Browse Topic: Ignition systems

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Effect of E20 Fuel on Small Commercial Vehicle Powered of Twin Cylinder Gasoline engine2026-26-0565To be published on 01/16/2026
In alignment with its carbon reduction commitments, India is transitioning towards higher ethanol-blended fuels, with E20 set for nationwide implementation by 2025. Ethanol is a renewable, domestically sourced biofuel produced through fermentation of biomass such as sugarcane, corn. It possesses a higher octane rating and oxygen content compared to conventional gasoline, making it a favorable additive for improving engine performance and reducing emissions. This study investigates the impact of E20 fuel on performance parameters of a twin-cylinder MPFI gasoline engine. For deriving maximum benefits of increased Octane rating of E20, compression ratio increased. Experimental analysis was conducted to assess the changes in combustion behavior, brake specific fuel consumption (BSFC), torque output, engine out emissions and thermal efficiency when operating on E20 compared to baseline gasoline-E10. Results indicate that E20 enables more efficient combustion due to its higher laminar flame
Kulkarni, Deepak, Malekar, Hemant A, Kulkarni, Chaitanya, Thonge, Ravindra, Kanchan, Shubham
Technologies and Strategies for High Break Thermal Efficiency Gasoline Engine to Meet the Future CO2 Emission Targets in India2026-26-0072To be published on 01/16/2026
The Indian automobile industry is experiencing a significant shift, propelled by environmental necessities and national climate obligations set at the CoP26 summit, aiming for a 45% decrease in CO₂ emissions by 2030 and reaching carbon neutrality by 2070 [1]. Transportation continues to be a significant source of air pollution; consequently, India is enhancing its regulatory frameworks with BS VI Stage 2 regulations, CAFE Phase III norms set for 2027, and CAFE Phase IV by 2032 [2]. Furthermore, the transition from MIDC to WLTP driving cycle is meant to increase the accuracy of the efficiency and emissions assessments [2]. To comply to these upcoming regulations, the automotive industry is moving toward producing high efficiency engines in India. A naturally aspirated (NA) 1.5L, 4- cylinder inline gasoline engine was selected from Indian market for this study. Maximum Brake Thermal Efficiency (BTE) of this engine is around 35%. Assessment of new technologies were performed by
Emran, Ashraf, Jagodzinski, Bartosch, Garg, Shivam, Fischer, Marcus, Franzke, Bjoern
Comprehensive Validation Methodologies for Hydrogen IC Engines: Combustion Analysis and Performance Metrics2026-26-0256To be published on 01/16/2026
The validation of hydrogen-fuelled internal combustion engine (H2 ICE) is critical to assess its feasibility as sustainable transportation with zero carbon emissions. Validation of H2 ICE necessitates a specialized testing & analysis methodologies to achieve reliable test results. This study shows the adverse effects on engine performance due to barometric pressure variation, turbo compressor out temperature variation due to increase in ambient temperature. The analysis also shows experimental results of engine performance variation based on hydrogen gas quality. Charge air quality reduces due to presence of nitrogen and moisture content in hydrogen gas and has direct impact on combustion. Engine Performance variation also observed due to engine components detoriation like valve seat wear & spark plug gap expansion. This study emphasizes the significance of precise instrumentation of thermocouples across engine on cylinder head, intake manifold & exhaust manifold, to detect performance
Vasudevan, Sindhuja, J, Narayana Reddy, Bolar, Yogesh Ganesh, Pandey, Sunil, N, Harish, N R, Varatharaj, Karthikeyan, K, Kumar D, Kishore
Ammonia Combustion with Active Pre-Chamber Spark Plug - a CO2-free Combustion Process2025-01-0527To be published on 11/25/2025
