Browse Topic: Single cylinder engines

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Spray–Wall Interaction at Thermal Swing Coatings in SI Engines03-19-03-00146/25/2026
As a contribution to the reduction of greenhouse gas emissions in the transportation sector, the indicated efficiency of SI engines can be increased via thermal swing coatings. Thereby, a decrease in greenhouse gas emissions can be achieved, although not at all operating conditions. Here, the often-observed increased hydrocarbon emission partially overcompensates the reduced wall heat losses. The main root cause is always attributed to the increased surface roughness and porosity, leading to an increased crevice volume. Further investigations were performed at a single-cylinder engine equipped with a FTIR for species analysis of hydrocarbon emissions. A comparison of direct injection and port fuel injection were performed for RON95 E10 and methanol to assess the influence of mixture preparation. 3D CFD was used to additionally investigate the in-cylinder processes. The comparison of port fuel injection and direct injection showed a significant influence on the fuel hydrocarbon emissions for the direct injection when the thermal swing coating was applied. The effect is more pronounced for methanol. For port fuel injection nearly the same or reduced fuel hydrocarbon emissions can be observed. This is mainly attributed to an increased wall film agglomeration at the piston for the thermal swing coating in case of direct injection, which can be observed in 3D CFD. Due to the low thermal effusivity of the coating, the droplet impingement leads to a notable decrease in the surface temperature. This results in lower evaporation of the fuel and a longer droplet lifetime. Consequently, a fuel wall film is still present at top dead center after ignition leading to additional hydrocarbon emissions.
Fischer, Marcus, Pischinger, Stefan
A Holistic CFD Methodology for Full- and Multi-Cycle Simulation of Hydrogen Direct-Injection Internal Combustion Engines2026-37-00166/9/2026
Hydrogen is emerging as a viable energy carrier for the decarbonization of internal combustion engines (ICEs), representing a necessary step toward the long-term sustainability of this technology. In particular, hydrogen direct injection (DI) operation is receiving increased attention due to its inherent advantages over port fuel injection (PFI), such as reduced risks of abnormal combustion, higher specific power, and improved thermal efficiency. However, the mixture preparation process in DI operation generally leads to a stratified charge, especially under intermediate-to-late injection strategies, which in turn strongly affects ignition, combustion performance, and engine-out emissions. Therefore, investigating mixture formation, its key influencing parameters, and the resulting effects on the combustion process is essential for the proper design and optimization of hydrogen-fuelled DI ICEs. In this context, computational fluid dynamics (CFD) emerges as a powerful tool to address this research gap. Nevertheless, the numerical simulation of hydrogen DI ICEs presents several challenges, mainly related to the high pressure ratios across the injector nozzle, which generate under-expanded hydrogen jets with complex shock structures, as well as to the combustion behaviour of lean air–hydrogen mixtures characterized by thermo-diffusive instabilities. Consequently, the development of a high-fidelity and computationally efficient CFD methodology is a key requirement. In this work, a retrofitted single-cylinder engine (SCE) equipped with a hollow-cone injector is simulated over the entire engine cycle, considering operation under a moderately late DI strategy. First, the proposed 3D-CFD methodology is validated against the engine experimental data to assess its predictivity. The same operating condition is then investigated through multi-cycle simulations to evaluate numerical stability and analyse convergence behaviour. The results show that the air–hydrogen mixture is highly stratified at ignition timing, yet the methodology accurately captures the in-cylinder pressure and heat release rate evolution, also across multiple engine cycles.
Capecci, Marcolucio, Lucchini, Tommaso, Sforza, Lorenzo, Pezza, Vincenzo, Tosi, Sergio
Experimental Study of Knock Resistance Offered by Direct Water Injections in a Single-Cylinder Spark Ignition Engine03-19-02-00114/11/2026
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
Analysis of In-Cylinder Flow for Hybrid Gasoline Engine using High-Speed Particle Image Velocimetry2026-01-02984/7/2026
To increase the thermal efficiency of a hybrid inline 4-cylinder direct injection engine, combustion promotion was carried out by enhancing the in-cylinder flow. The intake port and piston top shape were optimized using CFD. In-cylinder flow analysis in steady flow showed that the mean steady flow tumble ratio with the in-cylinder flow enhancement specification increased to 1.7 compared to 1.0 with the previous model and 1.4 with the early development specification. The limit engine speed, which is the engine speed at when the mean flow coefficient decreases due to the choke, and the mean steady flow tumble ratio with the in-cylinder flow enhancement specification were positioned on the trade-off line between the NA and the TC engine. In-cylinder flow analysis on the single-cylinder optical engine showed that the in-cylinder flow entering the cylinder smoothly flowed to the exhaust side, and the in-cylinder flow descending on the exhaust side was smoothly converted to the upward flow by the piston top. Thus, the tumble ratio with the in-cylinder flow enhancement specification in the latter half of the compression stroke increased from 1.0 to 1.7 compared to the early development specification. Turbulent analysis was performed by applying the time filter method, a turbulence decomposition method proposed by the authors, to the in-cylinder flow field. The turbulent kinetic energy with the in-cylinder flow enhancement specification in the latter half of the compression stroke increased by 21.9%. The flame structure was located in the corrugated flamelets region on the turbulent premixed diagram, and the combustion promotion effect by in-cylinder flow enhancement was expected. Evaluation of combustion characteristics on the metal engine showed that the initial combustion duration with the in-cylinder flow enhancement specification decreased by 2.3 deg., the main combustion duration decreased by 4.4 deg., and the time loss decreased by approximately 2%. Therefore, the indicated thermal efficiency increased from 41.9% to 42.2%, proving the concept of combustion promotion by in-cylinder flow enhancement.
Okura, Yasuhiro, Urata, Yasuhiro
Advancing Oil Consumption Prediction with 3-D Multiphase CFD: Insights into Piston Design Impacts2026-01-02824/7/2026
Engine oil consumption contributes to hydrocarbon and particulate emissions, catalyst degradation, and reduced thermal efficiency. Reducing it is essential for meeting emission standards and improving engine reliability. This study introduces a 3-D Computational Fluid Dynamics (CFD) framework that captures micron-scale gaps in the piston-ring-cylinder system while accounting for ring dynamics. The model leverages Simerics-MP+ features—including a novel mesh motion strategy and Mismatched Grid Interface (MGI) coupling—to resolve fine crevice regions alongside coarser bulk domains. It incorporates piston translation, ring motion, and crankshaft rotation, and uses the Volume of Fluid (VOF) method to capture multiphase interactions in thin oil films. Compared to experiments, this approach offers detailed flow visualization in optically inaccessible regions at lower cost and complexity. Unlike traditional 1-D models, it captures nonlinear behaviors without relying heavily on parameter tuning. Applied to a single-cylinder engine, the model evaluates oil transport in two piston designs under fixed RPM and undeformed bore conditions. Results highlight piston geometry’s role in oil consumption, and qualitative validation against experiments confirms the model’s predictive capabilities. This CFD framework provides valuable insights to guide low-emission, high-efficiency engine design.
Mohapatra, Chinmoy K., Schlautman, Jeff, Manne, Venkata Harish Babu, Schroeder, Debera, Srinivasan, Chiranth
Optimal Strategies for SI H2 Combustion System and Pre-Ignition Investigation through Advanced Optical Techniques2026-01-03244/7/2026
The rapidly transforming mobility sector is confronted with a dual challenge: achieving market expansion while significantly reducing emissions. Even if vehicle electrification tends to be favored in developed nations, it is widely acknowledged that no single solution is universally optimal. Within this context, hydrogen emerges as a compelling energy vector. It can be used both in fuel cells and internal combustion engines. This latter benefits from a well-known architecture and existing production infrastructures constituting a viable short-term and cost-effective solution especially for light or heavy-duty and off-road applications. In this context, investigation on the hydrogen spark-ignited internal combustion engine was performed, focusing especially on critical abnormal combustions. Indeed, during early development phase, abnormal combustion management was a challenge requiring the identification of the root cause of these issues. This work, based on the use of a versatile single-cylinder engine, is dedicated to the optimization of hydrogen combustion through adaptations of injection strategy to minimize the NOx production and improve the combustion efficiency. A dedicated attention was paid to study the effects of different parameters of the hydrogen injection system, such as the location of the injector, the targeting and the injection pressure. Subsequently, a specific cylinder head has been designed to allow endoscopic optical access into the combustion chamber for a visualization of the combustion related phenomena using a high-speed UV intensified camera. The work was especially focused on abnormal combustion analysis such as pre-ignition and allows to analyze the behavior of different spark plugs. Different injection configurations were tested and their effects on combustion were evaluated using both adiabatic heat release rate analysis and in-cylinder movies obtained through the optical setup described above. It provides valuable data about mixture preparation, flame propagation and cycle to cycle fluctuations. Conventional heat release rate analysis gives macro level data of the combustion stroke whereas the endoscopic images provide 2D flame fields that enhance the understanding of the combustion characteristics. This work finally leads to a better understanding of abnormal combustion occurrences and guides towards the choice of relevant injection and ignition strategies, especially at full load.
