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

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

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

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

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

2026-01-0327

4/7/2026

The discharge characteristics of ignition systems critically influence flame kernel formation and ignition stability under lean-burn conditions. This study experimentally compares a transistor coil ignition (TCI) and a capacitor discharge ignition (CDI) system in a constant-volume combustion chamber using hydrogen–air mixtures. The electrical behavior of both systems was first characterized through synchronized measurements of voltage, current, and high-speed imaging under various operating conditions with a resistive spark plug. The CDI system exhibited high-current (≈750 mA), short-duration (≈250 μs) discharges with strong instantaneous power but limited total spark-gap energy (≈5 mJ), while the TCI system produced lower-current, longer-duration (≈3 ms) discharges with higher cumulative energy (≈30 mJ). Flow-field tests revealed that the TCI discharge duration and energy release were strongly influenced by airflow, whereas CDI discharge behavior remained largely unchanged at flow

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

Accelerated Computed Tomography for Spray Characterization

2026-01-0341

4/7/2026

Computed tomography (CT) is a valuable diagnostic technique for visualizing spray plume direction and assessing mixture quality within combustion chambers under engine-relevant conditions. High-speed extinction imaging followed by tomographic reconstruction enables temporally and spatially resolved measurements of liquid volume fraction and plume evolution in multi-plume sprays. Traditionally, tomographic reconstruction requires capturing multiple angular views by rotating the injector and averaging over numerous injections to ensure statistical convergence. This process is time-intensive, particularly due to the large volume of data acquisition and the corresponding delays in data saving, particularly when acquiring many injections per view angle. In this study, we investigate the minimum number of injections required to achieve sufficient CT image quality, thereby significantly reducing experimental time. Two injectors are evaluated: a symmetric 8-hole Spray M injector from the

Yi, Junghwa, Wan, Kevin, Pickett, Lyle

Relative Knocking Intensity to Discuss Similarities and Differences between Low- and High-Speed Knocking Phenomena

2026-01-0312

4/7/2026

Knock intensity, the maximum half-amplitude of pressure oscillation, reaches 1 MPa once in thousands of cycles under a certain boosted high-load condition at the engine speed of 5000 min-1, which is named high-speed super knock. In the present study, a mass-production turbo-charged direct-injection gasoline engine is operated for the indicated mean effective pressure of 1.7 MPa at the engine speed of 1500 to 5000 min-1. Unburned-zone autoignition timing is estimated using Livengood-Wu integral coupled with a small set of ignition delay time equations, which matches that detected from the differential value of net heat release rate, with a difference below 2 degrees in the whole range of engine speed. As unburned-zone autoignition timing advances, ignition delay time in an unburned zone at the autoignition timing shortens. Whenever autoignition occurs at 15 degrees after TDC, the ignition delay time is the period of about 10 degrees, regardless of engine speed. Knock intensity divided

Zeng, Changzhi, Kuboyama, Tatsuya, Yatsufusa, Tomoaki, Okuyama, Shota, Kuwahara, Kazunari

Persistent Elevated Soot Emissions Induced by Clustered Stochastic Preignition Events

2026-01-0314

4/7/2026

Stochastic Preignition (SPI) is an abnormal combustion phenomenon that can occur in spark-ignition engines particularly under high-load operation. SPI is characterized by uncontrolled initiation of combustion prior to spark discharge, an abnormal combustion process that can lead to severe knock events and significant engine damage. SPI has been associated with fuel properties, lubricant composition, and engine design and operation. In this work, a single-cylinder test engine with a dry-sump oil system was utilized to study the SPI response of E10 and E25 fuels with a range of Reid Vapor Pressure (RVP). An automated test procedure was employed, consisting of ten square-waved load profile segments, with each segment composed of 5 min of low-load operation followed by 25 min of sustained high-load operation. These tests were replicated across multiple days of testing including a lubricant triple flush between tests, and an online Fuel in Oil diagnostic measurement. Exhaust particulate

Splitter, Derek, Jatana, Gurneesh, DelVescovo, Dan, Douvry-Rabjeau, Julien, Fioroni, Gina, Chapman, Elana, Salyers, John

Challenges to Ranking Diesel Fuels for NO _x Emissions Using a Constant-Volume Combustion Chamber

2026-01-0348

4/7/2026

The market is witnessing an unprecedented proliferation of low-emission fuel components. To effectively evaluate the suitability of these novel fuels for engine applications, fuel blenders and original equipment manufacturers require rapid and reliable assessment methodologies. Traditionally, such evaluations rely on comprehensive engine testing, which, while thorough, is both time-intensive and costly. In response to the growing diversity of emerging fuel options, this work aims to establish a streamlined screening approach capable of effectively replicating the outcomes of full-scale engine testing. We examined the use of a constant volume combustion chamber for the measurement of fuel effects on NOx emissions, with the goal of developing a method to rapidly screen or rank fuels in a small - volume experiment. A small amount of fuel was injected into air at 650°C and 20 bar, where it ignited and burned. The chamber was sampled post-combustion using a chemiluminescence NOx analyzer

