Browse Topic: Engine efficiency

Items (1,061)

Numerical Analysis of Pre-Ignition Factors in Hydrogen Engines

2026-01-0740

7/1/2026

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

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

Synergistic Integration of Advanced Combustion and Air-Path Technologies to Maximize Internal Combustion Engines Efficiency in Hybrid Applications

2026-01-0733

7/1/2026

This paper assesses the efficiency limits of light-duty vehicle propulsion systems based on reciprocating internal combustion engines (ICE) in the current state of the art and in the next five-year horizon, considering their combination with technologies such as electric turbocharging and hybridization, while excluding plug-in hybrid configurations so that fuel remains the primary onboard energy source. A systematic methodology is applied to evaluate the influence of key variables—heat transfer, air–fuel ratio, and compression ratio—on engine performance, integrating these variations into a simulation model to capture their interactions and effects. The resulting parametric study enables the generation of new engine maps that exploit synergies between parameters and enhance the prediction of engine behaviour across different operating conditions, forming the basis for assessing potential advancements in hybrid powertrain architectures. These maps are then used to define performance expectations for hybrid vehicles, identifying optimal parameter combinations to guide future technology development and improve efficiency in hybrid powertrain design. The proposed powertrain architectures are integrated into a representative vehicle model, considering two vehicle typologies: a compact passenger car and a sport utility vehicle (SUV). To quantify the potential fuel-consumption benefits, an intelligent energy-management algorithm is implemented to supervise and optimize system operation over a WLTC driving cycle. The results indicate that the proposed configurations can achieve fuel-consumption reductions exceeding 20%, demonstrating the effectiveness of both the powertrain designs and the control strategies. Overall, the findings highlight the significant efficiency potential of advanced ICE-based propulsion systems when combined with near-term technologies such as electric boosting and hybridization, confirming the viability of these improvements and providing a robust basis for future hybrid vehicle development focused on maximizing energy efficiency in transportation.

Pla, Benjamin, Dolz, Vicente, Serrano, Jose R., Gómez-Vilanova, Alejandro, Oliva, Fermin, Cardenas, Maria, Ariztegui, Javier

Defining and Measuring Factors Affecting Helicopter Turbine Engine Power Available

ARP1702B (Current)

6/29/2026

This SAE Aerospace Recommended Practice (ARP) identifies and defines a method of measuring those factors affecting installed power available for helicopter powerplants. These factors are installation losses, accessory power extraction, and operational effects. Accurate determination of these factors is vital in the calculation of helicopter performance as described in the RFM. It is intended that the methods presented herein prescribe and define each factor as well as an approach to measuring said factor. Only basic installations of turboshaft engines in helicopters are considered. Although the methods described may apply in principle to other configurations that lead to more complex installation losses, such as an inlet particle separator, inlet barrier filter (with or without a bypass system), or infrared suppressor, specialized or individual techniques may be required in these cases for the determination and definition of engine installation losses. Some rotorcraft may use an alternate source of propulsion system power to supplement engine output shaft power delivered. If RFM performance includes the contribution of a Supplemental Power Unit (SPU), then the installed power available of the SPU should also be defined and measured, for which the power loss factors and methods described in this document may be applicable.

S-12 Powered Lift Propulsion Committee

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

Potential of ORC-Based Waste Heat Recovery in Conventional and Hybrid Heavy-Duty Powertrains

2026-37-0018

6/9/2026

Heavy-duty vehicles significantly contribute to greenhouse gas emissions and urban air pollution, especially during cold-starts and transients when engine and aftertreatment efficiencies drop. Waste heat recovery (WHR) via Organic Rankine Cycle (ORC) systems offers a practical solution to improve fuel efficiency and cut CO₂ in real-world heavy-duty operations. This study examines ORC-based WHR integration into conventional and hybrid powertrains of an Isuzu FTR850 truck, analyzing four configurations: Shell-and-Tube or Plate heat exchangers with simple or regenerative ORC layouts. For hybrids, it compares two engine sizes and energy management strategies: an optimized fuzzy logic approach versus constant-power operation to enhance exhaust heat recovery. A validated quasi-static simulation framework is used to predict fuel consumption and exhaust properties over representative duty cycles. 2D performance maps using exhaust temperature and mass flow as inputs are used to model the WHR under off-design conditions. Results show that the recovery of waste heat WHR depends on the hybridization level and strategy. Conventional powertrains benefit most from Shell-and-Tube exchangers, recovering ~2 kWh of electrical energy per 8-hour cycle and reducing fuel consumption by 0.5%. Hybrid setups recover up to 3.9 kWh from exhaust gases with a simple layout coupled with a Shell-and-Tube heat exchanger under constant-power control. Electricity is used to support onboard auxiliaries and battery charging, further lowering fuel demand (-44%) and emissions. Finally, a multi-objective optimization was performed to exploit the synergy between hybridization and WHR while maintaining acceptable payload and battery operating conditions.

Donateo, Teresa, Morrone, Pietropaolo

Potential of an In-Cylinder Pressure–Based Combustion Control for Compression Ignition Aviation Engines Operated with Sustainable Aviation Fuels

2026-01-5028

5/29/2026

The aviation industry represents a significant greenhouse gas emitter and aims to reduce net CO2 emissions to zero by 2050. The deployment of sustainable aviation fuel (SAF), alongside measures such as increasing engine efficiency and enhancing ground handling processes, represents a key driver to reach this ambitious goal. SAF exhibits significantly different physical and chemical properties compared to conventional kerosene. The corresponding fuel specification (ASTM D7566 [1]) currently only defines fuel parameters relevant for the use in jet engines. To assess the suitability of SAF for the use in compression ignition (CI) aviation engines, a collaborative project was conducted at TU Wien—Institute of Powertrain and Automotive Technology, together with Austro Engine. ASTM D7566-certified fuels like Hydrotreated Vegetable Oil (HVO), Fischer–Tropsch–Kerosene (FTK), and Alcohol-to-Jet (AtJ) have been investigated on the engine test bench at TU Wien. The core contribution of this study is the experimental evaluation of a real-time capable in-cylinder pressure–based combustion control strategy that enables fuel-flexible and optimized CI engine operation across a wide range of SAF while accounting for mechanical constraints such as peak cylinder pressure and pressure rise rate. To evaluate the potential of such a control system, optimized engine operation was compared to operation with conventional ECU (Engine Control Unit) mapping. Furthermore, the influence of such a real-time combustion process optimization on critical emissions like NOx or soot has been evaluated. Through the implementation of an in-cylinder pressure–based combustion control, a considerable fuel-saving potential could be demonstrated across the entire fuel range. As combustion phasing is optimized toward early crank angle positions, a slight increase in NOx, with a corresponding decrease in soot is observed. Additionally, the use of automotive, piezoresistive pressure sensors was examined regarding a potential serial application. It has been shown that piezoresistive sensors (standard serial parts—calibrated for automotive application) are well-suited for determination of combustion phasing, while in-cylinder peak pressure and its position can only be determined with insufficient accuracy.

Kleissner, Florian, Hofmann, Peter

Effect of Burning Biomass Fuel Cyclohexanol on Diesel Engine Performance

2026-99-1708

5/22/2026

Against the backdrop of growing global demands for energy sustainability and stricter emission regulations for diesel engines, this study investigates the performance implications of incorporating cyclohexanol—a renewable oxygenated fuel—into diesel fuel blends. Using a marine medium-speed diesel engine as the experimental platform, the research systematically evaluates engine performance and emission characteristics across a range of cyclohexanol-diesel blend ratios under low, medium, and high load conditions. Experimental findings reveal multifaceted effects of cyclohexanol blending on engine operation. Combustion of the blended fuels enhances the engine’s dynamic performance, particularly under medium and high loads, where the maximum in-cylinder burst pressure exhibits a noticeable increase. This improvement is attributed to cyclohexanol’s oxygen-carrying capacity, which promotes more vigorous and sustained combustion reactions. In terms of emissions, increasing the proportion of cyclohexanol in the fuel blend leads to significant reductions in soot and carbon monoxide (CO) emissions, reflecting the cleaner-burning properties of the oxygenated component. However, this is accompanied by an uptick in nitrogen oxide (NOx) emissions, likely due to the elevated combustion temperatures generated by the more efficient fuel oxidation process. From an economic perspective, cyclohexanol blending at consistent load levels induces a postponement in the crank angle at which peak heat release occurs during combustion. This temporal shift prolongs the effective combustion duration, enabling more complete fuel utilization within the cylinder. Consequently, fuel consumption rates decrease, and overall engine efficiency improves, highlighting the potential of cyclohexanol blends to enhance operational economy in marine propulsion systems. In summary, this study underscores the complex trade-offs associated with cyclohexanol-diesel blends: while they offer tangible benefits in power output, fuel efficiency, and reduced particulate emissions, managing the increase in NOx emissions remains a critical challenge. The results provide a foundational framework for advancing biofuel applications in marine engines, emphasizing the need for integrated emission control strategies to optimize the balance between performance and environmental sustainability.

