause is always attributed to the increased surface roughness and porosity, leading to an increased crevice volume. Further investigations were performed at a single-cylinder engine equipped with a FTIR for species analysis of hydrocarbon emissions. A comparison of direct injection and port fuel injection were performed for RON95 E10 and methanol to assess the influence of mixture preparation. 3D CFD was used to additionally investigate the in-cylinder processes. The comparison of port fuel injection and direct injection showed a significant influence on the fuel hydrocarbon emissions for the direct injection when the thermal swing coating was applied. The effect is more pronounced for methanol. For port fuel injection nearly the same or reduced fuel hydrocarbon emissions can be observed. This is mainly attributed to an increased wall film agglomeration at the piston for the thermal swing coating in case of direct injection, which can be observed in 3D CFD. Due to the low thermal effusivity of the coating, the droplet impingement leads to a notable decrease in the surface temperature. This results in lower evaporation of the fuel and a longer droplet lifetime. Consequently, a fuel wall film is still present at top dead center after ignition leading to additional hydrocarbon emissions.

Fischer, Marcus, Pischinger, Stefan

CFD Modelling of an Asymmetric Hydrogen Injector Cap for Direct Injection Applications: Design Impact on Jets Structure and Momentum Flux

2026-37-0011

6/9/2026

The adoption of hydrogen as a carbon-neutral sustainable fuel for internal combustion is regarded as a promising solution to reduce greenhouse gases and pollutant emissions. In this framework, the injection system plays a crucial role, being responsible for delivering a large amount of fuel to the combustion chamber. Currently, low-pressure direct injection is considered one of the best solutions to ensure the appropriate fuel delivery. The use of caps has proven particularly effective, as they enable a potentially unlimited range of geometries while minimizing modifications to the injector hardware. Experimental campaigns and computational fluid dynamics (CFD) simulations can be used together as complementary tools to speed up the development process and explore multiple combinations of parameters, thereby optimizing the overall design of both the engine and the caps. In the present paper, a single-hole GDI-derived hydrogen prototype injector equipped with a two-hole asymmetric cap and fed with hydrogen is analyzed through both experiments and CFD simulations under two different operating conditions in terms of rail pressure. Cap pressure, overall fuel instantaneous mass flow rate and hole-specific jet momentum have been measured during the experimental campaign. The resulting data were used as boundary conditions and as targets for the validation of steady-state CFD computations, where the same equipment has been simulated. In particular, the momentum flux produced by the two jets emerging from the forming cap was used to validate the numerical methodology against experimental outcomes. Moreover, the exact dimensions of cap holes have been taken by means of optical microscope and applied to the simulation to compare the real geometry against the nominal one. Therefore, the impact of the effective cap geometry is explored, evidencing a noticeable dependence specifically of the cap backpressure and therefore of the injection system performance on the details of the cap design.

Pavan, Nicolo, Breda, Sebastiano, Duni, Andrea, Martino, Manuel, Fontanesi, Stefano, Postrioti, Lucio

Comparison of Detailed Chemistry and Flamelet-Based Models for Hydrogen Combustion in a Heavy-Duty PFI Engine

2026-37-0014

6/9/2026

Addressing climate change requires substantial reductions in CO2 emissions from the transportation sector, where alternative fuels for internal combustion engines play a crucial role. Hydrogen stands out as a compelling energy carrier capable of enabling low-carbon combustion while leveraging existing engine technologies. Its adoption can support a transition toward fuel-flexible powertrains and deliver rapid decreases in exhaust carbon emissions. This approach is particularly relevant for hard-to-abate segments, where full electrification remains challenging. Building on this perspective, this numerical study investigates the modelling behaviour of a heavy-duty port fuel injection (PFI) internal combustion engine fuelled with hydrogen. Initially, the mixture was assumed to be fully premixed to avoid uncertainties related to injection and mixing processes and to significantly reduce computational cost; this assumption was subsequently validated through selected injection simulations. A methodology was then developed to ensure robust model responses by analysing convergence over three consecutive cycles and by appropriately defining the initial and boundary conditions, as well as mesh resolution. Three representative experimental operating points were investigated: full load, maximum power, and cruise conditions. Two combustion modelling approaches were then compared. ECFM, a flamelet-based model, demonstrated its ability to match experimental data through a calibration process that accounts for turbulence-chemistry interactions via the adjustment of model parameters. In contrast, SAGE is a detailed chemistry solver that employs a kinetic reaction mechanism to directly compute reaction rates, without requiring calibration. The comparison highlighted certain limitations of SAGE arising from its underlying approach, whereas ECFM showed more stable and reliable behaviour, albeit with the need for case-specific calibration.

Scopelliti, Alex, Misul, Daniela Anna, Baratta, Mirko, Gallo, Alessandro, Rapetto, Nicola, Vargiu, Luca

Experimental Investigation on Cold Start and Warm-Up Phases for an Ethanol Fueled SI Engine

2026-37-0031

6/9/2026

The reduction of Greenhouse Gas (GHG) emissions represents a key challenge for the transportation sector, requiring the adoption of renewable fuels capable of ensuring both environmental benefits and compatibility with existing internal combustion engine technologies. In this context, bioethanol emerges as a viable solution for Spark Ignition (SI) engines, offering a low life-cycle CO₂ footprint and favorable combustion characteristics. Nevertheless, despite its well-known advantages under steady-state operation, the widespread use of high-ethanol-content fuels is still limited by critical issues during engine cold start. The aim of this work is to experimentally investigate the influence of ethanol content on cold-start behavior and idle warm-up transient operation of a Naturally Aspirated (NA), Port Fuel Injected (PFI) SI engine. The experimental campaign was carried out under idle conditions using four fuels with increasing ethanol content, namely commercial gasoline (E5), E30, E60, and neat ethanol (E100). Cold-start and full warm-up tests were performed starting from ambient temperature, while additional dedicated experiments were conducted on E100 to evaluate startability under different initial engine wall temperatures. The results show that increasing ethanol content has a limited impact on the overall warm-up duration, while slightly reducing engine wall and exhaust gas temperatures. Conversely, E100 exhibits pronounced startability issues at low initial wall temperatures, requiring multiple cranking attempts to achieve stable idle operation. A minimum wall temperature threshold in the range of 25-30 °C was identified as necessary to ensure reliable cold start with E100. The outcomes of this study provide experimental evidence of the key role played by engine thermal conditions in enabling stable operation of ethanol fueled SI engines during cold start.