As a zero carbon fuel, ammonia has the potential to completely defossilize combustion engines. Due to the inert nitrogen present in the molecule, ammonia is difficult to ignite or burn. Even if the ammonia can be successfully ignited, combustion will be very slow and there is a risk of flame quenching, i.e. the flame going out before the ammonia-air mixture has been almost completely converted. Both the difficult flammability and the slow combustion result in high ammonia slip, which should be avoided at all costs. The engine efficiency is also greatly reduced. Safe ignition and burn-through can be achieved by drastically increasing the ignition energy and/or using a reaction accelerator such as hydrogen. The planned paper will use detailed 1D and 3D CFD calculations to show how high the potential of ammonia combustion in an internal combustion engine is when an active pre-chamber is used as the ignition system. As a result of the flare jets penetrating into the main combustion chamber
Sens, Marc, von Roemer, Lorenz, Rieß, Michael, Fandakov, Alexander, Casal Kulzer, Andre
Multi-Objective Optimization of Oxyfuel Gas Engine Using Stochastic Engine Model and Detailed Chemistry2025-01-0529To be published on 11/25/2025
The energy transition initiatives in Germany’s renown coal mining region Lusatia have driven research into Power-to-X-to-Power (P2X2P) technologies, where synthetic fuel is produced from renewably sourced hydrogen and captured CO2, and converted to electricity and heat through oxyfuel combustion. This work investigates the multi-objective optimization of oxyfuel gas engine using stochastic engine model (SEM) and detailed chemistry. EGR rate, initial cylinder temperature and pressure, spark timing, piston bowl radius and depth are selected as design parameters to minimize the exhaust temperature at exhaust valve opening (EVO) and indicated specific fuel consumption (ISFC) corresponding to oxyfuel operation with different dry and wet exhaust gas recirculation (EGR) rates. The optimization problem is solved for a dry EGR and four wet EGR cases with various CO2 / H2O fractions, aiming to achieve comparable performance as in conventional natural gas / air operation, along with an energy
Asgarzade, Rufat, Franken, Tim, Mauss, Fabian
Investigation of Active Pre-Chamber Ignition on an Optically Accessible Ultra-Lean DI Hydrogen Engine2025-01-0524To be published on 11/25/2025
Hydrogen is a promising alternative to conventional fuels for decarbonizing the commercial vehicle sector due to its carbon-free nature. This study investigates the ignition and flame propagation characteristics of hydrogen in a 2-liter single-cylinder optical research engine representative of the commercial vehicle sector. The main objective was to enable high power density operation while minimizing NOx emissions. For that, ultra-lean combustion was employed to lower in-cylinder temperatures, addressing the challenge of NOx formation. To counteract delayed and unstable combustion under lean conditions, an active pre-chamber ignition system was implemented. It uses a gas-purged pre-chamber with separate hydrogen injection and spark plug ignition. Turbulent hot gas jets from the pre-chamber ignite the fresh mixture in the main combustion chamber, enabling faster and more stable ignition compared to conventional spark plugs. Additionally, the low volumetric energy density of hydrogen
Borken, Philipp, Bill, Daniel, Link, Lukas, Dinkelacker, Friedrich, Hansen, Hauke
Optimization of Injection Parameters for a Free-Piston Engine Equipped with Flat-Head Combustion Chamber2025-01-507511/11/2025
The free-piston engine represents a paradigm shift in internal combustion engine technology, with its unique structure promising efficiency gains. However, injection parameters are one of the core elements of free-piston engine performance. This study employs computational fluid dynamics analysis to optimize the spray cone angle and start of injection timing for a two-stroke dual-piston opposed free-piston engine equipped with a flat-head combustion chamber. A three-dimensional transient model incorporating dynamic adaptive mesh refinement was constructed by using CONVERGE 3.0 software. The results indicate that a spray cone angle of 25° achieves optimal fuel distribution, yielding a peak indicated thermal efficiency of 42.14% and an indicated mean effective pressure of 9.08 bar. Crucially, advancing the ignition timing to 215°CA improves mixture homogeneity but simultaneously increases peak cylinder temperatures and NOx. Conversely, delayed start of injection timings reduces NO
Xu, Zhaoping, Yang, Shenao, Liu, Liang
High-Tension Ignition CableJ2031_202511 (Current)11/06/2025
The specifications contained in this SAE Standard pertain to high-tension ignition cable used in road vehicle engine ignition systems.