Chen, Ke, Yang, Chenxi, Wang, Yibin, Fan, Jinyu, Liu, Yuchen, Ye, Zixiao, Huang, Jialiang

Experimental Study of Knock Resistance Offered by Direct Water Injections in a Single-Cylinder Spark Ignition Engine

03-19-02-0011

4/11/2026

Stochastic end-gas autoignition in spark ignition (SI) engines, commonly called “knock,” limits attainable engine efficiencies. Multiple pathways to extend SI engine operation into knock-limited regions have been studied, including direct water injection (DWI). This study employs single-cylinder engine experiments with a centrally mounted water injector to investigate the knock resistance offered by compression stroke water injections, which, through incomplete mixing, can thermally stratify the cylinder. In SI, thermally stratifying injections are expected to forcibly widen the cylinder temperature distribution by preferentially cooling the cylinder periphery. The end-gas is in the cylinder periphery. A cooler end-gas would result in longer ignition delays, thus providing knock resistance. The difference between intake temperature required to match knock-limited CA50 and a baseline intake temperature at the load of 8 bar IMEPg (gross indicated mean effective pressure) was used to quantify the “effective charge cooling” for the injection timings studied. A higher positive value for the effective charge cooling implies higher knock resistance. Effective charge cooling values for early compression stroke injection timings (−180° to −120° aTDC) were observed in the range of ~35−45 K. Later compression stroke and intake stroke injection timings displayed effective charge cooling values in the range of ~5−35 K and ~0−20 K. A compression stroke injection timing sweep was performed at a load of 6 bar IMEPg while holding the spark timing, intake temperature, and water mass constant to study the effect of injection timing on the combustion process. Although CA50 advanced while delaying the injection timing (−180° to −80° aTDC), post-CA50 burn durations stayed nearly constant, a behavior consistent with the presence of thermal stratification. Thus, it was concluded that injection timings that heterogeneously cool the cylinder provide higher knock resistance compared to bulk cooling.

Datar, Aditya, Vedpathak, Kunal, Gainey, Brian, Lawler , Benjamin

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

Upstream Oxygen Sensor Signal Improvement Using the DFSS and Virtual Validation Approach

2026-01-0486

4/7/2026

Combustion stability and emission control remain key challenges for gasoline engines, requiring robust oxygen sensing strategies. The primary function of the upstream exhaust oxygen sensor is to detect the oxygen concentration in exhaust gas for accurate air–fuel ratio control. However, poor signal visibility from individual cylinders across engine speeds can lead to improper combustion prediction and reduced engine efficiency. This work applies a Design for Six Sigma (DFSS) approach to optimize the upstream oxygen sensor configuration in a 2.0 L four-stroke gasoline engine. Conventionally, sensor placement is completed by iterative testing and calibration, which is both time-consuming and cost intensive. The DFSS framework uses input, output, control, and noise factors. Exhaust gas mass flow rate from engine cylinders at different speeds is treated as the input, while the detected oxygen mass fraction is the output. Design parameters such as pipe length, pipe diameter, sensor orientation, insertion depth, and location are considered control factors. Sensor element position and ambient temperature serve as noise factors, as they cannot be controlled directly by the engineer. The analysis is performed using three-dimensional computational fluid dynamics (CFD) and confirmed through Design of Experiments (DoE) simulations. The optimized configuration achieved improved sensor signal stability and cylinder visibility, enabling more reliable combustion control. This structured approach demonstrates how virtual analysis combined with DFSS principles can guide robust oxygen sensor placement strategies, reducing validation effort while enhancing engine efficiency and emissions performance.

Dixit, Manish, Raja, Vinayak, Annabattula, Pallavi

Experimental Study of Hydrogen Combustion in Argon-Oxygen Mixture Using an Optical Engine

2026-01-0328

4/7/2026

The Argon Power Cycle (APC) is an emerging high-efficiency combustion technology for internal combustion engines. In APC, the conventional air-based working fluid is replaced with an inert argon gas. This substitution inherently increases engine efficiency through thermodynamic properties of argon, in particular a high adiabatic factor ?? ~1.67. A hydrogen-fueled APC engine offers the potential for highly efficient zero emission combustion by also eliminating nitrogen oxide (NOx) formation. In the present paper, hydrogen combustion is studied in an optical heavy-duty research engine, with the objective of providing the first visualization of H2 combustion in an argon–oxygen mixture. A comparative analysis of high-speed optical imaging and in-cylinder pressure measurements is conducted for two different modes: 1) conventional air operation and 2) argon-oxygen mixture operation. The high-speed images reveal a distinctly different combustion process between the two operating modes. The main results of the study are as follows: 1) The cylinder peak temperature during compression, estimated from cylinder pressure, increases from approximately 800K (air) to 1200K (argon-oxygen). 2) Abrupt hydrogen pre-ignition was observed for the argon-oxygen mixture, leading to strong pressure oscillations. In contrast, for hydrogen-air combustion, the mixture was ignited by the spark without pre-ignition. 3) The initial heat release was significantly higher in the argon-oxygen mixture yielding a pressure rise in a few crank angle degrees (CAD) in contrast to 5-10 CAD for the air mixtures. 4) Extremely lean hydrogen combustion was observed for the argon-oxygen case.

Kapp, Joakim, Cheng, Qiang, Kaario, Ossi, Vuorinen, Ville

A Quantitative Approach for Mapping and Assessing Diesel Particulate Filter Regeneration Events in Diesel Engines

2026-01-0377

4/7/2026

Regeneration of diesel particulate filters (DPFs) is crucial for maintaining the performance of diesel engines and minimizing harmful particulate matter (PM) emissions from exhaust. However, conventional regeneration strategies often suffer from incomplete soot removal and inefficient monitoring. These issues lead to increased exhaust back pressure, reducing engine efficiency, and potentially damaging the particulate filter. In this paper, an approach is proposed for mapping and quantifying the real-world DPF regeneration process for diesel engines complying with the stringent emission standards. We introduce a novel metric, the differential pressure drop percentage (DPDP), to detect regeneration events and quantify soot burn quality. The proposed method utilizes real-time sensor data obtained through the vehicle’s On-Board Diagnostics (OBD) system. The algorithm processes sensor data and robustly maps the regeneration quality. The performance of regeneration event detection and soot burn quality has been validated based on diagnostic trouble codes (DTCs) raised by the engine control unit (ECU). Our proposed method demonstrates that predictive maintenance can be used to manage strategies for diesel exhaust after-treatment systems, which can effectively reduce increased maintenance costs and operational downtime.

Bagga, Harleen Kaur, Nagare, Mukund B., Patil, Bhushan D., Ravishankar, Hariharan, Melapudi, Vikram, Vanderheide, Craig, Patil, Abhijit

Ultra-Low NOx Technologies for Heavy-Duty Applications with Reduced Total Cost of Ownership

2026-01-0294

4/7/2026

The utilization of gasoline engines in heavy-duty vehicles for the purpose of continental transportation is in direct competition with conventional diesel engines. It’s imperative that the operating performance of the gasoline engine is equivalent to the diesel engine, and that the gasoline engine shows efficiency benefit to both cost segments, the product manufacturing costs and total cost of ownership (TCO). The 11.6-liter gasoline engine developed has been designed and applicated in such a way that it operates at a stoichiometric combustion air ratio (λ = 1) across the entire engine map range without exception. In combination with external exhaust gas recirculation (EGR) this strategy does not result in a substantial decrease in the absolute NOx concentration in raw emissions compared to the diesel engine with 15.0-liter displacement, but it facilitates the cost-efficient utilization of the three-way catalyzer as the main exhaust aftertreatment system, thereby reducing NOx emissions to the detection limit. This reduction is necessary for adherence to the stringent future emission standards for heavy trucks that are being established by the U.S. regulatory authorities (EPA; CARB) for model years commencing in 2027. In addition to the stoichiometric operating strategy, the engine features an innovative combustion chamber geometry, including a high compression ratio, high EGR compatibility within the real engine operating range, and an optimized crankshaft drive. This already tested technology package is now being applied to heavy-duty engines, proving its scalability and effectiveness. Its application to heavy-duty engines not only promises significant production cost savings but also ensures compliance with future emission regulations. By integrating high EGR rates and high compression ratio, the engine achieves optimal combustion efficiency, thereby minimizing emissions without compromising performance. The engine efficiency is demonstrated by its brake thermal efficiency of 43.1% and an extended map range with a specific consumption of less than 200 g/kWh. In a real heavy-duty driving cycle, the average consumption is 228 g/kWh (vs. 217.5 g/kWh), resulting in a significant reduction in total operating costs on the American market using gasoline as fuel.