Falbo, Luigi, Falbo, Biagio, Perrone, Diego, Castiglione, Teresa

Investigating the Potential of Two Individually Controlled Injectors per Rotor for a Direct Injection Hydrogen Wankel Engine

2026-37-0008

6/9/2026

Hydrogen-fueled rotary engines offer a promising zero-emission solution for compact commercial powertrains. This study reports experimental results from the further development of a naturally aspirated, direct-injection hydrogen rotary engine by HTM. Initial applications, such as an airport baggage tractor, demonstrated technical feasibility but revealed pre-ignition that limited maximum torque. To address this, mixture formation was investigated using an experimental setup with two independently controlled injectors feeding a single rotor injection channel. The effects on operating behavior, efficiency, and NOx emissions were evaluated. The dual-injector configuration significantly shortens injection duration and improves spatial distribution of hydrogen within the combustion chamber. Enhanced mixture control suppresses pre-ignition and enables higher mean effective pressure. Systematic variation of injection timing under representative steady-state conditions also shows potential for NOx reduction through differentiated injector operation. In-cylinder pressure analysis and exhaust gas measurements provide detailed insight into combustion characteristics and abnormal events. The dual-injector setup increases torque capability and operational robustness without additional mechanical complexity, supporting the use of hydrogen rotary engines in compact hybrid systems and stationary power applications.

Endres, Jonas, Beidl, Christian, Herold, Tim, Lavall, Philipp, Schmidt, Marvin, Hofmann, Silas, Kahl, Jonas

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

Effects of Engine Geometries on the Combustion Characteristics of a Heavy-Duty Hydrogen Spark-Ignition Engine

2026-37-0046

6/9/2026

For heavy-duty applications, hydrogen (H2) internal combustion engines offer a practical solution for future transportation. However, the influence of cylinder head flow characteristics and piston geometry on lean H2 combustion remains insufficiently understood. This study presents a comprehensive computational investigation of three engine configurations characterized by distinct in-cylinder flow dynamics: mild swirl and tumble (Engine a), strong tumble (Engine b), and strong swirl (Engine c). High-fidelity three-dimensional computational fluid dynamics simulations were performed for both port-fuel injection (PFI) and direct injection (DI) strategies. The impact of piston geometry was evaluated by comparing the baseline piston with a flat piston, while the spark timing was optimized to achieve favorable combustion phasing. Combustion and NOx formation were modeled using a G-equation-based combustion framework incorporating diffusive-thermal instability effects and a validated in-house H2 chemical mechanism. Turbulence-flame interactions were further characterized using Borghi-Peters diagrams. Under PFI operation, the strong-tumble configuration (Engine b) generated the highest turbulent kinetic energy (TKE), resulting in faster flame propagation, more advanced combustion phasing, and improved thermal efficiency. The flat piston further enhanced efficiency by reducing mixture confinement within piston-induced recirculation zones. Under DI operation, H2 injection significantly increased turbulence intensity, and a flat piston promoted higher TKE near spark timing in Engines b and c by reducing mixture-wall interaction, leading to faster combustion compared with the baseline piston. In contrast, the original piston produced higher TKE within the piston bowl in Engine a due to stronger recirculation. Additionally, the strong-tumble configuration achieved the most homogeneous mixture distribution under DI conditions. These results demonstrate that in-cylinder flow structure, piston geometry, and DI injection strongly affect turbulence generation, mixture formation, and combustion performance. The strong-tumble configuration shows the greatest potential for achieving high thermal efficiency with controlled emissions in lean H2 spark ignition engines.

Liu, Xinlei, Menaca, Rafael, Cenker, Emre, Silva, Mickael, Qahtani, Yasser A., Pei, Yuanjiang, Turner, James W.G., Im, Hong G.

Challenges of Mixture Formation in Methanol Port Fuel Injection Engines

2026-01-0337

4/7/2026

Port fuel injection (PFI) is an attractive strategy for methanol adoption in both spark-ignition and dual-fuel compression-ignition engines due to its lower cost and simpler hardware compared to direct-injection. However, methanol PFI mixture formation can be challenging due to methanol’s high heat of vaporization, low volatility at cold conditions and high tendency to wall wetting. Understanding and addressing these challenges is critical to ensure robust engine operation. In this study, the effects of injector geometry, coolant temperature, intake temperature and fueling rate on mixture formation of methanol PFI have been investigated for anhydrous methanol and for a blend of 90%vol methanol plus 10%vol water in an optical engine. Mie scattering and infrared imaging were applied to assess the liquid and vapor methanol distribution in the cylinder. For a high-flow injector compatible with methanol, significant amounts of liquid were detected in the cylinder at all conditions tested, leading to poor mixing and high fuel stratification during the compression stroke. This effect was mitigated by using a multi-hole injector that promoted better atomization, indicating that high atomization is preferred over high flow for methanol PFI. The probability of detecting liquid in the cylinder decreased as the coolant temperature or the intake temperature increased or if the fueling rate decreased, with coolant temperature being the dominant parameter to control methanol vaporization. Liquid probability increased with water addition mainly because of the high heat capacity of water. Liquid methanol accumulated in the intake port, decreasing the effective engine intake temperature and limiting fuel vaporization. This accumulation led to a delay of the system response to changes in the PFI settings, with injected fuel requiring one cycle to reach the cylinder and additional 50 cycles required to completely flush the fuel accumulated in the port. Finally, the operating envelope for liquid-free operation was defined.

Lee, Sanguk, Narayanan, Abhinandhan

Experimental Characterisation of Combustion, Performance, and Emissions in a Hydrogen Fueled Opposed Piston Engine

2026-01-0335

4/7/2026

Recent studies have demonstrated that the current Internal Combustion Engine (ICE) can be adapted to operate with hydrogen for the decarbonisation of transport and gensets. This is mostly done by conversion of conventional 4-stroke compression ignition diesel engines or spark ignition gas engines for heavy-duty vehicles or 4-stroke spark ignition gasoline engines for light-duty applications. This study aims to assess the adoption of pure hydrogen direct injection technology on a novel two-stroke opposed-piston engine designed by Carnot Engine Ltd. The engine provides a flexible platform that can operate in both compression ignition and spark ignition modes, allowing it to adopt multiple fuels. For the first time, a single cylinder prototype version of this new engine was operated and tested with hydrogen at Brunel University of London. During the engine experiment, a spark ignition timing sweep was carried out at low and mid-loads up to 10 bar IMEP to identify the Minimum ignition advance for Best Torque (MBT). Then, a complete mapping of the fuel injection strategies and lambda matrix was performed to optimise engine efficiency and combustion stability at low loads. The outcome of this study demonstrates an impressive indicated thermal efficiency of 58.7% at a load of 5 bar indicated mean effective pressure (IMEP) when the engine was operated with an ultra-lean mixture of lambda 3.2. Additionally, the engine-out NOx emissions decreased from the maximum 1863 ppm at lambda 1.38 to less than 20 ppm at lambda 3.2. Furthermore, the steady-state engine-out emissions show near-zero carbon emissions at all operating conditions.