Ignition Standards Committee
Development of a Combined Injection and Ignition Unit for a Gas Engine with Direct Hydrogen Injection Integrated into the Standard Spark Plug Access Hole2025-32-005911/03/2025
To achieve the desired fuel switch from natural gas to hydrogen in internal combustion engines for combined heat and power units, it is necessary to make some adjustments to the fuel supply system. External gas mixers increase the probability of backfiring when natural gas is replaced by hydrogen. In addition, the low density of hydrogen results in a loss of power. Therefore, direct gas injection is preferred when using hydrogen. A drawback of direct injection is the requirement of higher injection pressures to achieve the desired fuel mass and mixture homogeneity as well as the additional access to the combustion chamber for the direct gas injector in the cylinder head. This paper proposes an alternative approach that does not necessitate the implementation of a high-pressure direct injection system nor additional access to the combustion chamber via the cylinder head. A combined injection and ignition unit, called HydroFit, was developed which uses a sleeve inside the spark plug bore
Rischette, Nic, Holzberger, Sascha, Helms, Sven, Kettner, Maurice
Clarification of the Mechanism of Abnormal Combustion in Hydrogen Engines -Investigation of Abnormal Combustion Location by Visualization Measurement-2025-32-006411/03/2025
Hydrogen internal combustion engines present a promising path towards carbon neutrality, yet their development is challenged by abnormal combustion phenomena like backfire and pre-ignition. These phenomena limit engine torque and reduce component reliability. This study is aimed to elucidate the mechanisms behind these phenomena in hydrogen internal combustion engines. We utilized a multi-cylinder engine with optical access for direct high-speed imaging of in-cylinder processes to visualize backfire and pre-ignition. Initial analysis, combining visualization data with one-dimensional (1D) simulations, indicated that high temperatures of the ground electrode of the spark plug could be a key trigger factor for abnormal combustion. To investigate this hypothesis, the surface temperature of the ground electrode was measured under firing conditions using a two-color thermometry system. The measurements revealed that the electrode temperature exceeded the compressed gas temperature near Top
Muramatsu, Keiji, Tokuhara, Satoshi, Kadu, Pravin, Yoshimura, Kei, Nakama, Kenjiro
Analysis of Flame Propagation Characteristics in a Hydrogen Engine using an Optically Accessible Engine2025-32-006111/03/2025
This study focused on the effects of hydrogen on the flame propagation characteristics and combustion characteristics of a small spark-ignition engine. The combustion flame in the cylinder was observed using a side-valve engine that allowed optical access. The fundamental characteristics of hydrogen combustion were investigated based on combustion images photographed in the cylinder with a high-speed camera and measured cylinder pressure waveforms. Experiments were conducted under various ignition timings and equivalence ratios and comparisons were made with the characteristics of an existing hydrocarbon liquid fuel. The hydrogen flame was successfully photographed, although it has been regarded as being difficult to visualize, thus enabling calculation of the flame propagation speed. As a result, it was found that the flame propagation speed of hydrogen was much faster than that of the existing hydrocarbon fuel. On the other hand, it was difficult to photograph the hydrogen flame
Arai, Yuto, Ueno, Takamori, Suda, Ryosuke, Sato, Ryoichi, Nakao, Yoshinori, Ninomiya, Yoshinari, Matsushita, Koichiro, Kamio, Tomohiko, Iijima, Akira
A Study of Knocking Characteristics in a Hydrogen SI Engine under High Compression Ratio2025-32-006311/03/2025
This study investigated the knocking characteristics of a hydrogen spark ignition engine for the purpose of increasing efficiency and expanding the operating range. In recent years, research focused on carbon neutrality has been vigorously conducted, and hydrogen has attracted attention as a next-generation fuel for internal combustion engines (ICEs). The combustion characteristics of hydrogen are vastly from those of existing gasoline. It is essential to have a sufficient understanding of the combustion characteristics of hydrogen in order to develop next-generation ICEs designed to operate on hydrogen fuel. There are especially many aspects of the knocking mechanisms of hydrogen that are unclear. Consequently, those characteristics and mechanisms must be clarified for the purpose of expanding the operating range of hydrogen engines and enhancing their efficiency. In this study, experiments were conducted using a single-cylinder hydrogen engine that was operated at a high compression
Ishihara, Hiromasa, Kishibata, Shunsuke, Miyake, Shota, Iida, Tomoya, Kuwabara, Kenta, Yoshihara, Shintaro, Miyamoto, Sekai, Iijima, Akira
Effect of Plasma-Assisted Ignition on Combustion and Emission Characteristics of Two Stroke Engines with Different Fuels2025-32-003011/03/2025
This study explores the effect of plasma-assisted ignition (PAI) on combustion stability and emissions in two-stroke spark-ignition engines. Two engine platforms were evaluated: a conventional single-cylinder two-stroke engine and a thermodynamically advanced opposed-piston two-stroke (OP2S) engine. The OP2S engine configuration offers reduced heat loss and higher power density due to its uniflow scavenging and favorable geometry, but suffers from high residual gas fraction, which increases ignition difficulty and combustion instability. To address this, nanosecond-pulsed PAI was applied in various spatial arrangements and discharge voltages, using both gasoline and a low-reactivity gasoline/DMC blend fuel. Spark ignition timing was held constant at the minimum advance for best torque across all tests. Combustion stability was assessed via indicated mean effective pressure (IMEP) and its coefficient of variation, while CO and HC emissions were measured as environmental indicators