Luecke, Jon, Rahimi, Mohammad, Mohamed, Samah, Naser, Nimal, Chausalkar, Abhijeet, McCormick, Robert

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

2026-01-0324

4/7/2026

The rapidly transforming mobility sector is confronted with a dual challenge: achieving market expansion while significantly reducing emissions. Even if vehicle electrification tends to be favored in developed nations, it is widely acknowledged that no single solution is universally optimal. Within this context, hydrogen emerges as a compelling energy vector. It can be used both in fuel cells and internal combustion engines. This latter benefits from a well-known architecture and existing production infrastructures constituting a viable short-term and cost-effective solution especially for light or heavy-duty and off-road applications. In this context, investigation on the hydrogen spark-ignited internal combustion engine was performed, focusing especially on critical abnormal combustions. Indeed, during early development phase, abnormal combustion management was a challenge requiring the identification of the root cause of these issues. This work, based on the use of a versatile

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

Experimental Evaluation of After-Treatment Solutions for Heavy-Duty Natural Gas Vehicles to Meet Future CNVII Regulations

2026-01-0376

4/7/2026

The heavy-duty truck market in China has seen a significant increase in the adoption of natural gas-powered engines over the past two years. Simultaneously, the anticipated release of the China VII emissions regulation proposal by the end of 2025 is expected to impose stricter emissions limits on all heavy-duty engines, including new particulate number (PN10) thresholds analogous to those in the Euro 7 regulation. While tailpipe oxides of nitrogen (NOx) and methane (CH4) emissions from natural gas engines can be mitigated through tighter lambda control and adjustments to catalyst volume and precious metal (PGM) loading, addressing NOx and particulate number (PN) emissions necessitate more advanced after-treatment solutions. Although natural gas combustion is virtually soot-free, the entrainment of lubricating oil into the combustion chamber, especially during cold-start conditions, poses a challenge, leading to potential exceedance of the proposed future China VII limits. Additionally

Gao, Jiahui, Besch, Marc, Ding, Ning, He, Suhao, Zhao, Yuxin, Yixiao, Li, Shen, Ye

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

2026-01-0278

4/7/2026

The demand for sustainable mobility and transportation is accelerating the adoption of alternative fuels, particularly hydrogen, in internal combustion engines. However, these engines present specific risks, such as flammable crankcase gas accumulation from blow-by and irregular combustion resulting from oil transport into the combustion chamber. Addressing these challenges requires advanced simulation tools to optimize power-cylinder-unit performance, specifically piston ring and gas dynamics. This study demonstrates the success of physics-based 2D simulation for hydrogen PCU design optimization, focusing on blow-by reduction and control of gas-flow-driven oil transport. Unlike commercial codes with adjustment and fitting parameters, the 2D simulation code – developed by Massachusetts Institute of Technology and successfully applied by MAHLE over decades – is fundamentally physics-based, enabling direct predictive capability without empirical calibration. Leveraging the validated

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

The Membrane Engine: Concept, Model, and First Results

03-19-01-0003

2/12/2026

This study investigates the feasibility of a novel internal combustion engine (ICE) architecture, termed the membrane engine, in which the conventional piston is replaced by a flexible elastic membrane. Although the concept appears in several patent documents proposing reduced friction, improved sealing, and lower heat losses, no empirical data has been published to support these claims. To the authors’ knowledge, this work presents the first membrane engine built and experimentally tested. The primary aim is to verify whether such an engine can operate as a functional ICE, regardless of its current efficiency or performance level. To support concept validation, a simplified mathematical model was developed to describe the membrane’s deformation and its effect on combustion chamber volume. Unlike conventional piston engines, the membrane introduces a pressure-dependent geometry, enabling a variable compression ratio. The model is not intended to predict performance but to assist in

Allmägi, Roland, Ilves, Risto

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

03-19-01-0006

2/9/2026

Recent literature has highlighted significant heat transfer losses and elevated particle formation in direct-injection hydrogen engines, particularly when compared to hydrocarbon fuels such as methane. These challenges are attributed to hydrogen’s unique physicochemical properties, notably its short flame quenching distance and high diffusivity, as well as the interaction between the hydrogen jet and lubricated cylinder surfaces, which promotes lubricant entrainment into the combustion chamber. Consequently, a fundamental understanding of these entrainment mechanisms is a prerequisite for developing engineering strategies to enhance thermal efficiency and mitigate particle formation. The reported study investigates gaseous jet–air interaction in a confined volume to elucidate the influence of injector geometry on jet propagation and air entrainment. Three distinct jet configurations were examined: the wide hollow-cone, the narrow hollow-cone, and the round jets. The jet evolution and

Ben David Holtzer, Ben Binyamin, Tartakovsky, Leonid

Improving Cold Start and Transient Performance of Medium BMEP CEV Stage V Engines at Low Ambient Temperature and Pressure