Mohamed, Mohamed, Roeinfard, Nima, Wang, Xinyan, Zhao, Hua, Watts-Farmer, Archie, Rahman, Nadiur, Lempp, Francis

Numerical Study of Gasoline Direct Injection Sprays at Conditions Relevant to Engine Cold-Start Operation

2026-01-0338

4/7/2026

Gasoline direct injection (GDI) remains a key technology for enhancing engine efficiency and meeting regulated engine-out soot limits, particularly when combined with downsizing and boosted operation. The performance of modern GDI engines strongly depends on the in-cylinder spray process, which governs mixture formation and combustion quality under a wide range of operating conditions. In this context, computational fluid dynamics (CFD) is an effective tool for supporting the design and operation of an engine. However, accurately modeling a spray’s evolution —from early to late injections and across varying ambient conditions —remains a major challenge. This study employs a CFD framework with an optimized spray modeling approach to investigate spray morphology and dynamics under various engine cold conditions. Although all simulations are conducted with a single-injection setup, the early- and late-injection cases are designed to emulate different phases of split-injection operation by adjusting the injection duration as well as the ambient pressure and temperature conditions. The analysis spans injection pressures from 100 to 300 bar, incorporating detailed comparisons of two-dimensional projected liquid volume distributions and liquid volume fraction footprint at 15 mm downstream. The results reveal that under late-injection conditions, high pressure suppresses spray penetration, high temperature accelerates evaporation, and increased injection pressure enhances atomization and evaporation. Deviations between the nominal drill angle and the actual plume direction are identified, consistent with the narrower plume orientations observed experimentally. Overall, this work demonstrates the effectiveness of the current CFD framework, with optimized spray modeling, in capturing realistic spray momentum evolution across various engine-relevant operating conditions.

Lien, Hao-Pin (Paul), Torelli, Roberto, Zhao, Le, Park, Ji-Woong, Zhang, Anqi, Pei, Yuanjiang, Hwang, Joonsik, Lee, Kyungwon

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

Development of an ‘Online’ Combustion System Calibration Method using a Non-Dominated Sorting Genetic Algorithm

2026-01-0285

4/7/2026

Calibration is a major resource bottleneck and source of risk in powertrain technology development. A promising alternative to the typical design-of-experiments (DoE) approach is the use of a ‘Non-Dominated Sorting Genetic Algorithm’ (NSGA) calibration method, where an iterative process is used to directly identify the Pareto Fronts between performance metrics, for example, net mean effective pressure (NMEP) and NOx emission. The goal of the present work was to develop and demonstrate a fully ‘online’ combustion system calibration method based on an NSGA, where the algorithm operates directly on experimental data rather than empirical models as is typical in the literature. This was completed by first designing an optimal NSGA for combustion system calibration and then demonstrating its use for an experimental combustion system calibration on a single cylinder gasoline engine at one operating condition. Results from the design process here indicate that ‘online’ NSGAs have a strong potential to outperform traditional DoEs in the development of Pareto-optimal engine calibrations; however, NSGA performance is highly sensitive to the specific parameters used in the algorithm logic. The highest sensitivity was to the mutation logic within the genetic reproduction process, and second was the number of genes (calibrations) included in the overall process. Inclusion of both the Primary and Secondary non-dominated Pareto fronts in the set of Pareto-optimal calibrations was found to be critical to the success of the NSGA. When demonstrated for an experimental combustion system calibration the NSGA operated effectively and as expected, continually providing ‘upward’ pressure to generate calibrations that maximize NMEP but also ensure the breadth of the Pareto front (NOx) is scanned with high fidelity. In comparison to a traditional DoE approach, the NSGA was nearly twice as accurate in identifying calibrations along the Pareto front for the same number of total experiments. The Pareto-optimal calibrations developed by the NSGA are reasonable for these operating conditions and in excellent agreement with the literature. The present work strongly motivates and supports further development of NSGA methods for use in more complex systems and situations including for electrified and hybrid powertrains.

Mansfield, Andrew

Study of Deposit Control Additive Efficacy in Gasoline Direct Injection Engines

2026-01-0349

4/7/2026

There is an increasing adoption of Direct-Injection Spark-Ignition (DISI) engines in the market, which per 2024 US Environmental Protection Agency (EPA) Automotive Trends Report represents 73% of new vehicles sold in the US. And while it is well accepted that DISI offers advantages over Port Fuel Injection (PFI) technology in meeting stringent CO2 emissions and fuel economy requirements set by the EPA, DISI engines are also associated with increased formation of injector deposits. These deposits may foul injectors and accumulate on the injector tip causing distorted spray patterns and diffusive combustion. Ultimately, this leads to engine performance deterioration and increased harmful emissions. To control deposit formation, detergent-type chemistries are added to the fuel in small amounts. Deposit Control Additives (DCAs) function by preventing the formation of deleterious injector deposits as well as removing existing ones. This study used standardized protocols describing the assessment of DCA in controlling injector deposits that have been developed by industry in both the US and Europe. When used at standard concentrations, DCA showed some engine performance and emission benefits over untreated base fuel. This investigation also demonstrated that engine performance can be recovered, in an engine with fouled injectors, with the use of higher DCA concentrations, accompanied by improved fuel economy and reduced particulate and total hydrocarbon emissions. This further confirms previous findings that, although DCA increases gum levels in the fuel, higher concentrations of DCAs improve injector cleanliness enough to outweigh any negative impacts from the increased gum content.