Londos, Benoit, Bardi, Michele, Serrano, David, Laget, Olivier, Gautrot, Xavier, Bramoullé, Clément, Cordier, Matthieu
Investigation of In-Cylinder Cycle-to-Cycle Variation Using PIV, LIF and RANS Simulation2026-01-02994/7/2026
Cycle-to-cycle variation (CCV) of combustion is an issue that inevitably arises in internal combustion engines. There is a need to clarify and improve the situation, as well as predict it using computational fluid dynamics (CFD). This study involved carrying out experimental analyses of the factors that cause combustion cycle fluctuations, as well as predicting the CCV of gas flow using RANS. To elucidate the CCV in gas flow and combustion within gasoline engine, simultaneous TR-PIV, PLIF and direct-photography of flame propagation were performed using an optical single-cylinder engine, CCV prediction model for gas flow using RANS was verified. The results revealed the following: The variation in the equivalence ratio per cycle has little effect on initial combustion but does influence IMEP. Evaluating the laminar flame speed, SL and turbulent flame speed, ST as factors determining initial combustion revealed almost no correlation with SL, while moderate correlations were observed between ST and CA10. The position of the tumble vortex center at ignition timing was found to be critical; the vortex center position most favorable for advancing combustion timing was located to diagonally below the spark plug. The angular velocity at the center of the tumble vortex in the ensemble averaged flow significantly affected the turbulence kinetic energy (TKE) at the ignition timing, initial flame propagation speed, and CA10 phase. A model predicting cycle fluctuations during non-combustion was developed and verified against experiments. The CCV predicted using the spatial-based model reproduced the experimental CCV trends.
Hokimoto, Satoshi, Moriyoshi, Yasuo, Kuboyama, Tatsuya
Experimental Analysis and Numerical Simulation of the Performance Parameters of Tire Pyrolytic Oil in a Compression Ignition Engine2026-01-03454/7/2026
The search for alternative solutions for non-fossil fuels has led to several studies worldwide. This study focuses on environmentally responsible solutions to accelerate tire degradation, focusing on the transformation of these residues into fuel for diesel engines. The objective of this study was to experimentally evaluate, through numerical simulation, the performance of a compression ignition engine operating with pure diesel S10 fuel, crude and refined tire pyrolytic oil, and mixtures in proportions of 20, 40, 60, 80 and 100% with diesel oil. The experimental tests were performed on a single-cylinder engine coupled to a dynamometer bench, and the numerical simulation was performed using the Diesel Engine RK software. The experimental results indicated that increasing the proportion of refined pyrolytic oil in diesel slightly improves engine performance up to approximately 2750 RPM, after which the performance is reduced compared to pure Diesel. The addition of crude pyrolytic oil slightly improves engine performance throughout the engine operating range compared to pure diesel. The simulation results revealed performances similar to those obtained experimentally, with a highlight on the 20% blend ratio, which behaved similarly to Diesel. The research is relevant because valuable results were obtained in the search for more sustainable alternatives in the context of compression ignition internal combustion engines.
Santana, Claudio Marcio, Prudente, Lucas Rhuan, Leal, Elisangela M, Rocha, Ana Maura, Peixoto, Claudio
Influence of Lubrication Oil on Hydrogen Fuel-Share Combustion in a Conventional Medium-Speed Marine Diesel Engine2026-01-50142/23/2026
Carbon-free fuels present a potential solution for achieving climate-neutral operation of marine engines. However, their availability is minimal at the moment, though a steady increase can be expected in the coming years. During this transition phase, engine concepts that offer conventional diesel operation and a partial blending of alternative fuels to substitute diesel become interesting. This can be achieved, for example, by blending hydrogen in the intake air of a diesel engine, known as hydrogen fuel-share. Due to the high reactivity of hydrogen, its use in engines is limited by abnormal combustion phenomena (e.g., pre-ignition, knocking combustion), which current research on pure gas engines has shown to be strongly promoted by lube oil reactivity. Building on these fundamental investigations, this paper examines the influence of lubricating oil on the combustion characteristics of a H2 fuel-share medium-speed diesel engine and quantifies the potential to increase the hydrogen share using a less reactive engine oil. For this purpose, single-cylinder engine tests were conducted and supported by 0D/1D simulations with GT-Power and Cantera. The engine was configured as a conventional medium-speed marine diesel, equipped with a hydrogen port fuel injection (PFI) system on the cylinder head. A thermally stable ester-based gas engine oil was used for reducing reactivity compared to a state-of-the-art mineral diesel engine oil. The results show reduced auto-ignition tendency during compression and a mitigation of backfire. An increase in average effective CO2 reduction of up to 17 percentage points is demonstrated, resulting in a total CO2 reduction of 39% on a standard load profile for main propulsion engines. These findings highlight that the choice of lubricating oil can play a key role in increasing the hydrogen share in H2 fuel-share diesel engines, thereby supporting the transition toward climate-neutral propulsion concepts.
Achenbach, Tobias, Meinert, Robert, Mahler, Kay, Kunkel, Christian, Rösler, Sebastian, Prager, Maximilian, Jaensch, Malte
Potential of a Hydrogen Fuel-Share Combustion Concept for a Conventional Medium-Speed Marine Diesel Engine2026-01-50072/2/2026
To meet the International Maritime Organization’s (IMO) short-term greenhouse gas (GHG) reduction targets, partial decarbonization of the existing fleet, often powered by medium-speed diesel engines, is required. One approach for reducing CO2 emissions is to enrich the charge air with hydrogen to substitute diesel. However, hydrogen’s high reactivity can lead to combustion abnormalities such as backfire, pre-ignition, and knocking, thus limiting the feasible admixture rates. These challenges are particularly relevant in medium-speed diesel engines designed for high power output and efficiency at low rpm. While hydrogen fuel-share has previously been tested in small-bore engines at moderate loads, this study investigates the influence on combustion and achievable hydrogen admixture rates in a medium-speed, 4-stroke diesel engine operating with up to 30 bar net indicated mean effective pressure (net IMEP). To minimize retrofitting efforts and to preserve diesel performance, the investigations were conducted on a single-cylinder engine with representative design features of a conventional diesel engine: a high compression ratio, Miller valve timing, valve overlap, and a piston with deep valve pockets. The piston ring system is suited for heavy fuel oil (HFO) operation. Hydrogen was supplied via a port fuel injection (PFI) system. 0D/1D process simulations supplement the experimental data. Findings indicate that energetic hydrogen admixture rates of up to 43% are achievable at low loads, limited by an advancing start of combustion, and up to 15% hydrogen share at high loads, constrained by backfire. This results in an average CO2 reduction of ~22% on the E2 cycle for constant-speed main propulsion engines. Due to rising NOx emissions, the results are only applicable when meeting IMO Tier II limits with selective catalytic reduction (SCR). The results demonstrate that conventional medium-speed diesel engines are suited for hydrogen fuel-share operation and that CO2 reductions comparable to liquid natural gas (LNG) conversions are feasible.
Achenbach, Tobias, Meinert, Robert, Mahler, Kay, Kunkel, Christian, Rösler, Sebastian, Prager, Maximilian, Jaensch, Malte
Comprehensive Evaluation and Development of a Single Cylinder Engine Vehicle for Refinement of NVH Characteristics2026-26-03081/16/2026
The scale of worldwide population presents its own set of difficulties, especially in densely populated cities. Almost every individual has some form of personal transport, which leads to congestion and limited parking space. Automotive manufacturers are scaling down the size of vehicles to resolve these issues to some extent. This paper is based on the NVH development of a single cylinder diesel engine vehicle. It provides an insight into the comprehensive vehicle level NVH refinement approaches adopted. The NVH characteristics of benchmark two-cylinder diesel and baseline vehicle were measured and analyzed for target setting. The performance of each subsystem such as engine mounting, vehicle structure, intake and exhaust was evaluated, and gap analysis was performed against set targets. It was found that the engine mounting system and vehicle structure were inefficient in isolating the excitation forces. The design and location of the mounting system was evaluated using CAE and modified to improve modal performance and force isolation. The vibrations were evident at tactile locations and found to correlate with engine excitation frequency at certain locations. Hence, cradle and body structure analysis were carried out to reduce vibration transfer. Additional stiffeners and channels were added to vehicle structure which helped in eliminating problematic frequencies and noise levels. The acoustic pack of the vehicle was updated to reduce airborne transfer of noise and improve sealing of vehicle. The intake system was evaluated and the air filter with resonator size and position were modified to improve noise levels. Similarly, the exhaust muffler design was analyzed and modified to improve noise levels. Each modification was implemented and evaluated for its individual contribution in improving noise and vibration by validating on mule vehicle. After implementation of all feasible updates, the noise and vibration targets were achieved for the new vehicle.
Ghale, Guruprasad Chandrashekhar, Baviskar, Shreyas, Bendre, Parag, Kamble, Pranit, Bhangare, Amit, THAKUR, SUNIL, Kunde, Sagar, Wagh, Sachin
Optimization of Biogas Combustion in SI Engines Applied to the Pre-Chamber Ignition System2025-36-020912/18/2025
The diversification of the energy matrix, combined with the use of renewable and less polluting fuels in internal combustion engines, has encouraged numerous research efforts both nationally and internationally. In this context, the utilization of waste for biofuel production stands out as a promising alternative, offering a clean and economically viable energy source. Biogas is one of the most sustainable options and has been widely used in the industry. However, it presents low lower heating values (LHV) and difficulties in burning stoichiometric mixtures, which compromise engine performance, resulting in higher specific fuel consumption and lower power output compared to fossil fuels. To address this challenge, this study aimed to improve biogas combustion in internal combustion engines by investigating the application of a new pre-chamber ignition system in the combustion process and engine performance parameters. For this, experimental tests were conducted with two biofuel concentrations for evaluation: (100% CNG) and (85% CNG + 15% CO2), enriching the stoichiometric mixture and applying calibration methodologies in a single-cylinder engine adapted to operate with biogas, assessing engine performance parameters and gas emissions. The application of pre-chamber ignition showed significant improvements in energy efficiency, resulting in approximately a 12% torque gain in stoichiometric mixtures, contributing to more efficient combustion and a reduction in hydrocarbon emissions. The use of mixtures in the range of 1.0 to 1.2 led to emission reductions between 60% and 35% compared to the engine without the pre-chamber, demonstrating the pre-chamber’s ability to promote more complete combustion even in leaner mixtures. The data obtained provide valuable insights for the development and application of new technologies in biogas-powered internal combustion engines, contributing to advancements in this research area.
