This numerical study investigates a spark-ignited, two-stroke engine employing uniflow scavenging, flathead cylinder head design, and an exhaust valve system to identify the optimal bore-to-stroke (B/S) ratio for maximizing brake efficiency at fixed displacement. A single-cylinder prototype engine was constructed, and its experimental data validated a 1D GT-SUITE simulation model. This validated model was then utilized to simulate a full-scale, 1.5-liter displacement, horizontally opposed four-cylinder engine with supercharger-assisted boosting, intended for small aircraft propulsion. The simulations explored a range of B/S ratios from undersquare (0.7) to oversquare (1.5), maintaining a consistent brake power output of 60 kW at 3000 rpm and lambda 0.9. Results showed that increasing the B/S ratio enhanced brake efficiency from 26.0% at B/S=0.7 to 27.0% at B/S=1.5, largely due to reduced frictional losses attributed to shorter stroke and lower piston speeds, decreased heat transfer

Zanchin, Guilherme, Hausen, Roberto, Fagundez, Jean Lucca, Lanzanova, Thompson, Martins, Mario

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

2025-32-0050

11/03/2025

There is growing demand for energy utilization due to stricter environmental emission norms to reduce greenhouse gases and other threats posed due to the emissions are major motivation factors for researchers to adopt on strategic plans to decrease the usage of energy and reduce the carbon contents of fuels, the usage of hydrogen or blend of hydrogen with CNG as a fuel in internal combustion engines is the best option. As hydrogen has lower volumetric energy density and higher combustion temperature, pure hydrogen-fueled engines produce lower power output and much higher NOx emissions than gasoline-fueled engine at stoichiometric air-fuel ratio. Blending of hydrogen with CNG provides a blended gas termed as hydrogen-enriched natural gas (hCNG). hCNG stands for hydrogen enriched compressed natural gas and it combines the advantages of both hydrogen and methane. The addition of Hydrogen to CNG has potential to even lower the CNG emissions and is the first step towards promotion of a

Syed, Kaleemuddin, Chaudhari, Sandip, Khairnar, Girish, Sajjan lng, Suresh

Study on Combustion Detection of a Spark-Ignition Engine with Fuel Variation Using Various Sensors

2025-32-0052

11/03/2025

The use of alternative fuels, such as biofuels and synthetic fuels in small mobility engines has become more common these days. Although these fuels contribute to the carbon neutrality, it is known that they do not have a certain fuel composition, which significantly affects the combustion characteristics of an engine, such as knocking and combustion duration. Therefore, to get the most out of these sustainable fuels, it is necessary to develop engine systems that are highly robust to variations in fuel composition. To achieve this goal, a method to sense fuel characteristics onboard using sensors already widespread in use or can be installed inexpensively is required. Although in-cylinder piezoelectric pressure sensors are useful for research in the laboratory, it is not suitable for the use in commercial engines because of its high cost. Therefore, the use of other sensors should be considered. The purpose of this study is to experimentally analyze what information related to

Hayashi, Kohei, Kim, Jihoon, Yamasaki, Yudai

Predicting Transient Soot Emissions in Diesel Engines Using Physical and Machine Learning Models

2025-32-0017

11/03/2025

In recent years, diesel engine emissions regulations have been strengthened worldwide, necessitating the evaluation of regulatory values under transient conditions. Consequently, the need to assess transient states in the development of diesel engines has increased significantly. The evaluation using MBD (Model Based Development) is considered a promising method for achieving both low fuel consumption and simultaneous reduction of NOx and soot emissions. However, the mechanism of soot formation is complex, making it challenging to model mathematically directly. In this paper, hybrid machine learning approaches combining a physical model and a machine learning model are used to validate the prediction of soot emissions under transient conditions in a diesel engine with an EGR system. Various parameters such as fuel consumption and emissions predicted by the physical model are compared with measurements to validate the accuracy of the physical model. The prediction of soot emissions by

Kitamura, Takahiro, Matsuoka, Ayano, Suematsu, Kosuke, Okano, Hiroaki

Ultralightweight Emission Measurement Systems for Motorcycles: Accuracy and Practicality in RDE Testing