Soriano, Nestor, Williams, Rod, Cracknell, Roger, Lang, Wendy, Chahal, Jasprit

The Influence of Split Injection Ratio on Efficiency and NO _x Emissions in a Pilot Diesel-Ignited Hydrogen Direct Injection Engine

2026-01-0329

4/7/2026

This study investigates the impact of the hydrogen split injection ratio on the combustion of pilot diesel-ignited hydrogen direct-injection engines, which is expected to affect hydrogen-air mixture conditions and thus flame propagation and diffusion flame developments. Experiments were conducted on a 1-litre single-cylinder diesel engine equipped with an additional hydrogen injector operating at 35 MPa. Hydrogen accounting for 95% of total input energy was injected at 150 and 60 °CA bTDC for the first and second pulses, which were selected as high-efficiency injection timings from previous equal-split injection tests. The 5% diesel energy was injected near TDC to control CA50 at 10 °CA aTDC. While varying the split ratio between the two hydrogen injections, in-cylinder pressure/aHRR profiles, engine efficiency/power output and engine-out emissions of NOx and CO2 were evaluated. Results showed that the hydrogen split ratio does not significantly affect IMEP/efficiency, which consistently achieved a 17.2% increase over the diesel baseline. While CO2 emissions remained at a very low level due to high substitution of hydrogen energy, they showed no dependency on the split ratio. By contrast, NOx emissions were highly sensitive to the hydrogen injection split ratio. Increasing the first hydrogen injection fraction to 30% reduced NOx, attributed to decreased locally rich mixtures formed by late second hydrogen injection and increased lean mixture homogeneity from early first hydrogen injection, leading to a slower burning effect. However, further increasing the first injection fraction led to higher NOₓ emissions due to increased hydrogen compression, which raised TDC and combustion pressure.

Zhao, Yifan, Chan, Qing Nian, Kook, Sanghoon

Achieving Euro 7 WHSC NOx Emission Targets from a Spark Ignited Engine Using Methanol-Hydrogen Co-Fuelling

2026-01-0321

4/7/2026

E-methanol is increasingly seen as a promising clean fuel because its chemical makeup is close to fossil fuels, making it easier to use in existing engines. It offers a carbon-neutral option to help reduce greenhouse gases in sectors where cutting emissions is especially difficult, such as transportation. However, while e-methanol avoids adding new carbon dioxide, burning it in internal combustion engines still releases harmful gases like oxides of nitrogen (NOx) and other toxic by-products like formaldehyde and formic acid that damage both health and the environment. This report explores a new strategy that combines methanol with hydrogen to run engines under “ultra-lean” conditions and its impact on emissions, performance and efficiency. Experiments were carried out on a single-cylinder spark ignition engine, with directly injected methanol and port fuelled injection of hydrogen. The findings show that adding about 10% hydrogen (energy basis) at low engine loads can extend the lean limit from air-fuel equivalence ratio (λ) of 1.7 to 2. This change cut NOx emissions by 99% and reduced formaldehyde emissions by 18% compared to pure methanol operation at stoichiometric. Furthermore, the NOx emissions were reduced sufficiently that engine could operate within Euro 7 World Harmonic Stationary Cycle (WHSC) limits.

Ambalakatte, Ajith, Geng, Sikai, Cairns, Alasdair, Varaei, Amirata, Harrington, Anthony, Hall, Jonathan, Bassett, Mike, Cracknell, Roger

Optimal Strategies for SI H2 Combustion System and Pre-Ignition Investigation through Advanced Optical Techniques

2026-01-0324

4/7/2026

The rapidly transforming mobility sector is confronted with a dual challenge: achieving market expansion while significantly reducing emissions. Even if vehicle electrification tends to be favored in developed nations, it is widely acknowledged that no single solution is universally optimal. Within this context, hydrogen emerges as a compelling energy vector. It can be used both in fuel cells and internal combustion engines. This latter benefits from a well-known architecture and existing production infrastructures constituting a viable short-term and cost-effective solution especially for light or heavy-duty and off-road applications. In this context, investigation on the hydrogen spark-ignited internal combustion engine was performed, focusing especially on critical abnormal combustions. Indeed, during early development phase, abnormal combustion management was a challenge requiring the identification of the root cause of these issues. This work, based on the use of a versatile single-cylinder engine, is dedicated to the optimization of hydrogen combustion through adaptations of injection strategy to minimize the NOx production and improve the combustion efficiency. A dedicated attention was paid to study the effects of different parameters of the hydrogen injection system, such as the location of the injector, the targeting and the injection pressure. Subsequently, a specific cylinder head has been designed to allow endoscopic optical access into the combustion chamber for a visualization of the combustion related phenomena using a high-speed UV intensified camera. The work was especially focused on abnormal combustion analysis such as pre-ignition and allows to analyze the behavior of different spark plugs. Different injection configurations were tested and their effects on combustion were evaluated using both adiabatic heat release rate analysis and in-cylinder movies obtained through the optical setup described above. It provides valuable data about mixture preparation, flame propagation and cycle to cycle fluctuations. Conventional heat release rate analysis gives macro level data of the combustion stroke whereas the endoscopic images provide 2D flame fields that enhance the understanding of the combustion characteristics. This work finally leads to a better understanding of abnormal combustion occurrences and guides towards the choice of relevant injection and ignition strategies, especially at full load.

Londos, Benoit, Bardi, Michele, Serrano, David, Laget, Olivier, Gautrot, Xavier, Bramoullé, Clément, Cordier, Matthieu

A Novel Chemical Clustering Approach for the Acceleration of 3D CFD Simulations of Internal Combustion Engines with Complex Fuels

2026-01-0495

4/7/2026

Detailed kinetics simulations coupled with 3D CFD offer a powerful analysis tool for combustion and emissions. Such methods allow consistent modeling of multi-component fuels from evaporation to combustion and correctly capture the effects of local inhomogeneities created by preferential evaporation on the performance and emissions of modern powertrains. Such computations are extremely computationally demanding, prompting interest in the development of calculation acceleration techniques that can effectively balance the speed and accuracy of the chemical source calculation terms. Chemical kinetics clustering methods are widely used for that effect. However, such techniques must be not only effective but also robust with respect to the engine conditions and fuel composition changes, to reduce the computational demands introduced by the need to calibrate the parameters of the acceleration method itself. In this paper, an extended chemical kinetics clustering approach is proposed. A calibration methodology for the parameters of this acceleration method is then introduced, based on multi-point single time step optimization for a toluene reference fuel (TRF) surrogate with ESTECO modeFRONTIER, utilizing frozen 3D CFD fields obtained with the Realis Simulation VECTIS code. The optimal clustering parameters thus constructed are then fine-tuned through a DoE exercise performed in VECTIS for the combustion event with the TRF surrogate using a coarse computational mesh. The robustness of the optimal parameters is then evaluated through the application of different perturbations to the species fields. Finally, the optimal clustering parameters are applied to full-load simulations of a typical GDI engine with simple TRF and 8-species E10 gasoline surrogates. The results demonstrate that the acceleration parameters determined by this workflow deliver 2.4× to 4.2× acceleration of combustion source calculation and 1.3× to 1.8× acceleration of the overall simulation while preserving solution accuracy and keeping the resolution of NO and soot emissions within 10% and 15%, respectively. The proposed methodology facilitates the broader use of detailed chemistry in internal combustion engine (ICE) applications, supporting modern powertrain development needs.