2026-26-0142

1/16/2026

Meeting the stringent emissions norms of CEV stage V for medium BMEP engines, CI engines present significant challenges, particularly concerning cold startability. Low ambient temperatures and pressures intensify the cold start difficulties which are characterized by prolonged cranking, incidences of misfiring, compromised transient response and overall engine performance. This paper highlights the strategies and technologies employed to enhance cold start and transient performance of medium BMEP engines under such demanding environmental conditions. Investigations were conducted up to an altitude of 4500m and ambient temperatures as low as-20°C, utilizing only air heater at intake manifold as the sole cold start aid. This cost effective approach is integrated with an optimized combustion chamber design, along with minimal pilot injection timing and quantity to facilitate smooth ignition and stable combustion during cold start. The paper also explore the techniques to improve the

Saxena, Harshit, Lokare, Prasad, Santhosh, Ajith, Gandhi, Naresh, Shinde, Prashant

Optimization of Negative Crankcase Pressure Mechanism to Minimize Oil Pumping into Combustion Chamber and Ensure Particulate Number Compliance in Euro VI Emission for Natural Aspirated Gas Engine

2026-26-0223

1/16/2026

Emissions regulations, such as Euro VI, drives the Automotive industry to innovate continuously in Engine development. One significant challenge is the engine oil pumping from the crankcase into the combustion chamber, where it participates in combustion, which contributes to increased Particulate Numbers and fails to meet Euro VI emission compliance. This issue is most noticeable during engine idling and motoring conditions. During this time, a higher negative pressure difference develops between the intake manifold, which is acting above the combustion chamber and the engine crankcase. This pressure difference drives oil-laden blow-by aerosols past piston rings during the intake stroke and through the valve stem seals, allowing oil into the combustion chamber. The impact of the pressure difference between the intake manifold and crankcase was studied by varying the crankcase pressure through crankcase ventilation system. The results confirm that oil entry into the combustion chamber

R, Mahesh Bharathi, Bondfale, Shubham, Jeyaprakasan, Dharoon Gautham

Evaluation of Intercooler Effectiveness with No Fan, Single Fan, and Dual Fan: A Simulation and Experimental Study

2026-26-0579

1/16/2026

Turbochargers play a crucial role in modern engines by increasing power output and fuel efficiency through intake air compression, thereby improving volumetric efficiency by allowing more air mass into the combustion chamber. However, this process also raises the intake air temperature, which can reduce charge density, lead to detonation, and create emissions challenges—such as smoke limits in diesel engines and knock in gasoline spark-ignited (GSL) engines. To mitigate this, intercoolers are used to cool the compressed air. Due to packaging constraints, intercoolers are typically long and boxy, limiting their effectiveness, especially at low vehicle speeds where ram air flow is minimal. This study investigates the use of auxiliary fans to enhance intercooler performance. Two methodologies were adopted: 1D simulation using GT-Suite and experimental testing on a vehicle under different fan configurations—no fan, single fan, and dual fans (positioned near the intercooler inlet and outlet

Patra, Somnath, Hibare, Nikhil, Ganesan, Thanigaivel, Gharte, Jignesh Rajendra

Development of High BMEP Natural Gas Engine with Knock Mitigation

2026-26-0121

1/16/2026

The stringent emission norms over the past few years have driven the need to use low-carbon fuels and after treatment technology. Natural gas is a suitable alternative to diesel heavy-duty engines for power generation and transportation sectors. Stoichiometric combustion offers the advantages of complete combustion and low carbon dioxide emissions. Turbocharging and cooled exhaust gas recirculation (EGR) technology enhances the power density along with reduced exhaust emissions. However, there are several constraints in the operation of natural gas spark ignition engine such as exhaust gas temperature limit of 780 °C, sufficient before turbine pressure for EGR drivability, boost pressure, peak cylinder pressure limit and knocking. These limits coulld restrict the engine BMEP (brake mean effective pressure). In the present study, tests were conducted on a V12, 24 liters, heavy duty natural gas fuelled spark ignition engine (600 HP) with different EGR and turbocharger configurations to

Khaladkar, Omkar, Marwaha, Akshey

Unveiling the Dynamics of Methanol-Diesel Dual Direct Injection Compression Ignition Combustion: A Synergistic Experimental and Numerical Study

2026-26-0110

1/16/2026

The pressing global need for de-fossilization of the transport sector, especially within the heavy-duty segment, has intensified the exploration of alternative clean fuels. In this context, methanol gained traction due to their renewable production pathways, carbon-neutrality, and are being highly promoted by the Indian government to reduce CO2 emissions. Dual direct injection compression ignition (DDICI) is an effective combustion strategy to use methanol in heavy-duty engines, which combines the advantage of high-efficiency compression ignition with the clean-burning potential of methanol. In contrast to spark-ignited premixed methanol engines, this strategy involves a diffusion combustion of the methanol flame, thereby eliminating knocking and enabling running with high compression ratios. This experimental and numerical study presents a comprehensive investigation into the DDICI strategy using methanol as primary fuel and diesel as a pilot for ignition assistance. The work

Singh, Inderpal, Dhongde, Avnish, Raut, Ankit, Güdden, Arne, Emran, Ashraf, Berry, Sushil