Siqueira, Caio Henrique Moreira, Ázara, Luiz Eduardo Martins, Ribeiro, José Vitor Puttini, Soares, Gabriel Faria, Silva, Fábio Moreira, Alvarez, Carlos Eduardo Castilla
Sustainable Engines with Carbon-Neutral Fuels – Fast Adaptation for Efficient Multi-Fuel Operation by Tailored Charge Motion Design2025-01-053411/25/2025
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 cylinder heads in the initial phase. This advanced methodology features the capabilities to predict the performance of different configurations for the various fuels based on condensed and simplified CFD simulations and dedicated post-processing routines. These correlations are tuned and calibrated to representative engine data for individual fuels to determine the characteristics. This paper highlights the detailed application of the CMD process for cylinder head and combustion chamber definition on the base of measurements on a state-of-the-art modular single-cylinder HD engine. Six configurations of the port designs and charge motion concepts were investigated. A comparison of the concepts was first performed with the CMD fuel correlations for H2. Three concepts with varying degrees of tumble were chosen for further detailing. The results of the case study are presented along with supporting engine measurements. In addition to previously tuned correlations, new measurements with NH3 were used to calibrate and synchronize the correlations of the CMD process. A dedicated variant of the DI H2 injection in addition to the ammonia port injection was investigated as well. The CMD fuel correlations were correlated to the testing data and later applied to all configurations to evaluate their performance and suitability. This technical study highlights the potential of CMD-driven design to enable flexible, efficient, and cost-effective multi-fuel combustion.
Koerfer, Thomas, Dhongde, Avnish, Boberic, Aleksandar, Zimmer, Pascal, Pischinger, Stefan
Development of a Comprehensive Predictive QD Knock Simulation Model for Hydrogen, Methanol, and an Ammonia–Hydrogen Blend2025-01-052811/25/2025
To support the transition toward climate-neutral mobility and power generation, internal combustion engines (ICEs) must operate efficiently on renewable, carbon-neutral fuels. Hydrogen, methanol, and ammonia-hydrogen blends are promising candidates due to their favorable production pathways and combustion properties. However, their knock behavior differs significantly from conventional fuels, requiring dedicated simulation tools. This work presents a modeling framework based on quasi-dimensional (QD) engine simulation, including two separate knock prediction models. The first model predicts the knock boundary of a given operating point and combines an auto-ignition model with a knock criterion. The overall methodology was originally developed for gasoline and is here adapted to hydrogen, methanol, and ammonia-hydrogen blends. For this purpose, the relevant fuel properties were incorporated into the auto-ignition model, and a suitable knock criterion was identified that applies to all investigated fuels. The model was validated using experimental data from single-cylinder engine tests. In addition, two entirely new modeling approaches were developed to predict statistical knock values, specifically knock frequency and knock intensity. Each model was calibrated once per fuel and subsequently validated across a wide range of conditions. The results show that the adapted knock boundary model and the new statistical model accurately capture the knock behavior of hydrogen, methanol, and ammonia-hydrogen blends. The methodology enables predictive knock analysis using QD simulation and supports the development of robust, high-efficiency ICEs for future carbon-neutral applications.
Benzinger, Steffen, Yang, Qirui, Grill, Michael, Kulzer, Andre Casal, Plum, Lukas, Hermsen, Philipp, Günther, Marco, Pischinger, Stefan, Hurault, Florian, Foucher, Fabrice, Rousselle, Christine
Firing TDC Identification Through Wasted Spark Duration Measurements During Cranking of Small Engines2025-32-008511/3/2025
Implementing control techniques through “virtual sensors” is extremely attractive for small size engines, given that cost effectiveness is essential. This work presents a routine for identifying the firing TDC through measurement of spark duration. Previous capability of correctly identifying cycle phasing through this route was confirmed during normal operation of a power unit that featured a wasted spark ignition system. Starting with the hypothesis that this could be implemented during engine cranking, the procedure was adapted for identifying the firing TDC as quickly as possible; it was also developed with the specific task of requiring less time for synchronization, compared to the previous version. The new method was verified on a small size 50 cc single cylinder engine that featured a recoil starter mechanism. Correct identification was confirmed, with the possibility of generating the reference signal as early as the 2nd cycle that featured normal operation of the ignition system; to put things into perspective, a minimum of 5-6 such cycles were recorded during multiple cranking events. Compared to the rpm based evaluation, more consistent identification could be achieved, mostly due to the fact that the spark duration measurements were influenced less by the varying engine speed during cranking.
Irimescu, Adrian, Merola, Simona
Measurement of the Liquid Fuel Film on the Combustion Chamber Wall of a Gasoline Engine using a Novel Capacitive Sensor2025-32-001811/3/2025
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 the sensor surface. Ethanol was used as the injected fuel for film formation due to its higher permittivity compared to iso-octane, the fuel used for engine operation. This choice enhanced the sensor sensitivity to film presence. Four experimental configurations were tested, varying the sensor’s location (intake vs. exhaust side) and whether the ethanol spray directly impinged on the sensor. The engine was operated at 2000 rpm with an intake pressure of 90 kPa. The coolant temperature was varied from 20 °C to 80 °C to simulate cold start and warm-up conditions. The transition from motoring to firing operation was used to replicate transient startup behavior, and the sensor output was monitored cycle-by-cycle. Results showed that the sensor effectively captured the formation and evaporation of the fuel film. Sensor output was significantly higher at locations exposed to direct ethanol spray, particularly at lower coolant temperatures, indicating greater film accumulation. Conversely, positions shielded from the spray exhibited minimal signal variation. Additionally, sensors mounted on the exhaust side showed faster recovery to baseline values, attributed to higher wall temperatures promoting quicker evaporation. In conclusion, the developed capacitive sensor demonstrated high sensitivity and reliability in detecting in-cylinder fuel films under realistic engine conditions. Its compact design and ease of integration make it a promising diagnostic tool for studying fuel film dynamics in production engines.
Kuboyama, Tatsuya, Nakajima, Takeru, Moriyoshi, Yasuo, Takayama, Satoshi, Nakabeppu, Osamu
A Study of Knocking Characteristics in a Hydrogen SI Engine under High Compression Ratio2025-32-006311/3/2025
This study investigated the knocking characteristics of a hydrogen spark ignition engine for the purpose of increasing efficiency and expanding the operating range. In recent years, research focused on carbon neutrality has been vigorously conducted, and hydrogen has attracted attention as a next-generation fuel for internal combustion engines (ICEs). The combustion characteristics of hydrogen are vastly from those of existing gasoline. It is essential to have a sufficient understanding of the combustion characteristics of hydrogen in order to develop next-generation ICEs designed to operate on hydrogen fuel. There are especially many aspects of the knocking mechanisms of hydrogen that are unclear. Consequently, those characteristics and mechanisms must be clarified for the purpose of expanding the operating range of hydrogen engines and enhancing their efficiency. In this study, experiments were conducted using a single-cylinder hydrogen engine that was operated at a high compression ratio of 17:1. High-intensity knocking was observed while operating the engine under various ignition timings and equivalence ratios. The knocking intensity and knocking mode characteristics were examined based on the observed knocking data.
Ishihara, Hiromasa, Kishibata, Shunsuke, Miyake, Shota, Iida, Tomoya, Kuwabara, Kenta, Yoshihara, Shintaro, Miyamoto, Sekai, Iijima, Akira
Effect of In-Cylinder Hydrogen Mixture Formation on Hydrogen Combustion2025-32-006511/3/2025
Global efforts to mitigate climate change include ambitious long-term strategies by countries to achieve net-zero greenhouse gas emissions by 2050. The automotive sector is exploring carbon-free powertrains, with hydrogen emerging as a key technology. Its zero-emission potential positions it for widespread adoption in power generation, transportation, and industry. Hydrogen engines, particularly direct injection engines offering high power and efficiency, are gaining traction due to their adaptability using existing engine components. However, in a hydrogen direct injection engine, achieving proper mixing of hydrogen and air in the cylinder is challenging, making in-cylinder mixture formation a crucial factor for ensuring stable combustion. To predict hydrogen mixture formation in the cylinder, we conducted a Schlieren visualization experiment of the hydrogen jet. Based on the results, a detailed hydrogen jet model for the direct injection injector was developed. This model was then integrated into the in-cylinder analysis, allowing an investigation into the impact of injection timing on hydrogen combustion. Furthermore, hydrogen combustion experiments were carried out using a single-cylinder hydrogen direct injection engine, and the accuracy of the in-cylinder analysis results was validated.