Hernandez, Ignacio, Turquand d Auzay, Charles, Shapiro, Evgeniy, Shala, Mehmet, Borg, Anders, Seidel, Lars, Mauss, Fabian

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

Analysis of In-Cylinder Flow for Hybrid Gasoline Engine using High-Speed Particle Image Velocimetry

2026-01-0298

4/7/2026

To increase the thermal efficiency of a hybrid inline 4-cylinder direct injection engine, combustion promotion was carried out by enhancing the in-cylinder flow. The intake port and piston top shape were optimized using CFD. In-cylinder flow analysis in steady flow showed that the mean steady flow tumble ratio with the in-cylinder flow enhancement specification increased to 1.7 compared to 1.0 with the previous model and 1.4 with the early development specification. The limit engine speed, which is the engine speed at when the mean flow coefficient decreases due to the choke, and the mean steady flow tumble ratio with the in-cylinder flow enhancement specification were positioned on the trade-off line between the NA and the TC engine. In-cylinder flow analysis on the single-cylinder optical engine showed that the in-cylinder flow entering the cylinder smoothly flowed to the exhaust side, and the in-cylinder flow descending on the exhaust side was smoothly converted to the upward flow by the piston top. Thus, the tumble ratio with the in-cylinder flow enhancement specification in the latter half of the compression stroke increased from 1.0 to 1.7 compared to the early development specification. Turbulent analysis was performed by applying the time filter method, a turbulence decomposition method proposed by the authors, to the in-cylinder flow field. The turbulent kinetic energy with the in-cylinder flow enhancement specification in the latter half of the compression stroke increased by 21.9%. The flame structure was located in the corrugated flamelets region on the turbulent premixed diagram, and the combustion promotion effect by in-cylinder flow enhancement was expected. Evaluation of combustion characteristics on the metal engine showed that the initial combustion duration with the in-cylinder flow enhancement specification decreased by 2.3 deg., the main combustion duration decreased by 4.4 deg., and the time loss decreased by approximately 2%. Therefore, the indicated thermal efficiency increased from 41.9% to 42.2%, proving the concept of combustion promotion by in-cylinder flow enhancement.

Okura, Yasuhiro, Urata, Yasuhiro

Effect of Pre-Chamber Geometry on Methanol Cold-Start Combustion in an SI Engine

2026-01-0307

4/7/2026

Vehicle pollutant emissions are a major challenge in the development of internal combustion engines. To meet increasingly strict regulations, the automotive sector is exploring alternative fuels and lean-burn strategies. Methanol is gaining importance as a carbon-neutral fuel due to advances in green production technologies. Methanol, despite its potential for renewable production, faces severe limitations due to its inherent poor cold-start performance with conventional ignition systems. In this context, the present study aims to investigate the influence of pre-chamber ignition on cold-start combustion by using high-speed optical diagnostics to visualize flame propagation while simultaneously measuring in-cylinder pressure and engine performance. A major result concerns the significant cyclic variability of conventional spark ignition (SI) under cold-start conditions, which exhibits significant cyclic variability. Instead, passive pre-chamber ignition significantly enhances cold-start combustion stability, lowering CoV IMEP to below 3% at λ = 1.0 and sustaining stability under 5% even in ultra-lean conditions (λ = 1.6), where conventional SI operation fails. Flame visualization quantitatively confirms that this stability stems from distributed, multi-point ignition, which accelerates initial flame propagation by 3-4x compared to SI. These findings demonstrate that pre-chamber ignition can effectively overcome the traditional "cold-start" problem for methanol, enabling stable combustion from the first cycles. This provides an invaluable dataset for CFD model validation, as it captures a highly stable combustion process largely independent of the adverse thermal boundary conditions typical of cold start, thereby simplifying the modeling challenge.

Sementa, Paolo, Altieri, Nunzio, Tornatore, Cinzia

In-Situ Raman Measurements of Fuel Dilution of Lubricant Films in a Direct-Injection Spark-Ignition Engine

2026-01-0355

4/7/2026

To measure the fuel proportion within the lubricant film, an in-situ Raman spectroscopy technique was employed in a specially modified single-cylinder direct-injection spark-ignition engine. The engine block was engineered for optical access with a fused silica window, enabling a focused laser beam to probe the lubricant film on the engine liner under motoring conditions. The lubricant used was GTL8 base oil with ZDDP additive, and iso-octane was injected as a model fuel to study fuel-lubricant mixing. A calibration curve was established by recording Raman spectra of known mixtures of GTL8 oil and iso-octane. The Raman intensity ratio of the iso-octane peak to the oil peak was used as a quantitative indicator of fuel concentration. During engine operation, Raman spectra were acquired in real time, on a cycle-by-cycle basis, through the optical window. Upon iso-octane injection, its characteristic Raman peak appeared in the spectrum, and the intensity ratio was referenced against the calibration curve to estimate the fuel proportion within the lubricant film. Experimental results demonstrated that the iso-octane signal could be detected during and after injection and this allowed for real-time monitoring of fuel dilution dynamics. The main challenge encountered was high fluorescence from oil, which sometimes obscured the Raman peaks and complicated quantification. Despite this, the technique successfully demonstrated the feasibility of direct, in-situ, and real-time quantification of fuel dilution in engine lubricant films, providing a valuable tool for studying fuel-lubricant interactions under operating engine conditions.