2025-32-0011

11/03/2025

Real Driving Emission (RDE) testing for motorcycles presents unique challenges due to the motorcycle’s lightweight construction, limited mounting space, and sensitivity to added mass and aerodynamic drag. Full-functional automotive Portable Emission Measurement Systems (PEMS), while highly accurate, are often impractical for two-wheelers as their weight and size can alter driving resistances, fuel consumption, and emission profiles, but also complicate installation and probably effect the drivability of the vehicle. To address these limitations, lightweight alternatives such as Mini-PEMS and ultralightweight alternatives such as Sensor-based Emission Measurement Systems (SEMS) offer compact, low-power solutions tailored for small vehicles. SEMS are typically equipped with lower cost sensors and low-tech gas conditioning systems compared to PEMS. Due to this these systems may not meet regulatory homologation requirements. Nevertheless, they provide justifiable accuracy for many real

Schurl, Sebastian, Lienerth, Peter, Japs, Leonid, Schroeder, Matthias, Schmidt, Stephan, Kirchberger, Roland

Knock Sensors for Two Wheelers Applications

2025-32-0079

11/03/2025

This paper describes the design and characteristics of the knock sensor. The sensor is already used as a commodity product for automotive applications and used by all automotive OEMs for spark ignited combustion engines. With the arrival of the electronic fuel injection on the two wheelers, further optimization of the combustion can be obtained. Although there are many publications on the engine knock strategy, little is known publicly about the sensor itself. The knock sensor is an accelerometer based on a piezoelectric component; it provides an analog signal of the engine vibration. The Electronic Control Unit will filter the signal according to a specific strategy and defines the presence and intensity of the engine knock. The ECU will act accordingly on the ignition timing. The inner structure as well as the mechanical and electrical interface are described in this article.

van Est, Jeroen, Prieu, Corentin

Forward-Looking SiL-Based Fuel Consumption Simulation for Dual-Clutch Transmission Software Evaluation

2025-32-0070

11/03/2025

Evaluating the impact of software changes on fuel consumption and emissions is a critical aspect of transmission development. To evaluate the trade-offs between performance improvements and potential negative effects on efficiency, a forward-looking Software-in-the-Loop (SiL) simulation has been developed. Unlike backward calculations that derive fuel consumption based solely on cycle speed and engine speed, this approach executes complete driving cycles as the Worldwide Harmonized Light-Duty Vehicle Test Cycle (WLTC) within a detailed SiL environment. By considering all relevant influencing factors in a dynamic simulation, the method provides a more accurate assessment of fuel consumption and emission differences between two versions of the transmission software. The significant contribution of this work lies in the high-fidelity integration of a real virtual Transmission Control Unit (vTCU) software within a comprehensive, validated forward-looking SiL environment. This approach

Kengne Dzegou, Thierry Junior, Schober, Florian, Rebesberger, Ron, Henze, Roman

Impact of Water Injection on Emission Formation in an HVO-Fuelled NRMM Engine

2025-32-0067

11/03/2025

Water injection in diesel engines is a well-known method of lowering combustion temperatures and thus reducing nitrogen oxide (NOx) emissions. In this study, the influence of water injection in hydrogenated vegetable oil (HVO) operation on NOx formation, particulate emissions and ignition delay is analyzed in comparison to diesel operation on a John Deere JD4045 tractor engine. Both the fuel (HVO) and the water injection system were designed as ‘drop-in’ solutions that enable rapid implementation to reduce emissions, even in existing vehicle fleets. The standard engine control unit of the JD4045 engine was therefore used for the tests. A single water nozzle was installed downstream the charge air cooler to integrate a water injection system. The three operating points of interest were: (1) low speed and high load without exhaust gas recirculation (EGR), (2) high EGR rates at low speed and medium load and (3) the engine's ‘sweet spot’ regarding the emission-tradeoff at high speed and