Hisano, Atsushi, Saitou, Masahito, Sakurai, Yota, Ichi, Satoaki
Advanced 3D Simulations of a Four-Stroke High-Performance Engine Valvetrain for the Analysis of the Mechanical Stresses and Energy Losses2025-32-001011/3/2025
Enhancing the performance of naturally aspirated 4-stroke engines relies heavily on improving trapping efficiency, increasing maximum engine speed, and reducing friction losses. In this regard, the valvetrain plays a critical role. Achieving high volumetric efficiency at higher engine speeds necessitates very steep valve opening and closing ramps, making this aspect pivotal in the design process. At high engine speeds, significant dynamic phenomena arise, including valve float during the lift phase and valve bounce during the closing phase. These effects not only induce substantial modifications to the valve lift curve but also increase the mechanical stress on critical components such as the valve and the rocker arm, thereby elevating the risk of failure. Moreover, the timing system substantially contributes to overall engine losses due to frictional energy dissipation, which results from the numerous interactions between moving components. The present work aims to develop a numerical model of the intake valvetrain of a high performance 4 stroke, single-cylinder engine, using the advanced 3D solver Comsol Multiphysics to accurately evaluate the stresses and deformations affecting each part. The simulation model includes camshaft, bearing, finger followers and the valves assembly (which includes valve, spring, retainer, and valve seat). Once the model was validated through comparison with experimental valve lift measurement, the interaction forces between the various components and the resulting mechanical stresses were analyzed. Subsequently, an investigation was conducted into the mechanisms responsible for the emergence of dynamic effects. Two different solutions were then tested in order to mitigate them. The use of the simulation software enabled a straightforward modification to be made to the material of the finger-follower, which was replaced with a lighter alternative in order to reduce the reciprocating masses. As a second solution, an alternative cam profile was designed, maintaining the same lift trend. This second approach resulted in a significant reduction of the dynamic effects acting on the valve during the closing phase, completely eliminating valve bounce. Furthermore, it enabled a substantial decrease in the mechanical stresses experienced by components such as the finger-follower and the valve-seat.
Tarchiani, Marco, Pizzicori, Alessio, Raspanti, Sandro, Romani, Luca, Meli, Enrico, Ferrara, Giovanni, Trassi, Paolo
Design, Optimization and Calibration of a Single-Cylinder, Motorcycle Engine for Integration into a Novel Formula SAE Electric Hybrid Powertrain2025-32-004511/3/2025
The Formula SAE competitions often drive changes in the automotive research field by developing, implementing and emphasizing new technologies for both on-road and on-track applications and by training future engineers, mechanics, logistics and administrative personnel. In this work, the adaptation of a motorcycle, single-cylinder engine for the installation in an electric hybrid car for Formula SAE races is described, focusing on the design of intake and exhaust parts and on the development of the fully open-access Engine Control Unit (ECU) code. In the first part of the work, the 1-D model of the engine is developed and used to design the intake and the exhaust parts needed to make the Formula Student car rules compliant. In particular, the intake manifold and the intake ducts have been designed with the assistance of the engine model to optimize the engine response under transient conditions and to maximize the power. On the other hand, the exhaust line was designed to increase the performance ensuring that it was compatible with the noise regulations imposed by the competition. In the second part of the paper, the experimental activity for the development and calibration of the ECU control strategies is described. The authors highlight how the 1-D engine model helps to reduce the time and cost of the experimental campaign, reducing the number of components that have to be tested. Moreover, the main results of the calibration process are summarized in the last part of the work and the final installation of the engine in the Formula SAE car is shown.
Brusa, Alessandro, Fabbri, Pietro, Shethia, Fenil, Bassani, Davide, Petrone, Boris, Cavina, Nicolo
Approaches for Mechanical Development and Validation of Hydrogen Internal Combustion Engines2025-01-039810/7/2025
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 angle resolved measurement of friction force between piston, rings and liner. A baseline and three different liner honing variants were measured during hydrogen operation and were compared to a baseline measurement during gasoline operation. In parallel, the oil consumption was determined by balancing all carbon-containing components in the intake air and exhaust gas. This is only possible when using a carbon-free fuel, like hydrogen. In addition, the measured influences on the single-cylinder engine were validated on the multi-cylinder engine. The aim is to find solutions that are advantageous for hydrogen propulsion, both in tribological terms and in terms of the tendency for oil-induced combustion anomalies. The measurement results are a very good base to identify further potentials for optimization and can be used as input for simulation models. The overall approach also supports the implementation of digital twins for a targeted and effective mechanical development and validation of future hydrogen engines.
Plettenberg, Mirko, Gell, Johannes, Grabner, Peter, Gschiel, Kevin, Hick, Hannes
Toward Sustainable Heavy-Duty Transport: Evaluating Charge Dilution and Advanced Corona Ignition System Effects on SI Natural Gas Engine Efficiency and Combustion Characteristics2025-24-00249/7/2025
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 Design2025-24-00089/7/2025
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
ML-based Identification of Lactones for Blend Studies and Combustion Performance in a Spark-Ignition CFR Engine2025-24-00719/7/2025
The identification of sustainable fuels that exhibit optimal physico-chemical properties, can be synthesized from widely available feed-stocks, enable cost-effective large-scale production, and integrate seamlessly with existing infrastructure is essential for reducing global carbon emissions. Given their high energy density, efficient handling, and versatility across applications, renewable liquid fuels remain a critical component of even the most ambitious energy transition scenarios. Lactones, cyclic esters derived from the esterification of hydroxycarboxylic acids, feature a ring structure incorporating both a carbonyl group (C=O) and an ether oxygen (O). Variations in ring size and carbon chain length significantly influence their physicochemical properties, which in turn affect their performance in internal combustion engines. According to predictive models based on artificial neural networks, valerolactone, hexalactone, and heptalactone isomers show promise as fuels in spark-ignition engines due to their high octane (RON and MON) values. In this work, a novel blending study of three lactones was performed to understand miscibility with iso-octane and certification gasoline and blending limitations. A blending limitation for one of the lactones was discovered and a single blend fraction of 30% lactone balanced with certification gas was tested in a spark ignition engine for the three lactones. An equivalence ratio sweep was performed for each fueling blend tested and no reduction in IMEPn and net fuel conversion efficiency was observed by displacing certification gasoline with renewable fuel.
Sirna, Amanda, Loprete, Jason, Ristow Hadlich, Rodrigo, Assanis, Dimitris, Patel, Rutvi, Mack, J. Hunter
A Novel Chemical Kinetics-Based Approach for Studying Feasibility and Optimise Retrofitting Strategies of Hydrogen CI Engines: Application to a Laboratory-Scale Single-Cylinder Engine2025-24-00549/7/2025
The climate emergency has prompted countries to adopt strategies to limit the rise in global temperatures by promoting low-carbon technologies. In this context, hydrogen (H2) can be considered a viable solution, especially in road and marine transportation, where Compression Ignition (CI) internal combustion engines (ICEs) are widely used. Despite its potential to significantly reduce pollutant emissions compared to fossil fuels, hydrogen presents a major challenge for CI engines due to its high autoignition temperature (greater than diesel). To overcome this problem, a novel methodology is proposed to evaluate the feasibility of hydrogen retrofitting. Each engine operating point is simulated as an ideal zero-dimensional (0D) reactor into which a diesel-hydrogen-air mixture is introduced. A fully detailed kinetic mechanism is used to simulate the complex chemical interactions between the two fuels, as well as its significant effect on engine behaviour, obtaining accurate predictions of autoignition timing. Three distinct time-based criteria are introduced to assess whether autoignition occurs during the compression stroke, and if so, to identify the corresponding crank angle. This information guides the selection of an appropriate hydrogen retrofitting strategy. The proposed methodology is validated against experimental data from a 500 cm3 CI single-cylinder research engine (SCRE) operated at CNR-STEMS. Two dual-fuel test cases at 1500 and 2000 revolutions per minute (rpm) are simulated. The comparison of the numerical results with respect to the experimental data demonstrates a good prediction within a discrepancy of 7°. Finally, for the mentioned test cases, the numerical model is applied to a local subdomain for estimating the local mixture composition at which autoignition experimentally occurs.
Episcopo, Domenico, Rossetti, Salvatore, Mancaruso, Ezio, Saponaro, Gianmarco, Camporeale, Sergio, Laera, Davide
Methodology for the Study of Hydrogen Combustion in an Optical Spark Ignition Engine2025-24-00629/7/2025
The use of hydrogen as a fuel in internal combustion engines represents a promising alternative for reducing CO2 emissions. To optimize its efficiency and better understand the phenomena associated with its combustion, it is essential to have advanced visualization techniques for a better understanding of the processes involved. This paper presents the methodology used in the development of an optical engine for the study of hydrogen combustion, designed from a 454cc single-cylinder engine. The configuration of the optical system is described, which includes the use of high-speed cameras to capture the spark plug activation as well as the flame propagation in the combustion chamber. The engine has two optical accesses, one through the piston and one at the top of the cylinder that allows side viewing of the combustion chamber. In addition, the experimental procedure that alternates combustion cycles with motoring cycles, the determination of the air-hydrogen ratio with which the engine is operating, the analysis of the combustion process, and the image processing used are detailed. As a conclusion of the work, it can be said that an optical engine has been manufactured, and a test methodology has been developed for the study of the hydrogen combustion process in spark ignition internal combustion engines.