Combustion Chamber Pressure and Temperature Analysis Based on Heat Release Rate Parameters of a Spark Ignition Engine

2025-36-0082

12/18/2025

Internal combustion engines have been developed and widely used since the last century, and they continue to be extensively employed today. Engine development has progressed significantly, and due to the environmental impacts caused by their use, new technologies are being developed to reduce pollutant formation after the combustion process and to increase thermal efficiency. Computational modeling is a tool that has supported this development and can be categorized into three types: zero-dimensional, quasi-dimensional, and three-dimensional models. The 0D and 1D models offer a good balance between computational processing time and result uncertainty when compared to three-dimensional models. The Wiebe function is a simple analytical approach capable of describing the fuel burn rate in combustion engines. Previous studies have shown that applying this function yields results that accurately describe the apparent heat release rate in PFI engines.The present study aims to determine the

Souza Pereira, Felipe Augusto de, Araújo Moreira, Thiago Augusto de, Filho, Fernando Antônio Rodrigues

Combustion Chamber Geometry Comparison in Natural Gas Engines under Conventional and Dethrottled Operation

2025-36-0217

12/18/2025

Growing interest in cleaner energy has spurred progress in engine technology, focusing on greater efficiency and lower emissions. Methane-based fuels, like compressed natural gas (CNG), have become an alternative for spark-ignition engines, especially in Brazil. Among performance strategies, dethrottled operation stands out by reducing intake restrictions and minimizing pumping losses, a major inefficiency in conventional spark ignition engines. This improves thermal efficiency and reduces both fuel consumption and emissions. This study experimentally examines the performance and combustion of a CNG-powered Hyundai HR 2.5 16V engine, converted from diesel to spark ignition with natural gas, comparing factory (omega) and custom (reentrant) piston geometries under both conventional and dethrottled modes. The research evaluates how piston design affects combustion stability, efficiency, and emissions across different load strategies. Tests were conducted at 7, 8, and 9 bar loads, as well

Silva, Cristian Douglas Rosa da, Garlet, Roberto Antonio, Dapper, Jackson Mayer, Fagundez, Jean Lucca Souza, Lanzanova, Thompson Diórdinis Metzka, Martins, Mario Eduardo Santos

Methodology for Characterizing the Spray of an Internal Combustion Engine Fuel Injector

2025-36-0194

12/18/2025

This study presents a methodology for characterizing the spray of an internal combustion engine (ICE) fuel injector, focusing on direct injection (DI) systems. It addresses the knowledge gap in academic research regarding injector spray patterns by conducting experimental tests and numerical simulations. Using a Bosch HDEV 1.1 pressure swirl injector and EXXSOL D60 test fluid, spray characteristics were captured with a high-speed camera under varying injection pressures and ambient/counterpressure conditions. These experimental data were used to calibrate a numerical model for simulating spray dynamics within the combustion chamber. The research examines the impact of parameters such as breakup length and breakup size constant on spray behavior, revealing that the breakup size constant significantly affects spray penetration. The study successfully developed and validated a methodology for characterizing and modeling fuel injector sprays, providing a valuable reference for optimizing

Paula Araújo, Gabriel Heleno, Assis, Marcelo Suman Silva, Malaquias, Augusto Cesar Teixeira, Carvalho Torres Filho, Marcos, Baeta, José Guilherme Coelho

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

Tarnawski, Piotr

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

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

Knock Phenomenon Investigation in SI Engine Fuelled with Ammonia-Hydrogen Mixture

2025-01-0532

11/25/2025

Ammonia has emerged as a compelling carbon-free alternative fuel for applications in sectors such as power generation and heavy-duty transportation, where thermal energy conversion plays a dominant role. Its potential lies in its high hydrogen content, carbon-free combustion, and the feasibility of large-scale storage and transport. However, ammonia’s combustion behavior poses significant challenges due to its low reactivity, characterized by a low laminar burning velocity, high autoignition temperature, and narrow flammability range. These properties hinder stable and efficient operation in conventional internal combustion engines. A common strategy to mitigate these limitations involves blending ammonia with hydrogen—often generated via on-board catalytic cracking of ammonia—which improves ignition and flame speed. Despite these benefits, the presence of hydrogen increases the risk of knock, particularly in high-compression-ratio engines designed to improve thermal efficiency. This

Hurault, Florian, Brequigny, Pierre, Foucher, Fabrice, Rousselle, Christine

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

2025-01-0524

11/25/2025

Hydrogen is a promising alternative to conventional fuels for decarbonizing the commercial vehicle sector due to its carbon-free nature. This study investigates the ignition and flame propagation characteristics of hydrogen in a 2-liter single-cylinder optical research engine representative of the commercial vehicle sector. The main objective was to enable high power density operation while minimizing NOx emissions. For that, ultra-lean combustion was employed to lower in-cylinder temperatures, addressing the challenge of NOx formation. To counteract delayed and unstable combustion under lean conditions, an active pre-chamber ignition system was implemented. It uses a gas-purged pre-chamber with separate hydrogen injection and spark plug ignition. Turbulent hot gas jets from the pre-chamber ignite the fresh mixture in the main combustion chamber, enabling faster and more stable ignition compared to conventional spark plugs. Additionally, the low volumetric energy density of hydrogen