Medicke, Mario, Arnold, Thomas, Bohme, Jan, Krause, Matthias, Leesch, Mirko

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

Investigation of Flame Speed Effects towards Knock Suppression in a Boosted Spark-Ignited Engine Using 1-D Modeling

2026-01-0311

4/7/2026

To combine high efficiencies and low pollutant emissions, engine manufacturers have developed downsized spark-ignited (SI) engines in light- and medium-duty applications utilizing charge boosting and high compression ratio. While these techniques have proven effective, abnormal combustion such as auto-ignition and knock present a challenge and an important limitation towards high efficiencies. In this work, simulations have been utilized for knock onset predictions as well to provide relevant insights and trends of engine and fuel parameters including flame speed on auto-ignition. A one-dimensional (1-D) GT-Power model was utilized in this study with a semi-predictive flame propagation model and kinetic mechanism solver to isolate the flame propagation rate on auto-ignition and knock. This work presents a comprehensive study of the laminar flame speed (LFS) effect on combustion at knocking conditions in a high compression ratio long stroke engine (LSE) fueled by propane. Knock onset and index from GT-Power as well as cylinder pressure were compared, as well as pressure-temperature trajectories and Borghi-Peters diagrams, while changing LFS via a multiplier at fixed ignition timing, fixed combustion phasing and knock-limited spark advance (KLSA). Moreover, cycle-to-cycle variability (CCV) was modeled through GT-Power. Results exhibited consistent trends at each condition, showing a significant importance of combustion phasing on knock onset and index. High flame speed displayed a reduction in knock index at fixed combustion phasing and KLSA conditions as well as a decrease in CCV, even eliminating knock onset at extreme LFS values, thus highlighting the benefits of faster flame speed in SI combustion with respect to engine efficiency and knock avoidance.

Douvry-Rabjeau, Julien, DelVescovo, Dan

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

Flame Velocity and Combustion Behaviour of Ammonia–Hydrogen Blends: A Combined Experimental and Numerical Study

2026-01-0320

4/7/2026

Ammonia is emerging as a promising energy vector for decarbonising the maritime sector. However, its low flame speed can lead to incomplete combustion, reduced engine efficiency, and increased emissions of unburned ammonia (NH3). Blending hydrogen with ammonia helps to address these issues, but the fundamental combustion characteristics of such mixtures remain insufficiently understood. This study examines the combustion dynamics of an NH3–H2 blend containing 30% hydrogen at 3 bar initial pressure. Experiments were performed in a 1.2 L optically accessible constant-volume combustion chamber fitted with a wall-mounted surface spark plug. High-speed shadowgraph imaging with 6,000 fps captured the flame evolution throughout the combustion process. The pressure and temperature values were monitored using piezoresistive pressure transducers and K-type thermocouples. Combustion times and flame extensions were extracted via post-processing of flame images using custom MATLAB algorithms. The combustion process was examined from the initial start to a diameter of 60mm. Complementary CFD simulations were carried out in CONVERGE using the C3MechV3.5 chemical mechanism. To match the experimental conditions, the numerical studies were conducted at an ambient pressure of 0.3 MPa and an equivalence ratio of 1.0. The model predicted flame propagation times accurately, achieving an average relative error of 2.95% and an R2 value of 0.991. A third-order polynomial correlation was derived to predict instantaneous flame diameter as a function of time, enabling interpolation for intermediate combustion stages for both simulation and experimental results. Error analysis indicated that the model achieved its best performance for medium-sized flames (30–45 mm) but exhibited larger discrepancies at the smallest and largest diameters. Nevertheless, within the 20–60 mm range, deviations remained between −9.5% and +3.4%.

Bodur, Tuna Murat, Bowling, William, La Rocca, Antonino, Cairns, Alasdair

Development and Testing of a Concentric Tube Camshaft for Continuous Adjustment of Intake Valve Duration and Timing in Otto and Miller Cycle Operations

03-19-02-0010

4/1/2026

The development of technologies capable of expanding the operational flexibility of internal combustion engines—particularly through advanced valve actuation strategies—has become essential for improving energy efficiency and reducing exhaust emissions. This work presents the design, manufacturing, and experimental evaluation of a novel, mechanically simple, and low-cost valve control system intended for spark-ignition engines originally designed to operate under the Otto cycle. The proposed innovation, designated VVT-D (Variable Valve Timing—Duration), introduces continuous and independent control of intake valve opening duration using a concentric tube camshaft architecture. Unlike conventional variable valve timing systems limited to phase control, the VVT-D concept enables continuous transition between Otto- and Miller-equivalent operating conditions by modulating intake valve duration as a function of engine load. This approach allows engine load control via Late Intake Valve Closing (LIVC), partially or fully eliminating intake throttling (dethrottling) and thereby reducing pumping losses, particularly under low- and medium-load conditions. The system was implemented in a Volkswagen EA211 1.0 TSI engine and evaluated on an engine dynamometer under torque-matched operating conditions. Experimental results demonstrated proper system functionality, mechanical robustness, and effective load modulation capability through intake valve duration variation. Under Miller-equivalent operation, a reduction of approximately 15.6% in brake-specific fuel consumption (BSFC) was observed relative to conventional throttled Otto cycle operation at partial load. These results indicate that the proposed VVT-D system provides meaningful improvements in overall engine efficiency while preserving the original engine architecture and offering a cost-effective alternative to fully variable or purely hydraulic valve actuation systems.

Alvares, Gabriel Coelho Rodrigues, Woiski, Emanuel Rocha, dos Santos, Paulo Sergio Barbosa, Kashani, Masoud Ghanbari, Gasche, José Luiz

Intelligent Steering System to Improve Fuel Efficiency in Heavy Duty Vehicles

2026-28-0103

2/12/2026

In commercial vehicles, conventional engine-driven hydraulic steering systems result in continuous energy consumption, contributing to parasitic losses and reduced overall powertrain efficiency. This study introduces an Electric Powered Hydraulic Steering (EPHS) system that decouples steering actuation from the engine and operates only on demand, thereby optimizing energy usage. Field trials conducted under loaded conditions demonstrated a 3–6% improvement in fuel economy, confirming the system’s effectiveness in real-world applications. A MATLAB-based simulation model was developed to replicate dynamic steering loads and vehicle operating conditions, with results closely aligning with field data, thereby validating the model’s predictive accuracy. The reduction in fuel consumption directly translates to lower CO₂ emissions, supporting regulatory compliance and sustainability goals, particularly in the context of tightening emission norms for commercial fleets. These findings position EPHS as a cost-effective and scalable solution for improving vehicle efficiency and environmental performance. Furthermore, the study highlights the future potential of transitioning to fully electric power steering systems (Full EPS), which not only promise additional efficiency gains but also enable seamless integration with Advanced Driver Assistance Systems (ADAS), laying the foundation for enhanced safety, automation, and intelligent vehicle control in next-generation commercial vehicles.

T, Aravind Muthu Suthan, Mani, Kishore, Ayyappan, Rakshna, D, Senthil Kumar, S, Mathankumar

Computational Fluid Dynamic and Fatigue Analysis of Turbocharger Turbine Wheel

2026-28-0070

2/12/2026

Turbochargers are essential for improving engine efficiency by compressing air and delivering it to the engine at higher pressure, thereby increasing power output. The turbine wheel in a turbocharger operates under severe mechanical and thermal stresses, making it highly susceptible to fatigue failure, which can occur even under conditions below the rated operating load. To ensure long-term reliability, detailed analysis of the turbine’s fatigue life is essential. This study combines computational fluid dynamics with fatigue analysis to predict the performance and lifespan of a turbocharger's turbine wheel, with a focus on Inconel alloys known for their durability in extreme conditions. A numerical mesh analysis, employing 1,165,610 nodes, was conducted to achieve convergence for both temperature and stress evaluations, leading to the selection of a 2 mm mesh size. Pressure contours at the turbine-fluid interface revealed a pressure range between 1.09 and 1.05 bar, with most of the turbine maintaining a temperature of 700°C, indicating an isothermal condition. Fatigue life predictions using the Geber model, effective for ductile materials, highlighted localized reductions in life expectancy around the blade tip, while most components maintained a factor of safety between 3 and 4, with a maximum of 15. Considering creep effects at 700°C, the turbine's safe operational life was estimated at 591 days. These findings were used to recommend critical design modifications to enhance the turbine’s durability and performance.

Chelladorai, Prabhu, Balakrishnan, Navaneetha Krishnan, G, Naresh, T J, Sreejaun

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

Corrosion Behavioral Study of Sintered Materials with Ethanol-Blended Fuels

2026-26-0277

1/16/2026

The increasing adoption of ethanol-blended fuels, such as E20 (20% ethanol and 80% gasoline) and E85 (85% ethanol and 15% gasoline), necessitates a comprehensive understanding of their compatibility with automotive engine components to ensure durability and operational reliability. Fuel compatibility is particularly critical for components in direct contact with ethanol-rich fuels, as improper material selection or insufficient testing can lead to corrosion, material degradation, and compromised engine performance. This study focuses on evaluating the behavior of sintered materials extracted from potential fuel-contact part of automotive engine when exposed to E20 and E85 fuels. Testing was conducted in accordance with the SAE J1747 standard, which provides a systematic approach for assessing corrosion resistance and material degradation in fuel environments. Following the exposure tests, post-test evaluations included visual inspection to identify surface changes and Scanning Electron Microscopy (SEM) examination to characterize corrosion mechanisms at the microscopic level. Results showed significantly higher corrosion rates, highlighting their susceptibility to ethanol-induced degradation. The study provides valuable insights into the corrosion behavior of sintered materials and underscores the importance of rigorous material selection and testing protocols to ensure engine compatibility with advanced ethanol-blended fuels. These findings can guide the development of more durable and efficient engine systems for future fuel applications.