Pastor, Jose V., Novella, Ricardo, Tejada, Francisco J., Cáceres-Carías, José
Numerical and Experimental Investigation of a Pre-Chamber Igniter for Enhanced Low Load Stability in Internal Combustion Engines2025-24-00029/7/2025
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
Water Injection Effects on a Heavy-Duty Hydrogen Spark Ignition Engine2025-24-00509/7/2025
Hydrogen engines have gained interest recently, as they present a promising alternative for decarbonizing heavy-duty transport, aligning with carbon neutrality regulations. This study investigates the effects of inlet manifold water injection on a heavy-duty hydrogen-fueled spark ignition single-cylinder engine, focusing on moderating abnormal hydrogen combustion and its impact on performance, thermal efficiency, and exhaust emissions. Water injection has been identified as a potential solution to mitigate the challenges associated with hydrogen combustion, such as pre-ignition and knock, by reducing the reactivity of the mixture (lowering temperature and increasing the dilution). The lower reactivity of the mixture allows running richer lambdas or higher compression ratios without spontaneous preignition, mitigating boosting requirements for full load and transient performance. Experimental results demonstrate that water injection significantly improves engine performance, thermal efficiency, and exhaust emissions. By injecting water into the intake charge, the peak combustion temperature is lowered due to its cooling and dilution effect, leading to a reduction in nitrogen oxide (NOx) exhaust emissions. This also allows a better combustion phasing, because the preignition tendency is reduced, enhancing thermal efficiency and performance. Furthermore, the study explores the possibility of increasing the compression ratio using water injection, to investigate the potential in thermal efficiency. The research highlights water injection effectiveness in controlling hydrogen combustion, allowing the possibility to operate at higher loads, with more compression ratio and less boosting requirements. This paper shows the potential of water injection as a viable strategy to act as an enabler for highly efficient SI heavy duty hydrogen engines capable of high load engine operation and low exhaust emissions, which is critical for heavy-duty applications under real-world conditions.
Peñin Garcia, Alfonso Jose, Valls Claramunt, Carles, Rivas, Manuel, Birnstingl, Johannes, Wieser, Martin, Martin, Jaime, Novella, Ricardo
Ammonia Combustion with Ignition Improvement Measures in a High-Speed Marine Application2025-24-00259/7/2025
Ammonia (NH3) has gained significant attention as a zero-carbon fuel which is capable of supporting global decarbonization goals, especially in the maritime transportation and power generation sectors. Its hydrogen density, storage feasibility, established production methods, and transportation infrastructure are key benefits which contribute to its potential both as a hydrogen carrier and as a direct fuel. The study investigates the combustion characteristics and emission profiles of ammonia on a spark ignited 2.13L single cylinder engine with the goal of evaluating ammonia as a single fuel. This displacement is representative of the typical cylinder displacement of small to mid-size engines for marine applications on sportfishing boats and as auxiliary power units. Challenges to consider for ammonia combustion are its high ignition energy requirement and low laminar flame velocity. Several methods were employed to compensate for these properties such as increasing compression ratio, the use of a passive pre-chamber spark plugs, and the use of hydrogen in a dual fuel set-up. The experimental results demonstrate stable combustion of 100 % ammonia under homogenous stoichiometric condition. NOX emissions reach typical levels of SI engines, around 8 – 12 g/kWh. Meanwhile, a certain level of NH3 emissions are unavoidable and require a customized exhaust aftertreatment. Up to 45 % indicated efficiency have been reached. The evaluation of the combustion enhancement techniques shows clearly that the higher CR, the use of a pre-chamber spark plug as well as the addition of a small hydrogen share all significantly reduce the burn delay and speed up the combustion considerably. Moreover, the NH3/NOX ratio in the exhaust gas is directly affected by these techniques which have relevance for the operation of an SCR aftertreatment system.
Li, Zhengling, Lückerath, Moritz, Pischinger, Stefan, Boberic, Aleksandar, Franzke, Bjoern, Dhongde, Avnish, Jagodzinski, Bartosch, Burrows, John, Korkmaz, Metin
Modeling and Experimental Study on Spark-Ignition Engine Using Hydrogen–Methane–Blended Fuel2025-01-50568/22/2025
A combustion model of a hydrogen–methane–blended fuel for internal combustion engines is developed and validated. Mixed fuels include hydrogen–methane, octane–methanol, and octane–ethanol blends. To address the complex dependencies of laminar flame speed of hydrogen–methane–blended fuel on temperature, pressure, equivalence ratio, and exhaust gas recirculation (EGR) ratio, a machine learning–based model was constructed. Gaussian process interpolation and polynomial extrapolation were employed to create a comprehensive laminar flame speed map. Additionally, two flame-quenching models, wall quenching and turbulent flame stretching, were introduced to predict unburned hydrocarbons. NOx emissions were estimated using the extended Zel’dovich mechanism. The accuracy of these models was verified by comparing numerical simulations with experimental data from single-cylinder engine experiments. Results showed strong agreement for cylinder pressure, heat release rates, and emissions across various hydrogen ratios and engine operating conditions. Across all investigated cases, the model reproduced combustion duration (CA10–90) within ±2.2°CA, with an error ≤11%. Notably, the machine learning–based laminar flame speed model demonstrated high accuracy, even at elevated temperatures and pressures, without requiring additional parameter tuning for turbulence flame model. This study highlights the highly accurate modeling techniques for simulating the combustion of renewable hydrogen–methane blends. The results in this study will contribute to the development of more efficient, lower emission internal combustion engines, and support the transition to sustainable vehicle technology.
Hayashi, Shinji, Yamada, Toshiyuki, Omori, Yuya, Nakagawa, Kentaro, Tanaka, Kotaro
Ethanol Fuel as Enabler for High-Efficiency and Low-Soot Combustion in Dual-Fuel and Blend Modes03-18-04-00287/16/2025
Global climate initiatives and government regulations are driving the demand for zero-carbon tailpipe emission vehicles. To ensure a sustainable transition, rapid action strategies are essential. In this context, renewable fuels can reduce lifecycle CO2 emissions and enable low-soot and NOx emissions. This study examines the effects of renewable ethanol in dual-fuel (DF) and blend fueling modes in a compression ignition (CI) engine. The novelty of this research lies in comparing different combustion modes using the same engine test rig. The methodology was designed to evaluate the characteristics of various injection modes and identify the inherent features that define their application ranges. The investigation was conducted on a single-cylinder engine equipped with state-of-the-art combustion technology. The results indicate that the maximum allowable ethanol concentration is 30% in blend mode, due to blend stability and regulatory standards, and 70% in DF mode, due to combustion stability and emission concerns. DF mode produces higher THC and CO emissions compared to blend or conventional diesel combustion (CDC) modes. However, ethanol consistently reduces smoke formation across all engine test conditions and fueling modes. At ultra-low-NOx levels (0.5 g/kWh), smoke emissions remain below 0.5 FSN. At the highest ethanol fraction in DF mode (70%), smoke emissions decrease to very low levels (−0.1 FSN), with improvements in thermal efficiency and CO2 emissions. DF mode requires specific injection control strategies to mitigate THC and CO emissions. In blend mode, the highest ethanol fraction (30%) results in CO2 and soot reductions, with CO and THC emissions comparable to CDC.
Belgiorno, Giacomo, Ianniello, Roberto, Di Blasio, Gabriele
Variable Valve Actuation and Multiple Injections to Enhance the Gas Exchange of a Passive Pre-Chamber Igniter2025-01-03157/2/2025
Pre-chambers, in general, represent an established technology for combustion acceleration by increasing the available ignition energy. Realizing rapid fuel conversion facilitates mixture dilution extension with satisfying combustion stability. More importantly, knock-induced spark retarding can be circumvented, thus reducing emissions and increasing efficiency at high engine loads. Adapted valve actuation and split injections were investigated for this study to enhance the gas exchange of a passive pre-chamber igniter in a single-cylinder engine. The findings support the development of passive pre-chamber ignition systems operable over the whole engine map for passenger vehicles. There are two configurations of pre-chamber igniters: passive pre-chambers and scavenged pre-chambers. This study focuses on the passive design, incorporating an additional small volume around the spark plug into the cylinder head. Hot jets exit this volume after the ignition onset through several orifices. These jets ignite the mixture in the main chamber, surpassing the ignition energy delivered by a spark plug. However, the major challenge for such igniters is the replacement of the residual gases during engine gas exchange. The combustion products of the previous working cycle need to be replaced by a fresh air-fuel mixture to facilitate the subsequent ignition. Controlling the pre-chamber gas exchange is decisive for series applications. The geometrical design of the pre-chamber influences its gas exchange. However, additional measures that are adaptable during engine operation must be identified to ensure stable engine operation. For this study, the adaptation of the intake valve actuation was investigated, and the cyclic variation was successfully reduced. Splitting the fuel injection into two separate events further enhanced combustion stability. Comprehensive measurements of the exhaust gas composition underlined the effectiveness of the introduced parameters to enhance passive pre-chamber ignition. Furthermore, analysis of the pressure traces in the main and pre-chamber provides insight into pre-chamber gas exchange and combustion initiation.
Fellner, Felix, Härtl, Martin, Jaensch, Malte
Effect of Gasoline Component on Fuel Economy of WLTC Drive with EGR and Lean Combustion2025-01-03057/2/2025
It is becoming increasingly clear that research into alternative fuels, including drop-in fuels, is essential for the continued survival of the internal combustion engine. In this study, the authors have evaluated olefinic and oxygenated fuels as drop-in fuels using a single-cylinder engine and considering fuel characteristic parameters. The authors have assessed thermal efficiency by adding EGR or excess air from zero to the maximum value that allows stable combustion. Next, we attempted to predict fuel efficiency for four types of passenger cars (Japanese small K-car N/A, K-car T/C, Series HV, and Power-split HV) by changing the fuels. We created a model to estimate fuel efficiency during WLTC driving. The results indicated that fuel economy could potentially be improved by adding an olefin fuel that burns stably even with a large amount of EGR or air and an oxygen fuel whose octane number increases. It was observed that the fuel economy improvement rate was particularly notable for Series-Hybrid Vehicle (HV) with operating under specific load and engine speed conditions.