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

Sustainable Engines with Carbon-Neutral Fuels – Fast Adaptation for Efficient Multi-Fuel Operation by Tailored Charge Motion Design

2025-01-0534

11/25/2025

As a fundamental element of measures to reduce the carbon footprint of commercial applications, carbon-neutral fuels are increasingly coming into focus for heavy installations. In addition to diesel substitute fuels, alternative energy carriers like NG, H2, MeOH and NH3 are gaining increasing attention. The energy conversion of these fuels is typically taking place on the principle of premixed combustion, which places different demands on fuel injection and mixture formation, as compared to optimized diesel-like combustion. Accordingly, the demand to layout multi-fuel capable engine designs centers to a high share on the above-mentioned design that can burn these different fuels with high efficiency and support a high degree of commonality with the in-series engine to carry over reliable operation and to maintain attractive cost figures. FEV has developed the Charge Motion Design (CMD) process, which can be applied to design the intake ports and combustion chambers for multi-fuel

Koerfer, Thomas, Dhongde, Avnish, Boberic, Aleksandar, Zimmer, Pascal, Pischinger, Stefan

Optimization of Injection Parameters for a Free-Piston Engine Equipped with Flat-Head Combustion Chamber

2025-01-5075

11/11/2025

The free-piston engine represents a paradigm shift in internal combustion engine technology, with its unique structure promising efficiency gains. However, injection parameters are one of the core elements of free-piston engine performance. This study employs computational fluid dynamics analysis to optimize the spray cone angle and start of injection timing for a two-stroke dual-piston opposed free-piston engine equipped with a flat-head combustion chamber. A three-dimensional transient model incorporating dynamic adaptive mesh refinement was constructed by using CONVERGE 3.0 software. The results indicate that a spray cone angle of 25° achieves optimal fuel distribution, yielding a peak indicated thermal efficiency of 42.14% and an indicated mean effective pressure of 9.08 bar. Crucially, advancing the ignition timing to 215°CA improves mixture homogeneity but simultaneously increases peak cylinder temperatures and NOx. Conversely, delayed start of injection timings reduces NO

Xu, Zhaoping, Yang, Shenao, Liu, Liang

An Open-Source Solenoid Injector Driver Circuit for Fuel Injection Research

03-18-07-0041

11/10/2025

Common rail, high-pressure electronic fuel injection is one of the primary technologies enabling high-efficiency and low emissions in modern diesel engines. Most fuel injectors utilize an actively controlled solenoid valve to actuate a needle that modulates the fuel supply into the combustion chamber. The electrical drive circuit for the injector requires extensive development costs, and thus, most designs are proprietary in nature, making it difficult to perform academic studies of the fuel injection processes. This research presents an injector driver circuit to control one or more solenoid injectors simultaneously for research-based injector development efforts. The electrical circuit was computationally modeled and optimized iteratively, and then, electronic hardware was developed to demonstrate control of a Bosch CRIN3 solenoid diesel injector as proof of concept. In addition, the injector performance was quantified by the fuel rate of injection (ROI) profiles obtained in a test

Bogdanowicz, Edward, Agrawal, Ajay, Lemmon, Andrew N., Bittle, Joshua

Effect of EGR and Ethanol additive on Performance and Emission Characteristics of Diesel Engine Fuelled with Rubber Seed Biodiesel Blends

2025-28-0224

11/6/2025

Alcohol is being considered as an alternative to traditional fuels for compression ignition engines due to their oxygen content and biomass origin. Although alcohol generally has lower cetane numbers, which makes them more favorable for premixed combustion, they also offer potential for lowering emissions in internal combustion engines, particularly when combined with strategies such as exhaust gas recirculation (EGR). This research focuses on enhancing the performance of a single-cylinder, four- stroke diesel engine by introducing ethanol into the intake port during the intake phase. Diesel and rubber seed biodiesel were used as primary fuels and were directly injected into the combustion chamber. The findings indicated that adding ethanol to rubber seed biodiesel, along with 10% EGR, led to improved brake thermal efficiency and a reduction in NOX emissions. The ethanol injection timing and duration were optimized for effective dual-fuel operation. At full engine load, the highest

Saminathan, Sathiskumar, G, Manikandan, Bungag, Joel Quendangan, T, Karthi

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

2025-32-0081

11/3/2025

The development of next-generation hydrogen-fueled engines introduces critical challenges related to thermal loads within the combustion chamber, particularly in high-performance applications. To address the extreme temperatures encountered, effective piston cooling strategies, such as oil jet impingement, are essential. Accurately predicting thermal stresses to prevent component failure is therefore crucial. However, numerical simulations often come with significant computational costs. This paper presents a comprehensive multi-fidelity modeling approach to predict the thermal behavior of pistons under these demanding conditions. The model integrates a simplified 3D thermal representation of the piston, a lumped-parameter mechanical model of the piston-liner assembly, and convective boundary conditions obtained at various levels of fidelity, from high-level Computational Fluid Dynamics (CFD) simulations to literature correlations. Additionally, the study examines the influence of