Fuhrmeister, Jonas, Mayer, Sebastian, Günthner, Michael

Methodology of Minimum Energy Starting for SI Engine

2025-32-0090

11/03/2025

In general-purpose small SI engines, it is necessary to reduce fuel consumption under operating conditions involving repeated starts and stops. In other words, the energy distribution during the transition from 0 rpm to idling speed is a crucial factor. At startup, the SI engine must be driven by a motor, and the electrical energy required should be minimized. However, the engine must accelerate during this process, and the required electrical energy is influenced by factors such as compression, friction, and moments of inertia. The purpose of this research is to experimentally clarify the conditions for minimum energy starting in SI engines. Specifically, the effect of the moment of inertia was eliminated by using a motor to maintain a constant engine speed, thereby enabling the isolation and measurement of electrical energy consumed by friction. The electrical energy required to overcome the moment of inertia can be determined by comparing it with the energy consumed when

Matsuura, Yusuke, Tanaka, Junya

RDE Testing of Small Motorcycle in Indian Road Conditions and Study the Impact of Instrumentation on Emission and Fuel Economy

2025-32-0075

11/03/2025

This paper presents measurement results of emissions and fuel economy on real-world driving of two-wheelers in India using a state-of-the-art FTIR PEMS technology. The study aimed to characterize the emissions profiles of a small motorcycle under typical Indian driving conditions, including congested urban traffic and highway driving. This is the continuation of the study conducted previously on bigger motorcycle using gas analyzer [1], with necessary adaptations to suit the specific conditions of Indian roads and traffic. Key parameters such as NOx, CO, CO2 and Fuel consumption were measured during real-world driving cycles and comparison is done with standard WMTC emission testing cycle. The findings of this study provide valuable insights into the actual on-road emissions of two-wheelers in India, which can be used to develop more accurate emission models and guide the development of cleaner and more efficient two-wheeler technologies. Key Considerations: Specifics of Indian Driving

Agrawal, Rahul, Jaswal, Rahul, Yadav, Sachin

Effects of Intake-Air Heating on a Light-Duty CNG-Diesel Reactivity-Controlled Compression Ignition Engine

2025-32-0003

11/03/2025

Reactivity controlled compression ignition (RCCI) is a promising low-temperature combustion strategy that offers high thermal efficiency with reduced nitrogen oxides (NOx) and soot emissions. However, at low loads, RCCI operation often suffers from incomplete combustion, leading to elevated partial combustion products, such as, unburned total hydrocarbons (THC) and carbon monoxide (CO) emissions. Intake-air heating is a potential strategy to address these issues by enhancing fuel reactivity and promoting more complete combustion. In this study, the effects of intake-air heating (from ambient to ~95°C) on performance, combustion, and emissions were experimentally investigated in a light-duty diesel engine operated in compressed natural gas (CNG)-diesel RCCI mode. Experiments were conducted at low and intermediate loads at various engine speeds. A single injection strategy was employed for low-load, while a double-injection strategy was used at intermediate-load operating condition s. CO

Navaneethakrishnan, P., Sarangi, Asish K, Suman, Abhishek, Sreedhara, Seshadri, Singh, Arvind Kumar

Development of Integral Forming for New “NMAX” YECVT Parts Using the Plate Forging Method

2025-32-0005

11/03/2025

Yamaha Motor Engineering Co., Ltd. provides plastic processing technology based on fuel tank press forming technology, and is developing various plastic processing methods, including forging, and developing mold equipment to realize them. This time, the core parts of the YECVT unit mounted on Yamaha Motor Co., Ltd.'s small premium scooter "NMAX" were not made by welding individual parts to each other, but by integrally forming them from a single thick plate using the cold forming method, resulting in lightweight, compact, high-strength, high-precision parts. By incorporating a composite plastic processing method that takes advantage of the characteristics of the material while making full use of analysis technology and mold technology, we were able to develop a composite plastic processing method (plate forging method) that creates new added value and mass produce it. In addition,this development has made it possible to achieve a thickness increase of 1.7 times the standard material

Hongo, Hironari, Tamaru, Shogo, Uda, Shinnosuke

Computational Investigation on a Boosted Uniflow Scavenged Direct-Injection Combustion Engine (BUSDICE) with Alcohol Fuels