Moriyoshi, Yasuo, Xu, Fuguo, Wang, Zhiyuan, Tanaka, Kotaro, Kuboyama, Tatsuya
Combustion and Emission Characteristics of Marine Ammonia-Diesel Dual Fuel Engine with Micro-Pilot Injector Change2025-01-02356/16/2025
Recently, as regulations on greenhouse gas emissions have become stricter, driven by global warming, there is increasing interest in engines utilizing environmentally friendly fuels. In this context, ammonia is attracting attention as a potential alternative to fossil fuels in the future. However, due to its distinct fuel properties compared to conventional fuels, research is being conducted on utilizing diesel as an ignition source for ammonia. In this study, the effects of diesel injector fuel flow rate, and micro-pilot (MP) diesel injection timing on combustion and exhaust emission characteristics were analyzed in a single cylinder 12L marine ammonia-diesel dual-fuel engine. Two types of diesel micro-pilot injectors were tested. The first one was high flow rate micro-pilot injector (HMPI) and the second one was low flow rate micro-pilot injector (LMPI). HMPI injector had 66% more number of fuel injector nozzle hole and 250% larger fuel flow rate. Therefore, HMPI injector could distribute diesel more widely within the combustion chamber in a short injection duration, which led to advantages such as an increased ratio of premixed combustion in diesel, improved oxygen utilization in the combustion cylinder, and enhanced ignitability of ammonia. To maintain a constant energy ratio between ammonia and diesel under steady engine load conditions, the injection durations were adjusted, and MP diesel injection timing was varied in increments of 5 crank angle degrees (CAD) to evaluate performance and emission characteristics. The experimental results showed that HMPI demonstrated higher thermal efficiency and lower unburned NH3 and N2O emission levels compared to LMPI. HMPI also showed improved overall performances under advanced MP diesel injection timing, however, performance of LMPI was also improved under the same conditions due to reduced interference between ammonia and MP diesel injection spray compared to the conditions under delayed MP diesel injection timing.
Jang, Ilpum, Park, Cheolwoong, Kim, Minki, Park, Chansoo, Kim, Yongrae, Park, Gyeongtae, Lee, Jeongwoo
Thermal Efficiency Improvement and Emission Reduction of Methanol Spark Ignition Engine Using Lean-Burn Strategy2025-01-02246/16/2025
Methanol is a promising fuel for achieving carbon neutrality in the transportation sector, particularly for internal combustion engine vehicles. With its high-Octane number, methanol enables higher thermal efficiency compared to gasoline engines. Additionally, its wide flammability range allows stable engine operation under lean burn conditions at low to mid-load levels. These characteristics make methanol well-suited for lean-burn strategies, which reduce pumping losses and enhance thermal efficiency. However, there remains a lack of studies on the influence of injection timing under different lean conditions, particularly in a wall-guided spark ignition engine. Wall-guided systems use the chamber wall or piston surface to redirect and stratify the fuel-air mixture near the spark plug at the time of ignition. The combustion performance of lean-burn engines in highly sensitive to variations in injection and excess air ratio. In this study, experiments were conducted on a single-cylinder engine to examine the combustion and emission characteristics under varying excess air ratios and the injection timings. At an SOI of -180 CAD aTDC, a thermal efficiency of 47.5% was achieved when the excess air ratio was increased. This corresponds to a 5.62% improvement in efficiency compared to the condition with excess air ratio (λ) 1.2 condition, representing the largest increase among all tested conditions. Due to high thermal efficiency, high vaporization heat of methanol, and low combustion temperature of lean conditions, nitrogen oxides emission decreased from 10.24 g/kWh to 2.23 g/kWh. However, corrected hydrocarbon emission increased from 3.07 g/kWh to 6.98 g/kWh under SOI -120 CAD aTDC condition, leading to the decline in combustion efficiency.
Lee, Seungwon, Kim, Hyunsoo, Hwang, Joonsik, Bae, Choongsik
Analysis of Combustion Characteristics of a Small 2-Stroke Opposed Piston Engine Using an Optically Accessible Engine and Numerical Analysis2025-01-02236/16/2025
As global warming becomes more serious, decarbonization of internal combustion engines, which emit a large amount of carbon dioxide, is being promoted. It is predicted that many vehicles will still be equipped with engines in 2035, and a variety of powertrains will be required in the future. Therefore, we focused on the opposed-piston engine as an internal combustion engine specialized for power generation applications. The opposed-piston engine is characterized by its light weight due to the absence of a cylinder head, low S/V ratio due to the ultra-long stroke, reduced cooling loss due to the long stroke, and reduced vibration due to the offsetting of the reciprocating inertial forces of the left and right pistons. We believe that the engine for power generation can achieve the required high efficiency operation and vibration reduction. Therefore, in this study, combustion analysis of a two-stroke opposed-piston engine with features of low vibration, high efficiency, and high output was conducted using numerical analysis to solve the vibration problem, which is a demerit of engines for power generation, and to further improve thermal efficiency. In this study, a prototype opposed-piston engine with a displacement of 126.6 [cc] was built and used as an experimental device, but it is difficult to visualize the inside of a cylinder of an opposed-piston engine. Therefore, an experiment was conducted using a 63.3[cc] an optically accessible single-cylinder engine with the same bore and half the displacement and stroke, and the results were compared with the numerical analysis results of the an optically accessible single-cylinder engine, and the validity of the numerical analysis was confirmed. Therefore, we considered that the combustion analysis of an opposed-piston engine was also valid, and we conducted a combustion analysis of an opposed-piston engine using CONVERGE.
Yamazaki, Yoshiaki, Watanabe, Sou, Okawara, Ikumi, Otaki, Yusuke, Liu, Jinru, Iijima, Akira
Improvement of Lean Burn Characteristics with Ozone Addition in a Diesel Micro-pilot Natural Gas Engine2024-32-01044/18/2025
Ozone (O3) was introduced into the intake air in a natural gas fueled engine ignited by micro-pilot of diesel fuel, to utilize the reactive O-radicals decomposed from the O3 for the promotion of the combustion and for improvements in the thermal efficiency and exhaust emissions. Experiments were carried out in a single cylinder engine to elucidate the effects of the ozone addition under the lean burn conditions. A supercharger was employed to increase the intake air amount and vary the equivalence ratio of natural gas. The experimental results showed that the O3 addition has a limited effect on the ignition of the diesel fuel injected near top dead center, while the heat release during the flame propagation in the natural gas/air mixture was increased at the lower equivalence ratio of natural gas. Further the ignition of natural gas was promoted, resulting in the increase of the combustion efficiency and the degree of constant volume heat release. The cooling loss and the NOx emissions decreased due to the leaner burn achieved by the supercharging. Overall, the indicated thermal efficiency and the exhaust emissions can be improved by the supercharging combined with the O3 addition.
Kobashi, Yoshimitsu, Miyata, Shoki, Kawahara, Nobuyuki, Inagaki, Ryuya
Dynamic Analysis of Intake and Exhaust Valve Motion in a High-Performance four Stroke Engine. Part 2 - Development of a Numerical Model for the Simulation of the Valvetrain2024-32-00844/18/2025
The intake and exhaust valve motion have, as known, a pivotal role in determining engine operation and performances. When dealing with high specific power engines, especially at high rpm, the dynamic behavior of the valve can differ from the kinematic one defined during the design phase. This is related to the high acceleration and forces to which the valve and the other components of the valvetrain system are subjected. In particular, the valve can detach from the cam profile at the end of the opening stroke, and it can show a bouncing behavior during the closing stroke. In addition, all the elements of the valvetrain system are not infinitely rigid and aspects such as the timing chain elongation, the camshaft torsion and the valve stem compression can determine a change in phase with respect to the kinematic one. Since the high complexity level of valvetrains, advanced numerical simulations are mandatory to deeply analyze the behavior of the whole mechanism and each subsystem. The objective of this study is to develop a one-dimensional model to simulate the valvetrain system of a four-stroke single cylinder engine for racing application. The engine is provided with four valves, and two camshafts. The model is capable of accurately reproducing and predicting the actual motion of valves, including phenomena like valve float and bouncing behaviors at high RPMs. The GT-suite© modeling environment, developed by Gamma Technologies, is utilized for this purpose. The work focuses on modeling various elements of the valvetrain system and provides a thorough account of model calibration using experimental data, including a sensitivity analysis of key model parameters. Modeled elements include the valve itself, the camshaft, chain gears, timing chain, and sliders. By evaluating real valvetrain behavior, the study enables comparisons between different components, such as various camshaft profiles or valve springs, to ensure the desired valve motion within the designated operating range.
Tarchiani, Marco, Romani, Luca, Raspanti, Sandro, Bosi, Lorenzo, Ferrara, Giovanni, Trassi, Paolo, Fiaschi, Jacopo
Techniques and Analysis Methods Used in Development of 13.4kW Horizontal Water-Cooled Diesel Engine2024-32-01164/18/2025
Horizontal water-cooled diesel engines are single-cylinder engines equipped with all the necessary components for operation such as a fuel tank and a radiator. Due to their versatility, there are used in a wide range of applications in Asia, Africa, South America, etc. It is necessary to comply with strengthened emissions regulations year by year in countries where environmental awareness is increasing such as China, India, etc. We have developed a new compact and high-power 13.4kW(18HP) engine which meets these needs. We realized a high-power density by using our unique expertise to maintain an engine size and increase a displacement. In addition, by optimizing a layout of crankcase ribs through structural analysis, we have achieved a maximum bore and “Reduction of the weight of the crankcase and lubricating oil consumption (LOC), and reduction of friction with narrow-width low-tangential load piston rings”. Furthermore, by designing an intake port using 3D CFD, we have optimized a swirl ratio and improved a flow coefficient to improve a fuel efficiency. About conforming to emissions regulations, we utilized 3D CFD to select an optimized nozzle specification and 1D CAE to optimize internal EGR. As a result, we have showed a potential to conform to “Limits and measurement methods for exhaust pollutants from diesel engines of non-road mobile machinery (CHINA IV)” for the new engine with a mechanical injection system. This paper introduces the technology to achieve a high-power density, a low fuel consumption, a high durability and a compliance with emissions regulations simultaneously.