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

Development of Automatic Calibration System for PFI Engines

2025-32-0084

11/3/2025

This report summarizes the research findings on fuel injection calibration methods, aiming to improve engine performance and reduce environmental impact. In Port Fuel Injection (PFI) engines, the injected fuel adheres to the port walls and mixes with air as it vaporizes, then flows into the combustion chamber. Traditionally, the fuel injection quantity is determined by the base map, which is calibrated for a steady state, and corrections for transient conditions. During steady-state operation, the air-fuel ratio of the mixture is uniquely determined by the amount of fuel injected, allowing for reproducible calibration. However, during transient conditions, the amount of fuel adhering to the walls and the amount vaporized do not balance, necessitating transient compensation to achieve the desired air-fuel ratio. Traditional transient compensation has been adapted for each engine model based on experience to accommodate differences in port shapes and injector placements. This approach

Haraguchi, Kazuki

Measurement of the Liquid Fuel Film on the Combustion Chamber Wall of a Gasoline Engine using a Novel Capacitive Sensor

2025-32-0018

11/3/2025

The reduction of exhaust emissions and particulate matter from internal combustion engines remains a critical challenge, particularly under cold start and warm-up conditions, where a significant portion of total emissions is generated. In spark-ignition (SI) gasoline engines, the formation of liquid fuel films on intake ports wall, piston and cylinder wall surface significantly contributes to unburned hydrocarbon and particulate emissions. Also, the fuel film adhering to the wall can be a cause of the lubricating oil dilution. To address these issues, a novel capacitive sensor, fabricated using MEMS technology, was developed and applied to investigate the behavior of liquid fuel films formed inside the combustion chamber of a single-cylinder engine. The sensor detects changes in capacitance caused by fuel film adhesion to the sensor surface. The sensor was installed in a single-cylinder test engine along with a direct fuel injector allowing for the controlled formation of fuel films on

Kuboyama, Tatsuya, Nakajima, Takeru, Moriyoshi, Yasuo, Takayama, Satoshi, Nakabeppu, Osamu

Experimental and Kinetic Study of Methane Blending on The Laminar Combustion and Emission Characteristics of Ammonia Under Various Oxygen Contents at High Temperature and Pressure

2025-32-0060

11/3/2025

As a carbon-free fuel, ammonia is one of the alternatives to traditional fossil fuels, but its combustion characteristics are poor, and it is usually optimized by blending methane and increasing oxygen content. However, there are few relevant studies under different conditions. In this study, the laminar burning velocities (LBV) and flame instability of NH3/CH4/O2/N2 mixture at high initial temperature (T), high initial pressure (p), various oxygen contents (Ω) and methane energy ratios (α) are analyzed using a constant volume combustion chamber (CVCC). Through numerical simulation, how various oxygen contents and methane energy ratios affect the combustion characteristics of NH3/CH4/O2/N2 mixture and NO emission is analyzed. The results show that LBV is positively correlated with T, α and Ω, and negatively correlated with p. Markstein length (Lb) does not change significantly with T, but increases with α and decreases with p and Ω. Both oxygen enrichment and methane blending

YU, Yuantao, Dai, Zhizhuo, Hou, Chunlei, Ye, Mingyuan, Zhang, Xiaolei, Cui, Zechuan, Yin, Shuo, Nishida, Keiya

Development of a Combined Injection and Ignition Unit for a Gas Engine with Direct Hydrogen Injection Integrated into the Standard Spark Plug Access Hole

2025-32-0059

11/3/2025

To achieve the desired fuel switch from natural gas to hydrogen in internal combustion engines for combined heat and power units, it is necessary to make some adjustments to the fuel supply system. External gas mixers increase the probability of backfiring when natural gas is replaced by hydrogen. In addition, the low density of hydrogen results in a loss of power. Therefore, direct gas injection is preferred when using hydrogen. A drawback of direct injection is the requirement of higher injection pressures to achieve the desired fuel mass and mixture homogeneity as well as the additional access to the combustion chamber for the direct gas injector in the cylinder head. This paper proposes an alternative approach that does not necessitate the implementation of a high-pressure direct injection system nor additional access to the combustion chamber via the cylinder head. A combined injection and ignition unit, called HydroFit, was developed which uses a sleeve inside the spark plug bore

Rischette, Nic, Holzberger, Sascha, Helms, Sven, Kettner, Maurice

Visualization Study on Combustion Characteristics of Ammonia/Methane/Air Mixtures Ignited by Diesel Pilot in Rapid Compression and Expansion Machine