Bolle, Bastien, Augoye, Kobi, Wong, Janet, Aleiferis, Pavlos, Hall, Jonathan, Bassett, Mike, Cracknell, Roger

A Helical Compression Spring Fracture under Impact Velocity in Pump Operation by Theoretical Study and FEA

2026-01-0271

4/7/2026

Helical compression springs have been used widely in various industries from automotive, aerospace and construction to electronics and medical devices. In the automotive industry, they appear in many places such as suspension, valvetrain, etc., as well in the discharge check valve of Gasoline Direct Injection (GDI) pump, which is the subject of study due to a recent fracture in lab testing. A theoretical study is conducted first to establish the equation governing spring dynamic motion under impact velocity, which can be in high magnitude with surging shock wave along spring axis. A new spring shock wave equation is developed for spring axial motion coupled with coil torsional effect. This newly derived shock wave equation has a broader term than the classic spring formula found in most engineering books. In this paper, it shows that the classic spring shock wave equation is only a special case for the general wave equation newly discovered. Then, a theoretical formula on spring shock wave propagation speed and natural frequency are presented, validated by a numerical simulation result by FEA on the spring natural frequency. Next, a FEA tool is employed to study the spring system under transient impact velocity, the spring dynamic stress at fracture location is obtained. It compares closely with the analytical approximate solution. Finally, a fatigue life assessment is performed, back up by the fractured part photo as well as the fatigue life cycles observed in testing. They are found in good agreement.

Pang, Michael L., Gunturu, Srinu, Norkin, Eugene

How higher-quality gasoline keeps modern engines CLEAN AND EFFICIENT

26AUTP03_03

3/1/2026

Gasoline direct injection (GDI) engines are the most common technology on American roadways in 2025, and soon, an industrywide gasoline quality standard will better reflect their unique operational needs. Here's why that's important. It's no secret that fuel economy has been one of the greatest driving forces of automotive evolution over the past several decades. As corporate average fuel economy (CAFE) standards have grown increasingly lofty, OEMs eke out new efficiencies from every area of the vehicle. One of those areas, of course, is the engine, and many OEMs have deployed gasoline direct injection (GDI) technology, which is becoming the most common engine technology on American roadways. But while GDI engines proliferate, varying fuel additization throughout North America has not necessarily kept pace with their unique needs and can, in fact, hinder those engines from meeting and sustaining their full fuel economy potential.

Blackburn, Brett

Influence of Lubrication Oil on Hydrogen Fuel-Share Combustion in a Conventional Medium-Speed Marine Diesel Engine

2026-01-5014

2/23/2026

Carbon-free fuels present a potential solution for achieving climate-neutral operation of marine engines. However, their availability is minimal at the moment, though a steady increase can be expected in the coming years. During this transition phase, engine concepts that offer conventional diesel operation and a partial blending of alternative fuels to substitute diesel become interesting. This can be achieved, for example, by blending hydrogen in the intake air of a diesel engine, known as hydrogen fuel-share. Due to the high reactivity of hydrogen, its use in engines is limited by abnormal combustion phenomena (e.g., pre-ignition, knocking combustion), which current research on pure gas engines has shown to be strongly promoted by lube oil reactivity. Building on these fundamental investigations, this paper examines the influence of lubricating oil on the combustion characteristics of a H2 fuel-share medium-speed diesel engine and quantifies the potential to increase the hydrogen share using a less reactive engine oil. For this purpose, single-cylinder engine tests were conducted and supported by 0D/1D simulations with GT-Power and Cantera. The engine was configured as a conventional medium-speed marine diesel, equipped with a hydrogen port fuel injection (PFI) system on the cylinder head. A thermally stable ester-based gas engine oil was used for reducing reactivity compared to a state-of-the-art mineral diesel engine oil. The results show reduced auto-ignition tendency during compression and a mitigation of backfire. An increase in average effective CO2 reduction of up to 17 percentage points is demonstrated, resulting in a total CO2 reduction of 39% on a standard load profile for main propulsion engines. These findings highlight that the choice of lubricating oil can play a key role in increasing the hydrogen share in H2 fuel-share diesel engines, thereby supporting the transition toward climate-neutral propulsion concepts.

Achenbach, Tobias, Meinert, Robert, Mahler, Kay, Kunkel, Christian, Rösler, Sebastian, Prager, Maximilian, Jaensch, Malte

CFD Simulation of Combustion and Emission Characteristics of Pure Spirulina Microalgae Biodiesel in a Single-Cylinder DI Diesel Engine

2026-28-0043

2/12/2026

In this study, the combustion and emission characteristics of a single-cylinder direct injection (DI) diesel engine fueled with Spirulina biodiesel along with diesel blends were examined using a combined CFD and thermodynamic simulation framework. Three test fuels, including pure diesel (D100), Spirulina biodiesel blends (B20 and B40), and pure Spirulina biodiesel (B100), were analysed at 1500 rpm under full load. In the first stage, CFD simulations were performed in ANSYS Fluent, where the Discrete Phase Model (DPM) was applied to capture spray atomization and droplet evaporation, while a non-premixed combustion model coupled with the RNG k-ε turbulence model was employed to resolve in-cylinder flow and heat release dynamics. Subsequently, the Diesel-RK software was utilised to predict engine performance and exhaust emissions based on compression ratios (18.5) and injection timings. Results from the CFD analysis revealed faster atomization and reduced ignition delay for biodiesel blends compared with pure diesel, supported by enhanced cylinder pressure development. Diesel-RK simulations indicated that Spirulina biodiesel blends (B20) generally improved brake thermal efficiency at higher compression ratios while increasing brake specific fuel consumption due to their lower calorific value. Emission analysis showed consistent reductions in CO, HC, and smoke capacity with higher biodiesel content, while NOx emissions exhibited a rising trend. The findings confirm Spirulina biodiesel (B20) as a viable renewable fuel and highlight simulation-driven strategies for optimising compression ratio and injection timing in CI engines..