Karthikeyan, C., Venugopal, Sivakumar, Gopalan, Vijaysankar

A Computational Approach to Fretting Wear Prediction of Steel Gaskets under Thermo-Mechanical Load Using Archard’s Wear Model

2026-26-0455

1/16/2026

Internal Combustion Engine (ICE) is the heart of an Automobile. The failure of any critical component of the ICE engine will directly affect the performance of the vehicle. The gaskets are among the many vital parts of an IC engine that are essential in ensuring appropriate sealing to prevent gas and liquid leakage and maintain optimal engine efficiency. Engines use a variety of gasket types to accommodate various sealing requirements. Among them the exhaust manifold gaskets are one of the critical gasket elements in ICE engines. Exhaust Gasket acts as a seal between cylinder head and extremely hot exhaust manifold, which prevents the leakage of hot exhaust gases produced during typical engine operating condition. The gaskets are crucial components because they endure extremely high mechanical loads from the exhaust manifold sliding and banana-shaped bending brought on by thermal expansion, as well as extremely high thermal loads from the high exhaust gas temperatures, which are more than 800°C. These gaskets are additionally subjected to extremely high bolt loads. As the gaskets are made of steel materials, due to the above Thermo-Mechanical loads, there are very high chances for wear out of the gaskets, which affects the performance characteristics & thus efficiency of the engine. Study of wear phenomenon is very challenging particularly for the gaskets because of nonlinear behavior of geometries, material nonlinearities and in addition, the gaskets are made up of numerous layers with negligible thickness, which makes it further challenging. The wear in Automobile Engine components and particularly in gaskets is an area, which has not been studied extensively. This paper majorly focuses on a computational approach to capturing the wear phenomenon on the gaskets. One of the most critical hot end durability tests of the engine was replicated in a simulation environment by considering all the relevant physics from the physical test. To simulate wear phenomenon, the classical Archard’s wear model was implemented in a UMESHMMOTION Fortran subroutine code and solved in the Finite Element Software ABAQUS/Standard. To consider the removal of material and geometry change due to wear, the Arbitrary Lagrangian-Eulerian meshing technique of ABAQUS was used.

Reddy, Rajavardhan, R B, Govind, Kulkarni, Sanjeev, Palve, Chandrakant, Mueller, Frank Oliver

Exploring the Effects of Oil Cooler Deletion on Tractor Engine Operation

2026-26-0547

1/16/2026

An optimal engine lubrication system, encompassing engine oil and an oil cooler, is critical for thermal management and minimizing frictional losses. This system ensures adequate lubrication and cooling of engine components, thereby maintaining optimal performance. This study investigates the implications of oil cooler removal in a 45HP inline engine tractor. Various validation trials were conducted, including high ambient temperature tests under worst-case conditions, high coolant temperature scenarios, and a rigorous tractor killer test. In the latter, the tractor underwent 100 hours of operation on a PTO bench at maximum engine RPMs. Despite an observable increase in lubricant oil temperature during these tests, the tractor did not exhibit any component seizure or failure. The findings aim to determine whether the inclusion of an oil cooler is essential for the engine's operational reliability. This research offers valuable guidance for optimizing hardware selection and cost- effective design strategies in off-highway vehicles. Cost reduction remains a significant challenge for engine manufacturers, particularly for off-highway application vehicles, as they strive to ensure robust performance without compromising reliability.

Gupta, Deepak, Kumar, Pankaj, Singh, Manjinder, Singh, Gagandeep, Kumar, Munish, Singh, Harpreet, Singh, Maninder

Engine Oil Fluctuation Study in HLA Gallery and Impact of VVT Cam Phasing on Oil Fluctuation

2026-26-0559

1/16/2026

Oil pressure, the most fundamental to engine's performance and longevity, is not only critical to ensure that the engine components are properly lubricated, cooled, and protected against wear and contamination, but also ultimately contributing to reliable engine performance. Due to several factors of engine such as, rotational fluctuation, aeration, functioning of hydraulic components there are fluctuations in oil pressure. In engines, with a crank-mounted fixed displacement oil pump (FDOP), these inherited pressure fluctuations cannot be eliminated completely. However, it is very necessary to control the abnormal oil pressure fluctuation because abnormal pressure fluctuation may lead to malfunction of hydraulic component functioning like variable valve timing (VVT), hydraulic lash adjuster (HLA) and dynamic chain tensioner which can further cause serious issues like excessive or sudden load drops, unstable engine performance, valve train noise, improper valve lift operation etc. In this paper, engine oil pressure fluctuation in HLA gallery is studied, and its impact was assessed on valve train system. Root cause analysis (RCA) was conducted using high frequency oil pressure measurement to understand the various reasons impacting high oil pressure fluctuations inside HLA galleries. Time domain analysis was performed to understand oil pressure fluctuations with respect to VVT cam phasing. Angle domain analysis was performed to assess the impact of oil pressure fluctuations on valve train behavior. Further findings from this study aim to enhance the understanding of impact of VVT cam phasing in oil pressure fluctuations.

Kumar, Ashok, Choubisa, Manas, Kumar, Ravi, Pathak, Mehul

Engine Compartment Front End Module & Snorkel Placements to Achieve Maximum Volumetric Efficiency

2026-26-0588

1/16/2026

The rising demand for electric vehicles (EVs) has pushed automakers to prioritize visual brand consistency across both EVs and internal combustion engine (ICE) vehicles. A main design factor which is influenced by this trend is the front grille. In order to achieve uniform aesthetic looks, passenger car manufacturers often reduce the front grille openings and limit airflow. This closed grille style is common in electric vehicle. However, this creates challenges for internal combustion engine (ICE) vehicles with snorkel-type air intake systems, leading to reduced airflow and higher temperatures in the engine bay and intake air which eventually gets sucked in the engine resulting in low volumetric efficiency. Maintaining a cooler intake air is vital for ICE performance. Adjusting snorkel position and airflow patterns in low temperature zones ensures the engine receives air at low temperatures. This improves the combustion efficiency, throttle response and eventually it reduces the risk of knock. This study emphasizes the need to control intake air temperature in such a way that the air intake system supports to meet performance and emissions targets. In our study, we use simulation tools such as computation fluid dynamics (CFD) and experiments in order to demonstrate that the ICE vehicle grille design having restricted air flow which are similar to the electric vehicles, increases the air temperature that enters into the snorkel of air intake system. This pre-heated air that enters into engine reduces its efficiency, power output and also might eventually affect the emissions. The findings in our study quantifies the thermal penalty that are linked to this design standardization. In order to overcome these issues, the study recommends tailored front-end module thermal management strategies for ICE vehicles particularly for air intake system. The approach optimizes airflow and minimizes heat gain in snorkel of air intakes and hence preserving engine performance without sacrificing the visual consistency between EV and ICE models.

Sonone, Sagar Dinesh, Singh, Nil Kanth, Kolhe, Vivek M, Kulkarni, Chaitanya, Malekar, Hemant A

Optimizing Diesel Engine Performance through Parametric Study of Fuel Injector Configurations for Enhanced Sustainability

2026-26-0402

1/16/2026

The pursuit of sustainable transportation solutions requires continuous improvement in engine efficiency and performance. This study presents a comprehensive parametric analysis of high-horsepower diesel engine combustion modeling, focusing on fuel injector configurations to optimize power density and overall engine efficiency. The model was first validated with experimental data. Based on the validated model, a series of Design of Experiments (DoE) simulations were conducted, examining four distinct fuel injector hole configurations, each with four different spray inclusion angle (umbrella angle) variations. The set of different fuel injector configurations was selected through benchmarking analysis. The primary objective was to identify the most effective injector design for improved combustion characteristics and engine performance. Upon determining the superior configuration, further simulations were performed with increased injector through – flow to fine-tune the optimal design. Additionally, the piston bowl configurations were adjusted to achieve better combustion efficiency. The methodology involved advanced computational fluid dynamics (CFD) modeling techniques to simulate various injector configurations under diverse operating conditions. Performance metrics such as power rating, fuel-specific consumption, combustion efficiency, and emissions were meticulously analyzed to evaluate each configuration's impact on engine power density and overall efficiency. Results revealed noticeable variations in engine characteristics across different injector designs. The optimal configuration demonstrated superior fuel atomization and spray characteristics, enhancing combustion efficiency and reducing emissions, and the results were also correlated with the experimental findings. These findings provide valuable insights for the development of more sustainable and efficient high-horsepower diesel engines.

Ailaboina, Akhil, Gandhi, Naresh, Marwaha, Akshey, G, Suwarna, Chogule, Vijay, Bhat, Vishal

Improving Late Pilot Injection Strategy in Dual-Fuel Diesel/Methane Engines through Supercharging and Hydrogen Enrichment

03-18-08-0049

12/24/2025

In this study, a novel dual-fuel combustion strategy is investigated, employing late pilot injection in diesel–methane engines to improve performance and reduce emissions. The engine was first tested with conventional diesel and methane, exploring a wide range of pilot injection timings, injection pressures, and intake boost pressures. Subsequently, experiments were repeated using a methane/hydrogen blend to assess the influence of hydrogen addition. Results show that, when using only methane, delayed pilot injections have minimal effects on engine performance. In naturally aspirated operation, unburned hydrocarbons and carbon monoxide are reduced, while in supercharged conditions, emissions increase; however, they remain within acceptable limits. Nitrogen oxides and particulate matter reach their lowest levels with delayed injection. Introducing hydrogen reduces engine performance and hydrocarbons and carbon monoxide emissions; notably, it suppresses the typical nitrogen oxides increase associated with hydrogen, while also lowering particulate matter. These findings demonstrate that combining late pilot injections with hydrogen addition and supercharging is a promising strategy for improving dual-fuel engine efficiency and emissions, offering a potential pathway toward cleaner combustion.