2025-32-0054

11/3/2025

The application of ammonia fuel in engines can significantly reduce carbon emissions, serving as a crucial method for achieving carbon neutrality. However, its potential is hindered by the challenges of ammonia's difficulty in ignition and slow combustion rate. An effective solution to these drawbacks is to blend methane into ammonia mixtures and use a small amount of diesel for ignition. This study investigates the effects of mixture equivalence ratio and gas composition on the combustion characteristics of diesel-ignited NH3/CH4/Air mixtures. Pressure measurements and visual observations were conducted using a rapid compression expansion machine (RCEM). Experimental results reveal that the combustion process exhibits two distinct stages: initial intense diesel combustion followed by mixture combustion. Higher equivalence ratios prolong ignition delay while accelerate secondary combustion. Pure ammonia mixtures show incomplete lean combustion, while richer mixtures achieve more

Yin, Shuo, Dai, Zhizhuo, Zhou, Qingxing, Cui, Zechuan, Zhang, Xiaolei, Ye, Mingyuan, Ren, Yifang, Wang, Zhanpeng, Nishida, Keiya

Diesel Combustion Parameter Estimation via Machine Learning – A Comparative Study

2025-32-0041

11/3/2025

This paper presents an analysis and comparison of distinct approaches for data-driven combustion parameter estimation for Diesel engines. Thereby, characteristic quantities are modelled by a set of selected regression models and via a convolutional neural network (CNN). While the former use settings from the Engine Control Unit (ECU) as input, the latter works by processing the raw crankshaft vibration signal. The central point of this study is a broad evaluation of data-driven modelling for Diesel combustion. This includes whether using a signal recorded from individual combustion cycles achieves better representation of the target values than using operational parameters from the ECU which cannot reflect unforeseeable, stochastic phenomena within the combustion chamber. This was evaluated by assessing predictions of six combustion characteristics: the crank angle of 10, 50 and 90 percent mass fraction burned, Peak-Firing-Pressure, Combustion Duration, and Ignition Delay. In two

Ofner, Andreas Benjamin, Sjoblom, Jonas, Geiger, Bernhard, Haghir Chehreghani, Morteza

Effect of Plasma-Assisted Ignition on Combustion and Emission Characteristics of Two Stroke Engines with Different Fuels

2025-32-0030

11/3/2025

This study explores the effect of plasma-assisted ignition (PAI) on combustion stability and emissions in two-stroke spark-ignition engines. Two engine platforms were evaluated: a conventional single-cylinder two-stroke engine and a thermodynamically advanced opposed-piston two-stroke (OP2S) engine. The OP2S engine configuration offers reduced heat loss and higher power density due to its uniflow scavenging and favorable geometry, but suffers from high residual gas fraction, which increases ignition difficulty and combustion instability. To address this, nanosecond-pulsed PAI was applied in various spatial arrangements and discharge voltages, using both gasoline and a low-reactivity gasoline/DMC blend fuel. Spark ignition timing was held constant at the minimum advance for best torque across all tests. Combustion stability was assessed via indicated mean effective pressure (IMEP) and its coefficient of variation, while CO and HC emissions were measured as environmental indicators

Liu, Jinru, Yamazaki, Yoshiaki, Otaki, Yusuke, Kato, Hayato, Kobayashi, Daichi, Umegaki, Tetsuo, Asai, Tomohiko, Iijima, Akira

Numerical Analysis of Combustion Stability and Efficiency Improvement in Ammonia Engine Utilizing Passive Turbulent Jet Ignition (PTJI)

2025-32-0049

11/3/2025

Ammonia, a carbon-neutral fuel, is a promising candidate for next-generation engine applications. However, its low flame speed (~7cm/s) and prolonged ignition delay (~10ms at stoichiometric conditions) impose significant challenges in achieving stable and efficient combustion across varying operating conditions. At high-speeds, incomplete combustion due to limited residence time reduces efficiency, while at low-speeds, ignition instability and low combustion temperatures hinder reliable operation. To address these challenges, the Passive Turbulent Jet Ignition (PTJI) system has been proposed to enhance turbulence-driven mixing and improve ignition characteristics. This study focuses on optimizing a PTJI system for ammonia-fueled engines using a three-phase methodology. First, the 800cc 2-cylinder gasoline engine was modified for ammonia using numerical analysis, and a baseline analysis of the combustion characteristics was conducted. Next, a turbulent intensity study within the PTJI

Ju, Kangmin, Kang, Hyun-Ung, Kim, Jeong Hyeon

Full-Cycle CFD Modeling of a Wankel Engine for UAV Applications Tommaso Lucchini, Federico Ramognino, Giovanni Gaetano Gianetti

2025-32-0013

11/3/2025

Rotary engines offer a highly attractive solution for uncrewed aerial vehicles (UAVs) and portable power generation, thanks to their compact design, high power-to-weight ratio, fewer moving parts, and ability to operate on multiple fuels. Despite their promising advantages, these engines still require significant improvements to match the efficiency and lifespan of traditional reciprocating internal combustion engines. In particular, fuel consumption is impacted by heat losses due to the high surface-to-volume ratio of the combustion chamber, as well as the unfavorable interaction between the rotor and stator, which slows down flame propagation. To address these challenges, computational fluid dynamics (CFD) has become an important tool for the study and optimization of Wankel engines, providing insight into how fuel efficiency is influenced by the complex interactions between combustion chamber design, flame dynamics, flow characteristics, and turbulence distribution. This work