Kumar, B Varun

Enhancing Combustion, Performance and Emission Profiles Using Kapok Methyl Ester Blends with Hydrogen

2026-28-0058

2/12/2026

This study investigates the potential of using a dual green alternative fuel combination, the one is hydrogen fuel and another one is biodiesel for enhancing the Performance, combustion and emission profile of a compression ignition engine. The kapok oil biodiesel was blended with Diesel in proportions of 20% (K20) and 40% (K40) by volume. The hydrogen gas was supplied at a constant flow of 4 liter per minute (LPM). The experimental fuels are neat diesel D100, K20 (80% Diesel and 20 % kapok methyl ester), K40 (60% Diesel + 40 % Kapok methyl ester), K20 + H4L (K20 with 4 LPM hydrogen) and K40+H4L (K40 with 4 LPM hydrogen). These test blends are investigated in a single cylinder direct injection CI engine under 0% to 100% load conditions at a fixed speed of 1500 rpm combustion, and emissions characteristic were evaluated and compared with base fuel. The outcomes indicated that the use of B20 and B40 blends without hydrogen led to reduced BTE because of their lower cetane number and calorific value. Additionally, higher viscosity of the blends resulted in increased BFSC. However, the introduction of hydrogen and the K20H fuel blend demonstrated notable emission improvements compared to conventional diesel, achieving reductions of 9–11% in unburned hydrocarbons, 5.3% in carbon monoxide, and approximately 8% in nitrogen oxides (NOₓ). These findings highlight the potential of K20H as a cleaner alternative fuel.

Anbarasan, B, M, Kumaresan, Balamurugan, S, Rajesh, Munnusamy

Research on Active Predictive Speed Control of Dual-Fuel Engine for Hardware Real-Time Applications

03-19-01-0004

2/9/2026

The present article proposes an active observation speed prediction control algorithm architecture for embedded applications, with the aim of addressing the problems of complex operating conditions, strong perturbations, and high control real-time requirements of high-pressure direct injection (HPDI) dual-fuel engines. A nonlinear speed prediction model with diesel and natural gas injection mass as inputs has been established, and the nonlinear model predictive control (NMPC) method is used to realize the optimized control of engine speed. In order to enhance the operational efficiency of the algorithm on the embedded platform, a system has been developed that includes an event triggering mechanism and a warm-start strategy. These mechanisms work in tandem to dynamically adjust the computation cycle. Additionally, a torque reduced-order expansion state observer (RESO) has been integrated to improve the accuracy of perturbation estimation and computational efficiency. The model-level experiments and hardware verification were carried out under the sudden load change operating condition and World Harmonized Transient Cycle (WHTC) test, respectively. The simulation results demonstrate that the proposed optimization strategy can effectively reduce the peak-to-peak value of speed control error to 118.73 rpm and shorten the stabilization time to 3.48 s. Furthermore, the tracking accuracies of the controller on the speed and torque targets in the hardware test reach 0.994 and 0.997, respectively, thereby substantiating the high accuracy and robust performance of the proposed algorithm.

Yang, Xinda, Li, Yunhua, Chen, Dongdong, Li, Yao, Zhang, Shutao, Zhao, Feiyang, Yu, Wenbin

Potential of a Hydrogen Fuel-Share Combustion Concept for a Conventional Medium-Speed Marine Diesel Engine

2026-01-5007

2/2/2026

To meet the International Maritime Organization’s (IMO) short-term greenhouse gas (GHG) reduction targets, partial decarbonization of the existing fleet, often powered by medium-speed diesel engines, is required. One approach for reducing CO2 emissions is to enrich the charge air with hydrogen to substitute diesel. However, hydrogen’s high reactivity can lead to combustion abnormalities such as backfire, pre-ignition, and knocking, thus limiting the feasible admixture rates. These challenges are particularly relevant in medium-speed diesel engines designed for high power output and efficiency at low rpm. While hydrogen fuel-share has previously been tested in small-bore engines at moderate loads, this study investigates the influence on combustion and achievable hydrogen admixture rates in a medium-speed, 4-stroke diesel engine operating with up to 30 bar net indicated mean effective pressure (net IMEP). To minimize retrofitting efforts and to preserve diesel performance, the investigations were conducted on a single-cylinder engine with representative design features of a conventional diesel engine: a high compression ratio, Miller valve timing, valve overlap, and a piston with deep valve pockets. The piston ring system is suited for heavy fuel oil (HFO) operation. Hydrogen was supplied via a port fuel injection (PFI) system. 0D/1D process simulations supplement the experimental data. Findings indicate that energetic hydrogen admixture rates of up to 43% are achievable at low loads, limited by an advancing start of combustion, and up to 15% hydrogen share at high loads, constrained by backfire. This results in an average CO2 reduction of ~22% on the E2 cycle for constant-speed main propulsion engines. Due to rising NOx emissions, the results are only applicable when meeting IMO Tier II limits with selective catalytic reduction (SCR). The results demonstrate that conventional medium-speed diesel engines are suited for hydrogen fuel-share operation and that CO2 reductions comparable to liquid natural gas (LNG) conversions are feasible.

Achenbach, Tobias, Meinert, Robert, Mahler, Kay, Kunkel, Christian, Rösler, Sebastian, Prager, Maximilian, Jaensch, Malte

Rolls-Royce pursues pure methanol for marine engines

26TOFHP02_05

2/1/2026

Rolls-Royce has successfully tested the world's first high-speed marine engine powered exclusively by methanol on its test bench in Friedrichshafen, Germany. The company began this engine-development journey six years ago when it gathered experts to determine what the future fuel of the maritime industry should be, according to Denise Kurtulus, senior vice president of global marine at Rolls-Royce. “For us, it's clear. It's methanol,” she said. Rolls-Royce worked with industry partners as part of the joint project meOHmare, which is funded by the German Federal Ministry for Economic Affairs and Energy. Injection system specialist Woodward L'Orange and the WTZ Roßlau technology and research center contributed their expertise. Their goal was to not only develop a comprehensive concept for a CO2-neutral marine engine based on green methanol, but also to run it on the test bench by the end of 2025.

Gehm, Ryan

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

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

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

Performance Optimization of 2 Cylinder Flex Fuel Engine for Small Commercial Vehicle – A STEP TOWARDS SUSTAINABILITY

2026-26-0119

1/16/2026

Increasing ethanol blending in gasoline is significant from both financial (reducing dependency on crude oil) and sustainability (overall CO2 reduction) points of view. Flex Fuel is an ethanol-gasoline blend containing ethanol ranging from 20% to 85%. Flex Fuel emerges as an exceptionally advantageous solution, adeptly addressing the shortcomings associated with both gasoline and ethanol. Performance optimization of Flex Fuel is a major challenge as fuel properties like knocking tendency, calorific value, vapour pressure, latent heat, and stoichiometric air-fuel ratio change with varying ethanol content. This paper elaborates on the experimental results of trials conducted for optimizing engine performance with Flex Fuel for a 2-cylinder engine used in a small commercial vehicle. To derive maximum benefit from the higher octane rating of E85, the compression ratio is increased, while ignition timing is optimized to avoid knocking with E20 fuel. For intermediate blends, ignition timing is suitably interpolated. Fuel injection pressure is increased to address the higher fuel flow requirement, and a fuel heater is added to address cold starts with E85 fuel. Ethanol content detection is done through software, and by suitable interpolation, fuelling and ignition timing are optimized for the entire range of Flex Fuel in a single calibration file. Engine performance with E20 & E93 fuel is optimized considering all mechanical and thermal limits of the engine through various iterations. The experimental results are analysed using the first principle method.