Carlucci, Antonio Paolo, Strafella, Luciano, Ficarella, Antonio

The Technological Concept of a Self-Adjusting Segmented Ceramic Sealing System for a Turboshaft Engine with Isochoric Combustion

03-18-08-0046

12/8/2025

The article presents self-adjusting segmented ceramic seals designed for a novel turboshaft engine operating according to the Humphrey thermodynamic cycle. The sealing system is an integral part of the developed engine concept, which features rotating isochoric combustion chambers. The seals utilize centrifugal force as the sealing force, enabling uniform sealing regardless of thermal conditions and associated deformations. The sealing consists of segments with adjustable dimensions in both circumferential and transverse directions. The sealing elements should be made of Si3N4 ceramic, characterized by high thermal resistance (1300°C) and low thermal expansion (3.2•10−6/°C). The article presents three different variants of sealing systems, differing in terms of the technological possibilities of their manufacturing. Special treatments must be applied to ensure high machining accuracy of the sealing elements. The proposed sealing system is a critical point in the design of an engine with isochoric combustion chambers. Successful sealing is key to the implementation of the Humphreys thermodynamic cycle, which offers higher engine efficiency compared to classical turboshaft engines available on the market. The article concludes with the presentation of a model for experimental investigations, along with its thermal analysis.

Tarnawski, Piotr

A Review of the Application and Research Progress of Turbulent Jet Ignition Technology

03-18-08-0047

12/3/2025

For the sustainable development of human society, energy saving, emission reduction, and carbon reduction are urgent challenges to be addressed in the energy industry. As a power device for energy conversion in the transportation sector, the internal combustion engine also needs to enhance its thermal efficiency while cutting pollutant emissions. To meet the current stringent requirements, lean combustion has been widely studied as an effective strategy. However, the ignition difficulty resulting from lean burn needs to be addressed. As a high-energy ignition system, the prechamber turbulent jet ignition can accelerate in-cylinder combustion, thereby enhancing engine efficiency and reducing emissions. Thus, it is considered a promising technology. This review reveals efforts to apply prechamber ignition systems to optimize combustion in the engine characterized by low-carbon fuels and low-emission features. First, this article briefly introduces the evolution of the prechamber turbulent jet ignition technology. Second, the ignition mechanism, the influence of fuel in the prechamber and structure of prechamber on the combustion performance of the spark ignition engine are emphatically introduced. The structural parameters like nozzle diameter, nozzle orientation, nozzle number, and prechamber volume have a significant effect on the in-cylinder combustion. This review summarizes the research achievements regarding the structural parameters. Finally, this study demonstrates the performance improvement of engines equipped with turbulent jet ignition technology.

Bai, Xiujuan, Zheng, Dayuan

Feasibility of Ammonia as a Spark-Ignition Engine Fuel: Strategies for Combustion Stability and Engine Efficiency

2025-01-0531

11/25/2025

Ammonia (NH3) is a promising energy carrier and a potentially alternative fuel to selected sectors due to its carbon-free nature and its relatively high energy density. However, its low reactivity and slow flame propagation pose significant challenges for a direct use in an internal combustion engine, and stable operation at all engine’s conditions. This study investigates three combustion strategies for utilizing NH3 in an adapted four-cylinder 2 L turbocharged, compression-ignition engine, adapted for spark-ignition (SI) operation. Initially, the engine was tested using pure ammonia as fuel, obtaining high efficiencies and acceptable stability at medium/high loads. Nevertheless, intense combustion instabilities could not be avoided below a minimum load level (which increases with engine speed), making engine operation unfeasible in approximately 30 % of its operating map. To address these limitations, two enhancement strategies are explored: Firstly, hydrogen (H2) doping pre-mixed with NH3 to enhance the fuel properties and secondly the implementation of a passive turbulent jet ignition (TJI) system, with a target to accelerate flame propagation. H2 on-board supply and storage is not part of this study and H2 could be generated through a downsized NH3 reformer of the types being currently developed for maritime and power generator applications. Experimental results indicate that the addition of small amounts of H2 (2 to 4 % in mass) significantly improves both combustion stability and thermal efficiency due to increased flame speed. These findings highlight the feasibility of NH3 as a fuel for spark-ignited engines, provided that suitable combustion enhancement techniques are implemented.

Karageorgiou, Dimitrios, Myslivecek, Matej, Gaillard, Patrick, Gomez-Soriano, Josep, González-Domínguez, David, Lujan, Jose, Alcarria Laserna, Gerardo

Ammonia Combustion with Active Pre-Chamber Spark Plug - a CO ₂ -Free Combustion Process

2025-01-0527

11/25/2025

As a zero-carbon fuel, ammonia has the potential to completely defossilize combustion engines. Due to the inert nitrogen present in the molecule, ammonia is difficult to ignite or burn. Even if the ammonia can be successfully ignited, combustion will be very slow and there is a risk of flame quenching, i.e. the flame going out before the ammonia-air mixture has been almost completely converted. Both the difficult flammability and the slow combustion result in high ammonia slip, which should be avoided at all costs. The engine efficiency is also greatly reduced. Safe ignition and burn-through can be achieved by drastically increasing the ignition energy and/or using a reaction accelerator such as hydrogen. The planned paper will use detailed 1D and 3D CFD calculations to show how high the potential of ammonia combustion in an internal combustion engine is when an active pre-chamber is used as the ignition system. As a result of the flame jets penetrating into the main combustion chamber filled with ammonia, this allows a so-called space ignition and a very high ignition energy to be achieved. The latter is particularly high if the fuel used in the pre-chamber is hydrogen, for example. As hydrogen can be obtained directly from the ammonia via an on-board cracker in the vehicle, this would be a single-fuel combustion process. The paper will focus on the potential how fast and save the combustion can be, what combustion efficiencies can be obtained and what amount of hydrogen is needed from the onboard cracker (operated with Waste heat from the exhaust system) to build a very stable and highly efficient ammonia-based passenger car combustion system.

Sens, Marc, von Roemer, Lorenz, Rieß, Michael, Fandakov, Alexander, Casal Kulzer, Andre

In-Flight Evaluation of Sustainable Hydrocarbon Fuels in Compression Ignition Aircraft Engines

2025-01-0533

11/25/2025

As global air traffic is expected to increase significantly in the coming decades, reducing the associated climate impact requires scalable solutions. While alternative propulsion technologies such as electric and hybrid-electric systems might offer long-term potential, their current applicability remains limited due to low energy density, limited range and scalability, and system complexity. Consequently, thermodynamic propulsion systems – such as gas turbines and piston engines – are expected to remain dominant in the medium term. In this context, sustainable hydrocarbon-based aviation fuels represent a practical and necessary solution. Certified sustainable aviation fuel (SAF) pathways are currently approved exclusively for use in gas turbines, with certification standards tailored to turbine-specific requirements. Consequently, fuel properties such as cetane number and evaporation behavior are not included in existing specifications. However, when SAF-kerosene blends are used in compression ignition engines, the impact of these properties on ignition quality, combustion behavior, and emissions must be specifically evaluated. For this purpose, a flight test campaign was conducted using a fully instrumented Diamond DA42 aircraft, configured as a flying laboratory and equipped with serial-production piston engines. Two synthetic fuel variants were evaluated: one certified according to ASTM D7566-23a Annex A2 (HEFA SPK) and a second, Tall Oil derived fuel with a distinctly different molecular composition – characterized by an increased content of cycloparaffins and low aromatics content. The aircraft as a flying air lab was equipped with special engine measurement technology including high-pressure in-cylinder indication to analyze the impact of these differing fuel compositions on engine efficiency and combustion characteristics, including ignition delay and peak pressure. Furthermore, a mobile emission and particle number measurement system enabled the assessment of environmental performance under real flight conditions. Both fuels demonstrated significant reductions in thermal NOx formation due to their low aromatics content. However, no clear benefit was observed in total particle number (PN), likely due to a shift in the particle size distribution towards the nanoparticle regime.