Lucchini, Tommaso, Gianetti, Giovanni, Ramognino, Federico, Cerri, Tarcisio, Marmorini, Luca, Buttitta, Marco

Effect of In-Cylinder Hydrogen Mixture Formation on Hydrogen Combustion

2025-32-0065

11/3/2025

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

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

Investigating the Influence of Intake Runner Configuration on Scavenging and Combustion Processes in Elliptical Rotor Engines

2025-32-0089

11/3/2025

Elliptical rotor engines (ERE), also known as X-engines, feature intake and exhaust ports located on the rotating rotor. As the rotor turns, these ports traverse the entire combustion chamber, sequentially completing the scavenging process in three distinct combustion chambers through coordination with the cylinder walls. This intake and exhaust characteristic significantly differs from the characteristic found in traditional Wankel rotor engines. This study established an optical elliptical rotor engine to obtain the in-cylinder flow field by using Particle Image Velocimetry (PIV) and constructed a CFD model based on the experimental results. Then the effects of two different intake runners on the scavenging and combustion process of ERE were investigated. The results indicated that: Due to structural limitations, the prolonged intake port opening duration results in significant gas backflow during the intake process. The curved intake runner exhibits a higher turbulent kinetic energy

Qin, Jing, Wang, Yingbo, Pei, Yiqiang, Yao, Dasuo, Deng, Xiwen

Approaches for Mechanical Development and Validation of Hydrogen Internal Combustion Engines

2025-01-0398

10/7/2025

Hydrogen Internal Combustion Engines (H2 ICEs) are seen as a viable zero-emission technology that can be implemented relatively quickly and cost-effectively by automotive manufacturers. The changed boundary conditions of a hydrogen-fueled engine in terms of mechanical and thermal aspects require a review and potential refinement of the design especially for the 'piston bore interface' (liner honing, ring and piston design) but also for other engine sub-systems, e.g. the crankcase ventilation system. The influence of oil entry into the combustion chamber is even more important in hydrogen engines due to the risk of oil-induced pre-ignition. Therefore, investigations of the interaction between friction, blowby and oil transfer into the combustion chamber were performed and are presented in this paper. During the investigations, experimental tests were carried out on a single-cylinder engine ('floating liner') and on a multi-cylinder engine. The 'floating liner' concept allows the crank

Plettenberg, Mirko, Gell, Johannes, Grabner, Peter, Gschiel, Kevin, Hick, Hannes

CFD and FE Toolset for Predicting Structural Temperatures in a Hydrogen Internal Combustion Engine

2025-01-0383

10/7/2025

Hydrogen has been identified as a promising decarbonization fuel in internal combustion engine (ICE) applications in many areas including heavy-duty on- and off-road, power-generation, marine, etc. Hydrogen ICEs can achieve high power density and very low tailpipe emissions. However, there are challenges; designing systems for a gaseous fuel with its own specific mixing, burn rate and combustion control needs, which can differ from legacy products. Being able to determine the thermal distribution and temperatures of the power cylinder components has always been critical to the design and development of ICE. SAE-2023-01-1675 [1] presented an analytical FE-based tool, and validation using both FE and CFD methods for a Euro VI HD Diesel engine converted to operate on hydrogen gas using direct injection. In this study, updated methods and investigations are presented for Hydrogen ICE including applicability of the Woschni heat transfer correlation, use of CFD thermal wall functions and a

Bell, David J., Shapiro, Evgeniy, Turquand d Auzay, Charles, Hernandez, Ignacio, Hynous, Jan, Kohutka, Jiri, Osborne, Richard, Penning, Richard, Tomiska, Zbynek

CFD Analysis of Knocking in Hydrogen-Fueled Spark-Ignition Engines with Large Eddy Simulation and Conjugate Heat Transfer

2025-01-0389

10/7/2025

In the pursuit of a carbon-neutral society, hydrogen-fueled power generation engines are gaining considerable attention. However, knocking remains a significant problem that hinders efficiency improvements in hydrogen-fueled spark-ignition (SI) engines. In particular, the large displacement engines, such as those used in cogeneration and distributed energy sources, often face issues with knocking. This is because, with a larger bore and lower rotational speed, there is a higher risk of auto-ignition occurring before the flame has spread throughout the combustion chamber. Knocking is a complex phenomenon influenced by several interrelated physical factors:1) Flow: the non-uniform distribution of fuel concentration and flow velocity within the cylinder; 2) Combustion: the non-uniform propagation of flames affected by the mixture's concentration and flow velocity distribution; 3) Heat Transfer: the non-uniform temperature of the unburned mixture resulting from the temperature distribution

Nomura, Kazutoshi, Suzuki, Keita, Imamori, Yusuke, Fuse, Azusa, Oda, Yuji, Nakano, Hiroki, Tsujimura, Taku, Suzuki, Yasumasa

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