Shiomi, Kenta, Hosoya, Ryosuke, Komai, Yoshinobu, Takashima, Yusuke, Kitamura, Takahiro, Fujiwara, Tsukasa, Suematsu, Kosuke
Experimental Study of Glow Plug Assisted Methanol Compression Ignition2025-01-84124/1/2025
Methanol can be produced renewably and used in compression ignition (CI) engines as a replacement for fossil diesel. However, methanol is a low cetane fuel, creating challenges in achieving stable operation, particularly at low load. One potential solution is through surface ignition via a glow plug. In this work, experiments were conducted on a methanol-fueled 2.1 L single cylinder engine instrumented with a glow plug. The engine was designed for alcohol combustion with an elevated compression ratio (26:1) and a narrow injector umbrella angle (120 degrees) compared to standard diesel compression ignition hardware. As such, no plume was directly intercepted by the glow plug. A representative low load case of two conventional mixing controlled compression ignition (MCCI) strategies (single injection and pilot-main) and three kinetically controlled advanced CI strategies (homogenous charge compression ignition, split injection, partially premixed combustion) were tested with and without the glow plug active. It was found that the glow plug had no significant impact on either MCCI strategy because no plume was directly intercepted by the glow plug. In the advanced combustion strategies, the glow plug advanced combustion phasing by several degrees, due to an apparent combination of charge heating and small amounts of exothermic reactions from fuel located near the glow plug during the compression stroke. When the charge was heavily stratified, it was hypothesized that flames could propagate from the glow plug and the start of combustion could advance substantially. However, this significantly decreased low load stability as cyclic variability in the local conditions near the glow plug resulted in high cyclic variability in flame propagation and subsequent autoignition of the charge. This work highlights the potential incompatibility between narrow angled injectors designed for alcohol CI and glow plugs, as well as the ineffectiveness of glow plugs in alcohol fueled advanced combustion strategies.
Gainey, Brian, Svensson, Magnus, Verhelst, Sebastian, Tuner, Martin
Nitrogen Oxides Reduction Potential Via Water Direct Injection in a Single-Cylinder Hydrogen-Fueled Direct Injection Spark Ignition Engine2025-01-84274/1/2025
In hydrogen-fueled internal combustion engine (H2ICE), there are some ways to reduce nitrogen oxides (NOx) emissions. Using the wide flammability range of hydrogen, such as conducting lean combustion to reduce nitrogen oxides and employing exhaust gas recirculation (EGR), have been adopted. However, challenges exist in terms of load expansion, and due to the absence of high heat capacity of carbon dioxides in the exhaust, EGR also struggles to exhibit significant effects. In such a scenario, there is growing interest in injecting water into the H2ICE as an alternative to augment the EGR effect. In this study, the spark ignition (SI) single-cylinder engine equipped with two direct injectors was used to evaluate the hydrogen and the water dual direct injection combustion system. This system involved the direct injection of hydrogen using a wall-guided gasoline direct injector and the direct injection of water into the combustion chamber using a diesel injector. This approach utilizes the vaporized water not only to act as EGR but also to aid in combustion chamber cooling through the latent heat of vaporization of water, thereby reducing the impact on volumetric efficiency. The main variables were injection timing and the amount of water. Engine speed was fixed at 1,500 rpm and there were two excess air ratio conditions at 2.2 and 1.5(richest limit condition). The result emphasized that the maximum NOx reduction potential was 80% when the water amount was 15.8 mg/str under the excess air ratio of 2.2 due to its latent heat and dilution effects. In addition, this value correspondence to EGR 27.4% so that water direct injection was effective to reduce NOx emissions.
Kim, Kiyeon, Lee, Seungil, Kim, Seungjae, Lee, Seunghyun, Min, Kyoungdoug, Oh, Sechul, Son, Jongyoon, Lee, Jeongwoo
Experimental and Numerical Investigation of Different Dilution Techniques in a High-Performance H2 - Fueled SI Engine2025-01-84244/1/2025
Nowadays, hydrogen (H2) is rising as a key solution to fuel internal combustion engines (ICE) since it allows carbon free combustion process. At the same time, ICE fueled with H2 can reach similar performance and driving experience of gasoline fueled ones. In stoichiometric conditions, hydrogen shows higher flame speed, lower ignition energy and lower quenching distance than gasoline. Mainly for these reasons, H2 combustion is characterized by a high risk of abnormal combustion (i.e. knock and pre-ignition), relevant NOx emissions and high heat losses. On the other hand, the wide flammability range and high combustion stability of H2 allow the use of different techniques to reduce combustion reactivity. This work presents a combined approach, experimental and numerical, to assess the benefits of three mixture dilution methods. The experimental campaign, in different operating conditions, was carried out on a production derived high specific power gasoline Single Cylinder Engine (SCE) retrofitted to H2 with Direct Injection (DI). Three different dilution techniques were tested: enleanment, cooled Exhaust Gas Recirculation (cEGR) and manifold Water Injection (WI). The impacts on combustion of the different strategies were analyzed in order to evaluate their effectiveness on engine thermal efficiency and NOx emissions. Enleanment has a relevant impact on the size of the turbocharger system, cEGR affects the engine total heat rejection, while WI requires dedicated injection system and tank. Therefore, each dilution strategy requires a dedicated hardware optimization. In this regard, a 1D-CFD simulation model of complete 6-cylinder engine was developed with the aim to assess the above-mentioned techniques in terms of fuel economy and heat rejection at low-medium loads.
Tonelli, Roberto, Medda, Massimo, Gullino, Fabrizio, Silvestri, Nicola, Zaffino, Francesco, Mariconti, Roberto, Rossi, Vincenzo
Impact of Oxygenated Fuel Components on Engine Performance and Particulate Emissions in Gasoline Blends2025-01-84464/1/2025
The challenges with electrification in the automotive industry have led to rethinking the decisions to ban internal combustion engines. Nonetheless, decarbonization of transportation remains a regulatory priority in many countries, irrespective of the energy source for automotive powertrains. Renewable oxygenated fuel components can help with the rapid decarbonization of gasoline fuels in the current fleet. Ethanol is one of the primary renewable components typically used for blending in gasoline primarily at 10% v/v but up to 20% v/v substitution which corresponds to 3.7 to 8.0% oxygen by mass. However, a range of oxygenates could be used instead of ethanol. This study aimed to determine if the engine could discriminate between different oxygenates in gasoline fuels blended at the same octane (RON) and oxygen levels. Oxygenates such as methyl-tert-butyl-ether (MTBE) and ethyl-tert-butyl-ether (ETBE) were considered in this study. Blends were made using a combination of n-heptane, iso-octane, toluene, and oxygenated components. Seven blends with a nominal RON of 98 +/-2 were evaluated in a single-cylinder engine. Four E10 equivalent and three E20 equivalent fuel blends were studied. The engine was operated at a range of test conditions from throttled, low-load points to boosted, high-load points that required knock retard. The results indicated that all blends had minimal differences in engine performance in terms of knocking behavior, spark timing, burn duration, fuel flow, and injection duration which could all be compensated by the engine control unit (ECU). Particulate matter emissions (AVL micro soot sensor, PN10, PN23) were also evaluated at the test conditions. While the fuels had lower PM-generating components compared to commercial fuels, we could demonstrate that the PM emissions largely correlated with the particulate matter index (PMI) (or the toluene content) of the fuels.
Kalaskar, Vickey, Mitchell, Robert, Pourreau, Daniel
Enhancing Dual Fuel Combustion Simulation: A Novel Geometric Approach for Accurate Flame Entrainment Estimation2025-01-83664/1/2025
Maritime transportation plays a vital role in the economy and is one of the most energy-efficient modes of transportation. However, it is a growing source of greenhouse gas emissions. A potential solution to lower carbon emissions from maritime transport is to use renewable fuels in marine engines. Hydrogen or methanol can serve as the primary energy source in internal combustion (IC) engines. However, their high autoignition temperatures require an external ignition source to start combustion in compression ignition (CI) engines. The Dual Fuel (DF) approach offers an effective method for incorporating these fuels. To accurately simulate dual fuel combustion, certain parameters need to be carefully addressed. One crucial parameter to investigate is estimating the flame entrainment area, as it directly affects the mass burning rate. In this work, a novel geometric approach is developed to estimate the evolution of the flame entrainment area. This model is integrated into a multi-zone dual fuel combustion model in GT-Power and evaluated against experimental data from a single-cylinder engine (SCE) running on methanol in dual fuel mode, specifically 25 different cases with a bore size of 240 mm (SCE1) and 25 cases with a bore size of 256 mm (SCE2). The results show that using the new flame area model reduces the root mean square error (RMSE) in predicting combustion phasing (CA90) from about 10 crank angle degrees (CAD) to approximately 3.5 CAD for SCE1 and from 18 CAD to 8 CAD for SCE2. Additionally, there is a reduction in RMSE for predicting the indicated mean effective pressure (IMEP), from 2.3 bar to 1.3 bar for SCE1 and from 1.5 bar to 1.0 bar for SCE2. Significant improvements are also observed in the heat release rate curve, specifically in the tail of combustion.