Kleissner, Florian, Hofmann, Peter, Vogd, Philipp, Vauhkonen, Ville, Käkölä, Jaana, Greve, Alina

Cooling System Design Approach for Off-Road Vehicles Using 3D CFD and 1D Tools

2025-28-0260

11/6/2025

The average product development cycle spans 3-5 years, involving extensive virtual and physical testing of the machine. Advances in simulation tools have significantly enhanced our ability to identify product solutions early in the design phase. Tools like 1D KULI and Creo Flow Analysis (CFA) offer faster solutions in less time, thereby accelerating the product development cycle. Cooling systems are crucial components of off-highway tractor machines, directly affecting engine efficiency and overall machine functionality. An optimized cooling system ensures the engine operates within safe temperature ranges, preventing overheating and potential damage. Thus, designing an effective cooling system is a vital aspect of machine engineering. 3D Computational Fluid Dynamics (CFD) simulations are essential for evaluating cooling system performance. These high-fidelity simulations provide detailed insights into fluid flow and heat transfer, enabling engineers to predict and enhance cooling efficiency. However, 3D CFD simulations require significant manual effort for preprocessing and postprocessing, as well as substantial computational resources, making them time-consuming and costly. Low-fidelity solvers, such as 1D KULI analysis and Creo Flow, offer practical alternatives for analyzing cooling systems in the early design phase. These tools can correlate well with predictions from traditional 3D CFD software, providing accurate results with reduced computational effort. By transitioning from 3D to lite 3D and 1D simulations, engineers can save considerable time and money on preprocessing, postprocessing, and high-performance computing (HPC) costs. This paper focuses on the correlation practices between traditional 3D software and low-fidelity solvers, highlighting various methods that impact the lead time for product development.

Ukey, Snehal, Tirumala, Bhaskar, Nukala, Ramakrishna

Effective Power Management on Diesel Engine Using Electrified Turbocharger

2025-28-0242

11/6/2025

The growing demand for improved fuel efficiency and reduced emissions in diesel engines has led to significant advancements in power management technologies. This paper presents a dual-mode functional strategy that integrates electrified turbochargers to enhance engine performance, provide boost and generate electrical power. This helps in optimizing the overall engine efficiency. The engine performance is enhanced with boosting mode where the electric motor accelerates the turbocharger independent of exhaust flow, effectively reducing turbo lag and provides immediate boost at low engine speeds. This feature also improves high altitude performance of the engine. Conversely, in generating mode, the electric turbocharger recovers or harvest energy from exhaust gases depending on engine operating conditions, converting it into electrical energy for battery recharging purpose. Advanced control systems enable real-time adjustments to boost pressure and airflow in response to dynamic driving conditions, maximizing engine efficiency. Simulation studies and engine testing validate the expected benefits, demonstrating that the electrified turbocharger can significantly facilitate engine downsizing, reduce fuel consumption, and lower emissions through precise power management. These advancements align with global sustainability goals, presenting a viable solution to meet stringent environmental regulations while maintaining robust engine performance. The integration of electrified turbochargers represents a critical step towards the next generation of eco-friendly diesel engines, supporting both environmental sustainability and economic efficiency.

Borle, Shraddha, Prasad, Lakshmi, Couvret, Sebastien, Fournier, Hugo, Chenuet, Laurent

Computational Fluid Dynamics (CFD) Analysis of Turbocharger Aerodynamics and Thermal Behaviour in Automotive Applications

2025-28-0229

11/6/2025

Turbocharging is a vital technology for enhancing internal combustion engine (ICE) performance and efficiency while enabling engine downsizing to reduce fuel consumption and emissions. This research analyzes turbocharger systems by examining their components—turbine, compressor, intercooler, and waste-gate—and their roles in boosting engine efficiency. It explores how exhaust energy drives the turbine to compress intake air, improving power output. The study evaluates turbocharger impact on fuel economy, emissions, and engine response under various driving conditions. It also considers wheel design, material selection, and durability under high temperatures and speeds. Advanced simulations using CFD and FEA analyze airflow, pressure, and thermal behavior to optimize performance. This research affirms turbocharging’s role in creating high-performance, fuel-efficient, and environmentally sustainable engines, offering insights that support the design of next-generation automotive propulsion systems with improved thermal management and emissions control.

Chandrashekar, B. Aditya, Bhaduria, Abhishek

Performance Analysis of a Hydrogen-blended Naturally Aspirated Gas Engine with a Dedicated Exhaust Gas Recirculation System

2025-32-0046

11/3/2025

With the publication of the Renewable Energy Directive (RED) III in 2022, the European Union increased its renewable energy consumption target to 42.5% by 2030. Consequently, gaseous fuels derived from renewable electricity, particularly green hydrogen, are expected to play a pivotal role in the decarbonization of the energy sector. One promising application of green hydrogen is its integration into combined heat and power (CHP) plants, where it can replace natural gas to reduce CO2 emissions. Pure hydrogen as fuel or blended with natural gas has demonstrated potential for lowering both pollutant emissions and fuel consumption while maintaining or even enhancing engine performance. But it is expected, that the amount of available green hydrogen will be limited in the beginning. So new engine systems with hydrogen and natural gas for CHP plants are required, that offer more CO2-benefit and NOx reductioon than from fuel substitution only. In the LeanStoicH2 project, a novel approach was developed to optimize the operation of a four-cylinder stationary gas engine for hydrogen utilization. The project introduced a customized exhaust gas recirculation (EGR) system in which the exhaust gas from a hydrogen-fueled cylinder is fully recirculated into the intake mixture of three other cylinders operating stoichiometrically with natural gas. This configuration leverages the benefits of both lean and stoichiometric combustion strategies. After passing a lower temperature condenser, the dry recirculated exhaust gas, which is CO2- and H2O-free, dilutes the intake mixture of the three cylinders, mimicking lean operation and thus increasing engine efficiency due to the higher isentropic coefficient (κ). Simultaneously, this approach reduces combustion temperatures, thereby lowering knock tendency and engine wear. Furthermore, the stoichiometric operation of the EGR-receiving and emission relevant cylinders allows for the effective use of a three-way catalyst, significantly reducing pollutant emissions. Experimental results confirm that this innovative combustion strategy enhances indicated efficiency from 41.5% to 43.5% compared to series operation, and maintains low NOx tail pipe emissions. These findings highlight the potential of advanced hydrogen combustion strategies to improve the sustainability and performance of gas engine CHP plants, supporting the transition toward a greener energy landscape.

Salim, Naqib, Beltaifa, Youssef, Kettner, Maurice

Model-Based Design and Numerical Analysis of a Downsized Centrifugal Pump for Engine Cooling Applications

2025-32-0078

11/3/2025

The water pump is the crucial component of the engine cooling system. It is usually designed considering as rated conditions the ones evaluated when the engine delivers its maximum power. This results in an overdesign of the pump, considering that almost never the engine delivers the maximum power, in usual operation. At these conditions, in fact, flow rate and pressure delivered reach the maximum values, which are not needed to cool the engine in most probable operating conditions. In fact, considering the real operating conditions during a typical driving mission or a homologation cycle, the mechanical power is far away from the maximum datum, as well as the cooling flow rate and pressure delivered by the pump. To a so unbalanced design for the pump corresponds a low efficiency of it, being the technology oriented to use a centrifugal type, whose efficiency is quite dependent on speed of revolution and flow rate delivered. Hence, modifying the design point of the pump causes a mechanical energy saving, improving the organic efficiency and reducing the efficiency penalization when it operates, as it happens always, at off design conditions. In this work, a model-based procedure to design a centrifugal pump in a more suitable engine working point from the point of view of the energy absorbed is considered. The procedure starts with an estimation of the engine thermal needs in different working conditions and on a driving cycle. Hence, a flow rate is targeted, and a pressure drop of the cooling circuit estimated, to have the specifics of the pump design. The model is able to evaluate all the hydraulic losses of the pump in its impeller and volute. The geometry generated has been refined and finally investigated through numerical CFD analysis. Subsequently, the turbulent flow field of the pump was analyzed in terms of static pressure, velocity, and kinetic energy distribution. The pump head and flow rate delivered were simulated using CFD techniques and compared with experimental results, assessing also the efficiency of the pump and the loss distribution. Finally, the pump performance has been evaluated along a driving cycle, to assess the energy absorbed during a real operating condition.

Di Battista, Davide, Deriszadeh, Ali, Di Prospero, Federico, Di Giovine, Giammarco, Di Bartolomeo, Marco, Fatigati, Fabio, Cipollone, Roberto

Reactivity Retention of Modern Converters for Stringent Emission Control

2025-01-0401

10/7/2025

The growing emphasis on environmental protection and sustainability has resulted in increasingly stringent emission regulations for automotive manufacturers, as demonstrated by the upcoming EURO 7 and 2027 EPA standards. Significant advancements in cleaner combustion and effective aftertreatment strategies have been made in recent decades to increase the engine efficiency while abiding by the emission limits. Among the exhaust aftertreatment strategies, three-way catalyst has remained the primary solution for stoichiometric burn engines due to its high conversion efficiency and ability to simultaneously allow both oxidative and reductive reactions in a single stage with spatial separation due to the oxygen storage capabilities of ceria. However, fuel and lubricant-borne sulfur and phosphorus compounds have been shown to have a significant long-term effect on the activity of three-way catalysts, particularly during the lean-rich transitions and oxygen storage processes. In the present study, the impact of sulfur contamination on the conversion efficiency and oxygen storage capacity of the three-way catalyst has been investigated on a heated flow reactor bench platform. The influence of sulfur accumulation on the water-gas shift reaction and activity of ceria has been studied. Additionally, the process of sulfur removal at high temperature (~700-750°C) has also been explored. Relevant engine-out exhaust conditions from the SI engine platform, including flow, temperature, and exhaust species (individually), were replicated on a heated aftertreatment flow bench during contamination and regeneration cycles. A comprehensive analysis of species before and after the catalyst sections was performed using Fourier-transformed infrared (FTIR) and mass spectrometers to study and quantify the conversion and formation of species including sulfur species (sulfur dioxide and hydrogen sulfide) and hydrogen, under different catalyst conditions. The conversion selectivity of sulfur species during regeneration is also investigated. The results show that sulfur contamination causes a substantial reduction in oxygen storage capacity. Effective sulfur removal required a combination of high temperature (~700°C or higher) and lean-rich cycling; absence of either condition resulted in incomplete desulfation and the selectivity towards sulfur dioxide and hydrogen sulfide was largely dependent on the reductant species used during high temperature desulfation.