2025-32-0027

11/03/2025

Alcohol fuels, produced from renewable energy sources, are considered a crucial solution for achieving life-cycle carbon neutrality in internal combustion engines. The Boosted Uniflow Scavenged Direct-Injection Combustion Engine (BUSDICE) exhibits significant potential for high thermal efficiency with an aggressive downsizing design. In this study, a computational investigation was carried out to assess the spray mixing and combustion characteristics of BUSDICE fuelled with methanol and ethanol, compared with gasoline, under a high-load condition. The injection duration of methanol and ethanol is significantly longer than that of iso-octane, leading to incomplete evaporation. The mixture exhibits an “outer-rich, central-lean” stratification pattern due to the short mixing time and swirl flow transportation for all three fuels. However, the prolonged injection of methanol induces stronger turbulence, which can enhance the local mixing. The spatial mixture stratification, particularly

Feng, Yizhuo, Lu, Enshen, Dong, Shuo, Keshtkar, Hossein, Wang, Xinyan, Zhao, Hua

Development of Supercharged Direct-Injection Two Stroke Engine with Intake and Exhaust Valve for Series Hybrid (2nd Report)- To Realize Lean Burn -

2025-32-0023

11/03/2025

The two-stroke engine, known for its small displacement and high performance, is space-efficient when installed in a vehicle. As such, incorporating two-stroke engines into HEVs is an effective way to reduce vehicle weight and optimize engine space. However, one downside is that the amount of unfired elements in the exhaust gas increases due to the air/fuel mixture being expelled into the exhaust system during the scavenging process. Moreover, combustion can become unstable due to the large volume of residual burned gases in the cylinder. To address these issues, we propose a two-stroke engine equipped with intake and exhaust valves that directly inject fuel into the cylinder. In our first report, we presented an engine design and method that enable high scavenging efficiency and stable combustion in a two-stroke engine [1]. In this second report, we share the results of our research aimed at improving fuel efficiency and achieving low emissions, all while maintaining the high

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

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

2025-32-0054

11/03/2025

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

Development of a Fuel Cell System for Small Mobility Applications with Severe Load Fluctuations

2025-32-0038

11/03/2025

In recent years, small electric mobility powered by fuel cells have been proposed as a way to achieve a carbon neutral society. One reason for the proposal is that fuel cells have an advantage over battery electric vehicle (BEV) in traveling range and refueling time. This study develops a hybrid system combining a fuel cell and a lithium-ion capacitor (LiC) for small electric mobility applications with severe load fluctuations. The proposed system achieves a 53% reduction in size, a 50% reduction in weight, and a 23% improvement in acceleration performance compared to a configuration using a lithium-ion battery (LiB) as the secondary battery, while also reducing load fluctuations in the fuel cell. Although LiCs tend to be compact, lightweight, and capable of high output, they have limited discharge capacity. To address this, a prototype hybrid system combining a fuel cell and an LiB was initially constructed to verify the system’s ability to suppress load fluctuations through current

Suzuki, Masaya, Nakata, Nobuhiro

Development of an Artificial Calibrator for Shift Program Optimization to Enhance Fuel Efficiency

2025-32-0082

11/03/2025

The calibration of automotive electronic control units is a critical and resource-intensive task in modern powertrain development. Optimizing parameters such as transmission shift schedules for minimum fuel consumption traditionally requires extensive prototype testing by expert calibrators. This process is costly, time-consuming, and subject to variability in environmental conditions and human judgment. In this paper, an artificial calibrator is introduced – a software agent that autonomously tunes transmission shift maps using reinforcement learning (RL) in a Software-in-the-Loop (SiL) simulation environment. The RL-based calibrator explores shift schedule parameters and learns from fuel consumption feedback, thereby achieving objective and reproducible optimizations within the controlled SiL environment. Applied to a 7-speed dual-clutch transmission (DCT) model of a Mild Hybrid Electric Vehicle (MHEV), the approach yielded significant fuel efficiency improvements. In a case study on