Parsa, Somayeh, Daenens, Arthur, Verschaeren, Roel, Dierickx, Jeroen, Verhelst, Sebastian
10 % Fuel Economy Benefit at Part Load and up to 33 % at Idle for a Diesel Engine via Reducing Friction. Testing the Rotating Liner Engine and an Identical Baseline Under Load2025-01-83904/1/2025
The Rotating Liner Engine (RLE) is a design concept where the cylinder liner of a heavy-duty Diesel engine rotates at about 2-4 m/s surface speed to eliminate the piston ring and skirt boundary friction near the top and bottom dead center. Two single cylinder engines are prepared using the Cummins 4BT 3.9 platform, one is RLE, the other is baseline (BSL), i.e. conventional. In 2022, we published the test results of the RLE under load, but we lacked detail test data for the baseline. In this new set of experiments, we compare the RLE performance at idle and under load of up to about 7 bar IMEP (indicated mean effective pressure) to the baseline under similar conditions. It has been proven that the elimination of metallic contact between the compression rings and cylinder wall takes place with a liner speed of 1.5-2.3 m/s surface speed (283-426 rpm for the 102 mm bore) for the 850-1280 rpm crankshaft speed. The RLE FMEP is substantially reduced under load, which is a trend opposite to standard engines. The total reduction of FMEP for idle and medium load is measured to be 0.4 and 0.8 bar respectively. When the above results are applied to complete rather than single cylinder engine application, the combined fuel efficiency benefit is approximated to a fuel consumption reduction of 33 % at idle and up to 10 % for medium loads and speeds. Minimization of cylinder and piston ring wear is expected. One significant observation from the research is that the piston rings and skirt boundary friction is a dominating factor in the friction losses of the modern diesel engine. We have not yet operated the two engines under forced air induction, but we expect the RLE benefit to be approximately double the 0.8 bar measured benefit of the naturally aspirated engines. Extrapolating the experimental results to a 20 bar BMEP bring fuel economy improvement to over 7 %
Dardalis, Dimitrios, Hall, Matthew, Riley, Sebastian, Basu, Amiyo, Matthews, Ron
Combustion of Hydrated Ethanol and Gasoline RON95 Ultra-High Pressure Direct Injection in Optical Access SI Engine2024-36-015212/20/2024
High and ultra-high pressure direct injection (UHPDI) can enhance efficiency gains with flex-fuel engines operating on ethanol, gasoline, or their mixtures. This application aims to increase the engine’s compression ratio (CR), which uses low CR for gasoline due to the knocking phenomenon. This type of technology, involving injection pressures above 1000 bar, permits late fuel injection during the compression phase, preventing auto-ignition and allowing for higher compression ratios. UHPDI generates a highly turbulent spray with significant momentum, improving air-fuel mix preparation, and combustion, resulting in even greater benefits while minimizing particulate matter emissions. This study aims to develop ultra-high-pressure injection systems using gasoline RON95 and hydrated ethanol in a single-cylinder engine with optical access. Experimental tests will be conducted in an optically accessible spark ignition research engine, employing thermodynamic, optical, and emission results. In the present work, the spark plug was placed in the lateral, so the ignition and part of the flame propagate close to the cylinder wall, and it will exchange with greater heat to the wall than the flame portions that propagate towards the central region of the chamber. Therefore, the flame front propagates at different speeds; causing stretching and wrinkling that can lead to instabilities and cyclic variability. To address this issue, this work presents experimental results that, through the images post-processing of flames under a SOI (start of injection) sweep strategy in the compression phase to closer of the spark ignition, associating the non-uniform propagation velocity of the flame with the cyclic variability. The fuel impingement on the wall was critical in this scenario, which led to higher soot concentrations and diffusive flames for gasoline. It was found that the injection close to the spark plug enhances the heat release, and combustion stability, decreasing soot emissions. Total unburned hydrocarbons (THC), Nitrous oxides (NOx), aldehydes, and soot emissions decreased for end of injection events closer to the spark ignition. This trend opposes the increase observed in CO emissions.
Malheiro de Oliveira, Enrico R., Mendoza, Alexander Penaranda, Martelli, Andre Luiz, Dias, Fábio J., Weissinger, Frederico F., dos Santos, Leila Ribeiro, Lacava, Pedro Teixeira
Prediction of WLTC Mode Drive Fuel Consumption for Vehicles Running on Blended Gasoline2024-01-429111/5/2024
It is becoming increasingly clear that research into alternative fuels, including drop-in fuels, is essential for the continued survival of the internal combustion engine. In this study, the authors have evaluated olefinic and oxygenated fuels as drop-in fuels using a single-cylinder engine and considering fuel characteristic parameters. The authors have assessed thermal efficiency by adding the EGR amount from 0 to the maximum value that allows stable combustion at the theoretical air-fuel ratio. Next, we attempted to predict fuel efficiency for three types of passenger cars (Japanese small K-car N/A, K-car T/C, and Series-HV) by changing the fuels. We created a model in OpenModelica to estimate fuel efficiency during WLTC driving. The results indicated that fuel economy could potentially be improved by adding an olefin fuel that burns stably even with a large amount of EGR and an oxygen fuel whose octane number increases. It was observed that the fuel economy improvement rate was particularly notable for Series-Hybrid Vehicle (HV) with operating under specific load and engine speed conditions.
Moriyoshi, Yasuo, Kuboyama, Tatsuya, Kawakami, Sota, Wang, Zhiyuan
Experimental Investigation on Combustion Strategy of Light Duty GCI Fueled High Reactivity Gasoline Fuel2024-01-428211/5/2024
Diesel engines are largely used as power units with high fuel efficiency. Conversely, they have an adverse impact on the environment and human health as they emit high NOx and particulate matter emissions. As more stringent regulations for emissions are introduced, low temperature combustion strategy such as Gasoline Compression Ignition evolved and demonstrated the potential to reduce the particulate matter and NOx emissions by operating engines under a Partially Premixed Combustion mode. Therefore, a 0.55 mm single cylinder engine (Gasoline Direct Injection), was tested over range of engine loads with constant speed (1500 rpm) using RON80 without oxygenates. Different operating parameters such as injection, exhaust gas recirculation (EGR) etc. were used to control combustion phasing and mixture stratifications. At low loads, rebreathing of hot exhaust gas produced low levels of NOx and smoke emissions. It reduced NOx by 60% and smoke levels below 0.20 FSN when it is coupled with low levels of EGR. At medium to high loads, alternative injection strategies were explored to find proper combustion mode with very low NOx of 0.01 g/kwh and smoke of 0.01 FSN emissions while meeting combustion noise targets. Minimum ISFC was measured at 195 g/kwh at 13 bar IMEP.
Qahtani, Yasser Al, Sellnau, Mark, Yu, Xin
Powertrain NVH Optimization of Single Cylinder CI Engine2024-28-000110/17/2024
With increasing pursuit for comfort in mobility NVH characteristics are becoming more important than ever. Achieving a benchmark beating NVH behavior involves optimizing source, transfer paths as well as target location mechanical characteristics. In ICE vehicles, powertrain accounts for major source of noise and vibration. This work encompasses NVH refinement strategies for a single cylinder compression ignition engine. The work starts with setting target values for NVH characteristics based on competitive benchmark data analysis. A complete development strategy involving extensive testing and CAE correlation is presented here. Contribution analysis in component level for optimization of NVH behavior is carried out employing NVH testing in anechoic chamber supported by CAE simulations. This paper describes the later phases of the entire development process which are decisive for engine NVH; the combustion and mechanical development phase and the NVH development and refinement phase. In order optimize engine acoustical performance, experimental identification and localization of noise sources were performed at different speed and load. Correlation of noise to structural vibrations and resonances were established and design matured using simulation and proved with experimental validation to achieve the set targets. Deep down analysis of various powertrain components was done to reduce source noise and vibrations. CAE models were created for design optimizations which were validated using test results. Force analysis was performed, and balancer shaft was designed to reduced inertial forces causing vibration as net unbalanced forces are always a concern in single cylinder engines. Finally complete validation of the powertrain accommodating all the optimizations is done in semi anechoic testbench as well as in vehicle.
Kunde, Sagar, Thakur, Sunil, Wagh, Sachin, Bhangare, Amit, Prabhakar, Shantanu
Influence of Lube Oil and Fuel Additives on the Particulate Raw Emission Behavior of Gasoline Engines04-18-01-000410/3/2024
The aim of this work was to investigate the influence of different combinations of engine oil and oil additive as well as additivated and unadditivated fuel on particulate emissions in gasoline engines. To accomplish this, load, speed, and type of oil injection were varied on a single-cylinder engine, and the influence on particle number concentration and size distribution were evaluated. The tests were supplemented by an optical investigation of their in-cylinder soot formation. The investigation of fuel additives showed no significant differences compared to the reference fuel without additives. However, in the case of oil additives, detergents led to a significant increase in the number of particles in the <20 nm range. This effect occurred when used as both a single additive and a component in the standard engine oil. While viscosity improvers also lead to a measurable, but less pronounced, increase in the particle number concentration, no significant influence can be determined for any other oil additives. The influence of the additive is independent of the type of oil introduction by injection into the intake manifold or direct injection of a premixed oil/fuel mixture.
Böhmeke, Christian, Heinz, Lukas, Wagner, Uwe, Koch, Thomas
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