Sandhu, Navjot Singh, Yu, Xiao, Jiang, Chuankai, Ting, David, Zheng, Ming

Advanced Plasma-Based Ignition Strategy for Future Spark Ignition Engines

2025-24-0020

9/7/2025

Internal combustion engines will continue to play an important role in transportation for decades to come because of the high onboard energy density. For present passenger vehicles, efforts have been made to reduce the cold start emissions and improve engine efficiency. To reach such goals, lean and diluted mixtures are needed to reduce the chemical reactivity of the mixture, so a higher engine compression ratio can improve thermal efficiency. The decreased flame temperature of the lean/diluted mixtures is also beneficial for NOx reduction. Strong in-cylinder flow is needed to increase flame propagation speed for efficient and complete combustion process. Strong ignition sources are needed to provide robust ignition to support the combustion process. In this paper, the application of advanced plasma-based ignition strategies was reviewed, with special attention to the on-demand plasma energy profiling, which has flexible control over discharge duration and current amplitudes. The ignition performance of multi-core ignition is compared with on-demand energy profiling under cold start and engine idling conditions. For heavy-duty applications burning low and zero carbon renewable fuels with less chemical reactivity, such as ammonia and natural gas, a novel ignition source with remote chamber and detonation tube is also demonstrated for the first time. The air-fuel mixture in the remote ignition chamber can be ignited, and the flame front can propagate and accelerate along the detonation tube to detonation stage, known as the deflagration-to-detonation transition. The high-speed detonation wave has a much stronger ignition capability to improve combustion efficiency of mixture with low chemical reactivities.

Yu, Xiao, Leblanc, Simon, Reader, Graham, Zheng, Ming

Toward Sustainable Heavy-Duty Transport: Evaluating Charge Dilution and Advanced Corona Ignition System Effects on SI Natural Gas Engine Efficiency and Combustion Characteristics

2025-24-0024

9/7/2025

Reducing greenhouse gas (GHG) emissions in the transportation sector is a significant challenge. A multi-technology approach is the most practical and sustainable solution for minimizing the environmental impact of road transport. Alternative gaseous fuels derivable from bio sources have the potential to significantly cut equivalent carbon dioxide (CO2eq) emissions from a Well-to-Wheel (WtW) perspective, and the development of technologies that allow to improve the efficiency of natural gas-powered Heavy Duty (HD) Spark Ignition (SI) engines is of strategic importance. In such applications, charge dilution strategies might have the potential to increase engine efficiency at a relatively low implementation cost. Diluting the in-cylinder charge can reduce fuel consumption by decreasing wall and pumping losses, and increasing the Heat Capacity Ratio (γ). The coupling with innovative technologies aimed at enhancing ignition energy, influencing combustion development, could be a promising scientific path for achieving more significant results. This work presents an experimental study conducted on a modern natural gas HD SI Single Cylinder Engine (SCE) to analyze the efficiency and emission benefits achievable through charge dilution. Additionally, a characterization of the prototypal 2nd generation Advanced Corona Ignition System (ACIS gen2) was conducted for a preliminary assessment of its potential in gaseous fuel context, and to investigate the effects of its higher ignition energy on combustion features under both diluted and non-diluted charge conditions. The steady-state tests have been carried out across the low/medium load and speed range of the engine map, replicating the most common operating conditions for on-road use cases. The results highlight that charge dilution positively impacts the thermodynamic efficiency of gas HD SI engines within specific limits, lowering the Indicated Specific Fuel Consumption (ISFC) by up to 10%. The ACIS gen2 reduced the combustion duration, particularly impacting the early stages, producing an additional improvement in the ISFC of 1% to 2% in stoichiometric conditions; and suggested further potential that could be obtained by optimizing the entire system. Both technologies show that their use could be beneficial in hydrogen applications.

Di Domenico, Davide, Napolitano, Pierpaolo, Papi, Stefano, Ricci, Federico, Golini, Stefano, Rapetto, Nicola, Giordana, Sergio, Beatrice, Carlo

Combustion System Optimization of Commercial Vehicle Hydrogen Engines via 3DCFD Simulations and Single Cylinder Engine Measurements: Injector Cap, Injection Strategy and Intake Duct Design

2025-24-0008

9/7/2025

The development of hydrogen fueled engines has dramatically accelerated in recent years. They have gained much in operating reliability and the specific power outputs is at least comparable to those of current natural gas engines. This has been made possible by combining specific development tools derived from the development of compression-ignition and spark-ignition engines. These include jet visualization techniques (Schlieren, PIV, and LIF), video endoscopy on engine, and 3-D fluid dynamics simulations. In hydrogen engines for commercial vehicles, efforts have so far been made to keep engine components as unchanged as possible from similar diesel or gasoline versions. Similarly, some manufacturers have favored the port fueled injection (PFI) solution because it is easier to implement than the in-cylinder (DI) injection one. The present work concerns the evaluation of the further improvement potential made possible by using direct injection (DI) technology, and intervening on both the geometry of the intake ducts and the design of the injector-mounted cap. The analysis of these interventions makes use of single-cylinder engine measurements and 3D CFD calculation of the fuel mixing process during the compression phase. Moreover, the flexibility of the direct injection system, that allows changing the injection timing with further improvement on the engine efficiency, was also considered. Despite the maturity already achieved by the hydrogen engine for commercial vehicle applications, the measurements and the simulations outlined in the present work throws new light in the further (high) development potential of this technology.

Gaballo, Maria Rosaria, Iacobazzi, Marino, Burtsche, Thomas, Cornetti, Giovanni

Waste Heat Recovery in Hydrogen Fueled Internal Combustion Engines

2025-24-0108

9/7/2025

Waste Heat Recovery is one of the most investigated and promising technologies for energy efficiency in the transportation sector. It consents to maintain the high-level technology of the present propulsion systems, based on Internal Combustion Engines, while increasing the overall engine and vehicle system efficiency. At the same time, the use of alternative fuels, like hydrogen, has the same crucial role to reduce harmful and greenhouse emissions, without overturn the existing mature technology. A hydrogen-fueled Internal Combustion Engine is proposed in this paper, equipped with waste heat recovery consisting in an additional radial turbine downstream the turbocharger of the engine (Turbo-Compound). The aim is to have a reduction of the specific consumption in most of the operating points of the engine, considering the effect of the recovery and the engine equilibrium rearrangement. The use of hydrogen increases recoverable enthalpy at the engine exhaust, which is intended to be recovered through an expansion of the gases inside the additional turbine. When this secondary turbine is installed downstream of the turbocharger, the overall engine backpressure increases. This alters the turbocharger's operating point, which in turn shifts the engine’s operating conditions. Ultimately, this has a counterproductive effect on the engine efficiency: it faces higher backpressure at exhaust valve opening, leading to an increase in specific fuel consumption. This paper examines the modifications to the engine’s exhaust line resulting from the conversion of waste heat into mechanical energy via a Turbo-Compound system. It discusses the conditions under which the system yields a net positive effect, primarily by compensating for the increased back pressure it introduces. Changes in key engine parameters—such as Variable Geometry Turbocharger control, boost pressure, air/fuel mass flow rate, and equivalence ratio—are analyzed, along with their influence on in-cylinder pressure. Furthermore, the paper identifies the operating range in which the Turbo-Compound system provides a net performance benefit.

Di Battista, Davide, Cipollone, Roberto, Corti, Enrico, Brancaleoni, Pier Paolo, Di Prospero, Federico, Ravaglioli, Vittorio

Analysis of Combustion Characteristics and Performance of a Multi-Cylinder Engine Operating on Syngas/Diesel in Dual-Fuel Mode

2025-24-0042

9/7/2025

Despite improvements in internal combustion engine efficiency, fossil fuel reliance remains a challenge for sustainable energy. Syngas, a hydrogen-carbon monoxide mixture produced from gasification, typically of carbon-based feedstocks, offers a viable transitional fuel due to its compatibility with existing combustion technologies and reduced emissions. However, its low ignition propensity elevated intake temperatures or pressures, a limitation that can be overcome through diesel pilot injection in dual-fuel engine configurations. This study extends prior single-cylinder research to a 1.6 L four-cylinder HCCI engine operating in dual-fuel mode, resembling a Reactivity Controlled Compression Ignition (RCCI) engine. The analysis focuses on cylinder-to-cylinder combustion variation, thermal efficiency, and pollutant emissions, with particular emphasis on the influence of diesel pilot injection timing. Experimental evaluations are conducted across a range of injection timing and Syngas flow rates (100 to 160 L/min). Key metrics include ignition delay, heat release rate, maximum pressure rise rate, coefficient of variation of indicated mean effective pressure, and pollutant emissions. Results indicate that diesel pilot injection timing significantly affects combustion phasing, heat release dynamics, and overall engine efficiency. Advancing or retarding the injection timing alters ignition delay and heat release characteristics, with optimal settings improving Syngas utilization and reducing particulate emissions. These findings highlight the importance of injection strategy optimization for realizing the full potential of Syngas in multi-cylinder engines, supporting their integration into cleaner and more efficient propulsion systems.