Kulkarni, Deepak, Malekar, Hemant A, Upadhyay, Rajdip, Katkar, Santosh, Undre, Shrikant

Combustion Noise Quality Improvement in a Common rail Diesel Engine at Low Idle using Taguchi DOE

2026-26-0329

1/16/2026

Noise quality at idle condition is an important factor which influences customer comfort. Modern diesel engines with stringent emission norms together with fuel economy requirements pose challenges to noise control. Common rail engine technology has advantage of precise fuel delivery and combustion control which needs optimization to achieve the conflicting requirements of noise, emission and fuel efficiency. Engine noise at low idle condition is dominated by combustion noise which depends on rate of pressure rise inside the cylinder during combustion. The important parameters which influence cylinder pressure rise are fuel injection timing, pilot injection quantity and its separation, rail pressure and EGR valve position. The study on effect of these parameters at varying levels demand large no of experiments. Taguchi design of experiments is a statistical technique which can be used to optimize these parameters by significantly reducing no of experiments needed to achieve the desired results. These five CR parameters are varied at five different levels using an L25 Taguchi orthogonal array and noise measurements are conducted. The results of experiment have indicated that rail pressure has the highest effect on noise quality with 5dBA difference between the lowest and highest level of rail pressure. The second most significant parameter is pilot quantity with 3 dBA improvement by introducing pilot injection and the quantity of pilot injection needs to be kept minimum. Main injection timing has the potential of 1dBA and EGR valve position and pilot separation has very less influence. Engine calibration is optimized based on above inputs to meet the emission requirements and with the optimized calibration noise is improved by 5dBA at low idle

P, Priyadarshan, Chavan, Amit, A, Kannanswamy, Patil, Sandeep, Chaudhari, Vishal V

Development of a CNG-Diesel Dual Fuel Tractor with Mechanical Fuel Injection System

2026-26-0114

1/16/2026

Identification of renewable and sustainable energy solutions remains a key focus area for the engine designers of the modern world. An avenue of research and development is being vastly dedicated to propelling engines using alternate fuels. The chemistry of these alternate fuels is in general much simpler than fossil fuels, like diesel and gasoline. One such promising and easily available alternate fuel is compressed natural gas (CNG). In this work, a 3-cylinder, 3-liter naturally aspirated air-cooled diesel engine from the off-highway tractor application is converted into a CNG Diesel Dual fuel (CNG-DDF) engine. Part throttle performance test shows the higher NMHC and CO emissions in CNG-DDF mode which have been controlled by an oxidation catalyst in C1 8-mode emission test. A comparative performance shows that the thermal efficiency is up to 2% lower with CNG-DDF with respect to diesel. However, it has shown the benefit of 44% in Particulate Matter, while retaining the same NOx + NMHC levels as the baseline diesel engine. The cycle average CO emission has been found to increase by 6%. Average exhaust gas temperature has been found to be lower by up-to 54°C with CNG-DDF. To control the particulate and HC levels of the baseline NA engine, the CNG injection has been confined from 20% to 85% engine loads, across all engine speeds. The peak firing pressure and in-cylinder temperature are lower by ~3% and ~7%, and the SoC got retarded by max 4°CA with CNG-DDF which is in-agreement with drop in thermal efficiency. The outcome from the engine dyno level testing has been successfully validated through the tractor testing.

Choudhary, Vasu, Mukherjee, Nalini, Kumar, Sanjeev, Tripathi, Ayush, Nene, Devendra

Technologies and Strategies for High Brake Thermal Efficiency Gasoline Engine to Meet the Future CO ₂ Emission Targets in India

2026-26-0072

1/16/2026

The Indian automobile industry is experiencing a significant shift, propelled by environmental necessities and national climate obligations set at the CoP26 summit, aiming for a 45% decrease in CO₂ emissions by 2030 and reaching carbon neutrality by 2070 [1]. Transportation continues to be a significant source of air pollution; consequently, India is enhancing its regulatory frameworks with BS VI Stage 2 regulations, CAFE Phase III norms set for 2027, and CAFE Phase IV by 2032 [2]. Furthermore, the transition from MIDC to WLTP driving cycle is meant to increase the accuracy of the efficiency and emissions assessments [2]. To comply to these upcoming regulations, the automotive industry is moving toward producing high efficiency engines in India. A naturally aspirated (NA) 1.5L, 4-cylinder inline gasoline engine was selected from Indian market for this study. Maximum Brake Thermal Efficiency (BTE) of this engine is around 37%. Assessment of new technologies were performed by implementing them stepwise to see the impact on BTE. A well calibrated 1D GT-SUITE model was considered from FEV database to perform the simulation-based approach to increase the BTE by improving the stroke/bore (s/B) ratio, increasing the compression ratio, implementing Atkinson cycle with variable valve timing (VVT) / variable valve lift (VVL) optimization, and charge motion refinement for optimal in-cylinder combustion. Low temperature cooled EGR (TEGR < 70°C) and pre-catalyst pick-up distributed EGR strategies were simulated to improve the combustion stability and pumping loss for BTE improvement. Friction losses were further minimized by implementing the polished surfaces, electrification of auxiliary components, and other advanced surface treatments. Advanced technologies including Dual Port Fuel Injection (Dual PFI) system, high energy ignition system with thermal swing coatings, and system designed to operate with highly diluted mixture are required to achieve maximum BTE. These technologies would also be explored in this study. This paper also covers the rivals' restrictions put on engine geometry and number of cylinders concerning possible max. BTE level with which the engine can achieve. With the completed study, the efficiency step walk document indicated BTE improvement from each technology step to achieve a target max. BTE for the engine.

Garg, Shivam, Fischer, Marcus, Emran, Ashraf, Jagodzinski, Bartosch, Franzke, Bjoern

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