Kengne Dzegou, Thierry Junior, Schober, Florian, Rebesberger, Ron, Henze, Roman

Transient Helium Jet Evolution Using High Speed Schlieren Imaging

2025-32-0057

11/03/2025

The accelerating global shift towards decarbonised energy systems has positioned hydrogen as a highly promising carbon-free fuel. This study comprehensively investigates the macroscopic characteristics and temporal evolution of vortex ring trailing helium jets, serving as a surrogate for hydrogen, injected into a quiescent ambient environment using high-speed Schlieren imaging. This research addresses critical insights into fuel-air mixing dynamics essential for optimising hydrogen direct injection (DI) internal combustion engines. Analysis of helium jet tip’s topology revealed a three-stage evolution from an initial pressure-insensitive phase, dominated by pressure wave structures, to a momentum-driven, vortex-dependent growth stage, then to a fully developed stage. Specifically, the lower-pressure cases showed increased Kelvin-Helmholtz instability and distinct head vortex pinch-off at the final stage. Jet tip velocities transitioned from initial high, rapid pressure wave development

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

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

2025-32-0063

11/03/2025

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

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

Experimental Study on Hydrogen-Methane Co-Combustion in Small Gas Engines

2025-32-0055

11/03/2025

Hydrogen fuel has garnered significant attention as a key method for adapting internal combustion engines to a carbon-neutral society. Hydrogen is a carbon-free fuel that does not produce CO2 emissions during combustion. However, its wide flammability range and extremely low ignition energy present technical challenges when applied to internal combustion engines, such as the frequent occurrence of abnormal combustion phenomena like pre-ignition and knocking. Furthermore, the low energy density of hydrogen makes it difficult to achieve high power output. Additionally, hydrogen’s high adiabatic flame temperature and short quenching distance result in increased NOx emissions and cooling loss, which are further obstacles to its use. To address these issues, this study focuses on methane blending as a remedial approach. Experiments were conducted using a naturally aspirated engine with a premixed intake method to investigate the effects of methane-hydrogen blending. The following key

Tanaka, Kenta, Tani, Toshihiro, Sako, Takahiro

Analysis of Combustion Process in HVO-Hydrogen Dual-Fuel Operation Using Simultaneous Imaging of OH* and CH* Chemiluminescence

2025-32-0053

11/03/2025

This study investigated the combustion process in a hydrotreated vegetable oil (HVO)–hydrogen dual-fuel operation using simultaneous imaging of the OH* and CH* chemiluminescence in a rapid compression and expansion machine (RCEM). In this operation, hydrogen served as the primary fuel, ignited by a small quantity of pilot fuel. CH* chemiluminescence was primarily detected in the pilot fuel combustion regions, whereas OH* chemiluminescence was detected in both the pilot fuel and hydrogen combustion regions, enabling the separation of pilot ignition and hydrogen flame propagation. The combustion mechanism was found to proceed through four distinct stages: autoignition of the pilot fuel, combustion of the mixture in the lean pilot fuel region, propagation of the hydrogen–air premixture flame, and flame propagation toward the wall and squish area. Furthermore, the effects of the pilot injection parameters on the combustion characteristics were systematically evaluated by varying the

Yukitani, Takumi, Une, Naoto, Mukhtar, Ghazian, Horibe, Naoto, Kawanabe, Hiroshi, Koda, Kazuyuki, Hiraoka, Kenji

Hydrogen-Assisted Renewable Fuels RME and HVO in the Compression-Ignition Engine

2025-32-0048

11/03/2025

The article presents the research results on performance, thermodynamic parameters, and toxic exhaust emissions from the combustion in a compression-ignition engine fueled optionally by the hydrotreated vegetable oil (HVO) or the rapeseed methyl ester (RME), both with hydrogen addition. Furthermore, regular diesel fuel was used to obtain the reference data for making comparisons between HVO, RME, and diesel fuel. Hydrogen was injected into the intake manifold of a compression-ignition (CI) engine. Typically, diesel fuel combustion in a CI engine initiates through its self-ignition, usually simultaneously occurring at many points across the engine cylinder. Hydrogen, as a very chemically reactive substance, can promote pre-ignition reactions and accelerate flame kernel formation, shortening the ignition lag. This is crucial for the smooth running of the compression-ignition engine. Hydrogen was added at amounts not exceeding 7% by volume (35% energy content) referred to air sucked into

Szwaja, Stanislaw, Juknelevicius, Romualdas, Pukalskas, Saugirdas, Rimkus, Alfredas, Szymanek, Arkadiusz

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

2025-32-0046

11/03/2025

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

Salim, Naqib, Beltaifa, Youssef, Kettner, Maurice

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