El Younsi, Laila, Nelson-Gruel, Dominique

Numerical and Experimental Investigation of a Pre-Chamber Igniter for Enhanced Low Load Stability in Internal Combustion Engines

2025-24-0002

9/7/2025

Developing innovative ignition technologies offers a crucial opportunity to improve the performance of internal combustion engines while significantly reducing harmful emissions, contributing to a more sustainable future. The replacement of the standard spark plug with a pre-chamber igniter is a well-known combustion accelerator for externally ignited engines for passenger vehicles. An increase in engine efficiency, especially at high loads, can be realized. However, pre-chamber ignition technology has not yet been widely adopted in the market, primarily due to the difficulty of achieving stable operation at lower engine loads. A better understanding of the flow and mixture conditions is needed to improve the combustion stability with the pre-chamber igniter in low-load operating conditions. The gas exchange in the passive pre-chamber was studied using a combination of numerical modelling and experimental methods. Accessing those parameters experimentally requires a high effort in test bench design and operation. To overcome the requirement for such elaborate test bench designs, robust and accurate numerical models, which are validated with available experimental data, should be used. A modelling approach was developed based on measurement data from a single-cylinder engine over a wide range of engine loads and injection timings, where it was employed to predict the flow and mixture characteristics inside the pre-chamber volume. The physical phenomena that dictate the operation limits measured in the experimental campaign can be identified through the numerical results, removing the limitations of experimental measurement. Furthermore, this study delves into the variation of the intake valve actuation and its effects on the pre-chamber gas exchange and combustion process under low engine load

Fellner, Felix, Härtl, Martin, Jaensch, Malte, D'Elia, Matteo, Burgo Beiro, Marcos, Nambully, Suresh Kumar, Rothbauer, Rainer

CFD-Driven Optimization of Diesel Injection for a Hydrogen-Diesel Dual Fuel Engine

2025-24-0045

9/7/2025

Among the alternatives to the use of fossil diesel fuel, dual fuel combustion, leveraging hydrogen as the low-reactivity fuel, represents a promising approach for both reducing pollutant emissions and improving brake thermal efficiency. In addition, this innovative combustion mode requires minimal modifications to the existing Diesel engines architecture. This study was conducted on a Diesel engine (naturally aspirated, 3-cylinder, 1 L, direct injection), properly modified by the authors to operate in dual fuel mode with port fuel injection of hydrogen. A set of experimental data was used to calibrate the 1D and the 3D-CFD models for both Diesel and diesel-hydrogen dual fuel configurations. The AVL FIRE M 3D-CFD software was employed to model diesel injection and combustion, while the gas exchange process was analyzed by GT-Power. The validated 3D-CFD model was then leveraged to optimize the baseline diesel injection strategy in dual fuel mode, minimizing diesel consumption while maintaining stable combustion and comparable performance with respect to the baseline Diesel engine. Notably, the analysis highlights that, at low loads, where hydrogen energy fraction is limited, a diesel injection strategy consisting of two fuel pulses is required to ensure stable ignition. However, as the hydrogen contribution increases, the main injection can be reduced or eliminated, with the pilot injection alone being sufficient to ignite the premixed charge, without compromising engine efficiency. This optimized strategy enabled a simultaneous reduction in diesel usage, up to −62.6%, and a marked decrease in emissions, with the best reductions reaching −62.5% for CO₂, −81.1% for CO, and −31.6% for NOₓ.

Rinaldini, Carlo, Pisapia, Alfredo Maria, Scrignoli, Francesco, Volza, Antonello, Rossetti, Salvatore, Mancaruso, Ezio

SAE Truck & Off-Highway Engineering: August 2025

25TOFHP088/14/2025

A model of design efficiency How Cummins used modeling and other advanced design software to create its most efficient engines yet. Solving problems and seeking big ideas PACCAR's Phil Stephenson previews SAE COMVEC 2025 and offers insights into powertrain diversification, the role of AI, a software-defined future and the importance of people. Refurbishing high-voltage batteries for electric trucks Mercedes-Benz Trucks employs "like-new" reworked batteries to expand its spare parts portfolio and to inform future battery designs that are more sustainable. Editorial Hydrogen's humming in power generation Bosch invested in large-scale metal 3D printing Schaeffler optimizes rolling bearings for hydraulic and axle drives Natural gas infrastructure is scaling fast for HD fleets Cummins powers up the S17 genset SAE J3400/2 update brings quicker NACS charging Workhorse's W56 is the people's champ of electrified work vans Komatsu logs a new timber machine Product Briefs SPOTLIGHTS: Power Generation; Adhesives Q&A Volvo CE not letting up on electric

A MODEL OF DESIGN EFFICIENCY

25TOFHP08_01

8/1/2025

How Cummins used modeling and other advanced design software to create its most efficient engines yet. As AI and other deep-learning tools begin to help shape the transportation industry, they also bring improvements to existing technology. Modeling and simulation software has rapidly become a crucial tool for improving the design process of new diesel engines. More than two decades after the first X15 engines rolled off the assembly line, Cummins has applied today's modeling tools to help create the HELM version of the X15. The HELM architecture (which stands for Higher Efficiency, Lower emissions and Multiple fuels) is the company's basis for a global platform capable of meeting all manners of emissions regulations while still serving customers across a wide variety of use cases.

Wolfe, Matt

Comprehensive Analysis of Aero-Thermal Flow Characteristics in an Agricultural Tractor Using Computational Fluid Dynamics Simulation

05-19-02-0014

8/1/2025

This study employs computational fluid dynamics (CFD) to analyze airflow and thermal characteristics within an agricultural tractor, focusing on operator comfort and component safety. Initial simulations identified hotspots, such as the brake pedals, operator platform, and hand throttle, where temperatures exceeded acceptable limits (rise over ambient, ROA). A multi-step approach—including sealing air leaks, adding heat insulation materials, and optimizing the deflector guard—was implemented to mitigate excessive heat. While these modifications significantly improved temperature conditions on the right platform, the left brake pedal remained problematic. Further enhancements, such as sealing an electrical socket and modifying the shroud design, effectively reduced heat exposure. The improved shroud also led to a slight decrease in static pressure (2.21%) and an 8.61% reduction in power consumption, improving airflow efficiency. Although an alternative ring fan design reduced power consumption, it increased pressure, potentially restricting airflow. Conversely, sealing and shroud design modifications improved efficiency with a slight decrease in static pressure (2.21%) and a small increase in air velocity (1.5%). The findings demonstrate that strategic design modifications can enhance both operator comfort and engine efficiency. This study highlights the potential of CFD simulations as a powerful tool for optimizing agricultural vehicle thermal management.

Mohan, Anand, Soni, Peeyush, Sethuraman, Sriraman, Govindan, Senthilkumar, Sakthivel, Ananth, Babu, Rathish Maller

Effect of Water Dilution and Homogenous Lean Operation on Combustion and Detailed Emissions in a Spark Ignited Gasoline Direct Injection Engine

04-19-01-0004

7/10/2025

Twenty-nine percent of the greenhouse gas emissions in the US are produced by the transportation sector according to the US Environmental Protection Agency. The combination of increasingly stringent regulations on emissions and fuel economy, along with the current practical limitations of electrification motivate continued development efforts for improving internal combustion engine efficiency and emissions. Ethanol, an extensive fuel additive or drop-in replacement for gasoline, is already recognized as a promising transition fuel in decarbonization efforts. Furthermore, lean combustion in spark-ignited (SI) engines has been pursued extensively for engine efficiency and emissions improvements. Lean combustion, however, faces the challenges of decreased combustion stability and strong increases to engine-out NOx at conditions where conventional SI engines are stable (ϕ > 0.7). Water dilution, historically used as a knock inhibitor in performance engines, has shown potential for improving both emissions and efficiency in modern engines. This study evaluates the combined impact of homogeneous lean operation and water dilution on a 2.4L 4-cylinder naturally aspirated (NA) gasoline direct injection (GDI) engine fueled with a gasoline ethanol blend. The results indicate that efficiency during stable lean operation is maintained or improved, and NOx emissions are reduced by 15–40% depending on the level of water dilution. The lean stability limit is slightly degraded with water dilution; however, the decrease in NOx emissions allow for less lean operation while maintaining non-water-dilute efficiency improvement and emissions reduction. Detailed hydrocarbon emissions reveal that ethanol is nearly three times more sensitive to water dilution than gasoline, and hydrocarbon kinetic pathways associated with ethanol show a similar increased sensitivity to water dilution.

Voris, Alex, Lundberg, Matt, Puzinauskas, Paulius

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