Liu, Jinru, Yamazaki, Yoshiaki, Otaki, Yusuke, Kato, Hayato, Kobayashi, Daichi, Umegaki, Tetsuo, Asai, Tomohiko, Iijima, Akira
Development of Anti-SideSlip Control for Motorcycles Using IMU2025-32-003711/03/2025
In motorcycle racing and other competitions, there is a technique to intentionally slide the rear wheel to make turns more quickly. While this technique is effective for high-speed riding, it is difficult to execute and carries risks such as falling. Therefore, an anti-sideslip control system that suppresses unintended or excessive sideslip is needed to ensure safe, natural, and smooth turning. In anti-sideslip control, the slip angle is usually used as a control parameter. However, for motorcycles, it is necessary to know the absolute direction of the vehicle's movement. To determine this, GPS or optical sensors are required, but using such sensors for driving is costly and may not provide accurate measurements due to contamination or other environmental factors, making it impractical. Therefore, an anti-sideslip control system was developed by calculating another parameter that indicates the characteristics of the slip angle, without measuring the slip angle itself, thus eliminating
Nakano, Kyosuke, Kawai, Kazunori, Takeuchi, Michinori
Experimental Study of hCNG on Single Cylinder 395cc Spark Ignition Engine for Performance and Exhaust Emission2025-32-005011/03/2025
There is growing demand for energy utilization due to stricter environmental emission norms to reduce greenhouse gases and other threats posed due to the emissions are major motivation factors for researchers to adopt on strategic plans to decrease the usage of energy and reduce the carbon contents of fuels, the usage of hydrogen or blend of hydrogen with CNG as a fuel in internal combustion engines is the best option. As hydrogen has lower volumetric energy density and higher combustion temperature, pure hydrogen-fueled engines produce lower power output and much higher NOx emissions than gasoline-fueled engine at stoichiometric air-fuel ratio. Blending of hydrogen with CNG provides a blended gas termed as hydrogen-enriched natural gas (hCNG). hCNG stands for hydrogen enriched compressed natural gas and it combines the advantages of both hydrogen and methane. The addition of Hydrogen to CNG has potential to even lower the CNG emissions and is the first step towards promotion of a
Syed, Kaleemuddin, Chaudhari, Sandip, Khairnar, Girish, Sajjan lng, Suresh
Computational Investigation on a Boosted Uniflow Scavenged Direct-Injection Combustion Engine (BUSDICE) with Alcohol Fuels2025-32-002711/03/2025
Alcohol fuels, produced from renewable energy sources, are considered a crucial solution for achieving life-cycle carbon neutrality in internal combustion engines. The Boosted Uniflow Scavenged Direct-Injection Combustion Engine (BUSDICE) exhibits significant potential for high thermal efficiency with an aggressive downsizing design. In this study, a computational investigation was carried out to assess the spray mixing and combustion characteristics of BUSDICE fuelled with methanol and ethanol, compared with gasoline, under a high-load condition. The injection duration of methanol and ethanol is significantly longer than that of iso-octane, leading to incomplete evaporation. The mixture exhibits an “outer-rich, central-lean” stratification pattern due to the short mixing time and swirl flow transportation for all three fuels. However, the prolonged injection of methanol induces stronger turbulence, which can enhance the local mixing. The spatial mixture stratification, particularly
Feng, Yizhuo, Lu, Enshen, Dong, Shuo, Keshtkar, Hossein, Wang, Xinyan, Zhao, Hua
Knock Sensors for Two Wheelers Applications2025-32-007911/03/2025
This paper describes the design and characteristics of the knock sensor. The sensor is already used as a commodity product for automotive applications and used by all automotive OEMs for spark ignited combustion engines. With the arrival of the electronic fuel injection on the two wheelers, further optimization of the combustion can be obtained. Although there are many publications on the engine knock strategy, little is known publicly about the sensor itself. The knock sensor is an accelerometer based on a piezoelectric component; it provides an analog signal of the engine vibration. The Electronic Control Unit will filter the signal according to a specific strategy and defines the presence and intensity of the engine knock. The ECU will act accordingly on the ignition timing. The inner structure as well as the mechanical and electrical interface are described in this article.
van Est, Jeroen, Prieu, Corentin
Study on Combustion Detection of a Spark-Ignition Engine with Fuel Variation Using Various Sensors2025-32-005211/03/2025
The use of alternative fuels, such as biofuels and synthetic fuels in small mobility engines has become more common these days. Although these fuels contribute to the carbon neutrality, it is known that they do not have a certain fuel composition, which significantly affects the combustion characteristics of an engine, such as knocking and combustion duration. Therefore, to get the most out of these sustainable fuels, it is necessary to develop engine systems that are highly robust to variations in fuel composition. To achieve this goal, a method to sense fuel characteristics onboard using sensors already widespread in use or can be installed inexpensively is required. Although in-cylinder piezoelectric pressure sensors are useful for research in the laboratory, it is not suitable for the use in commercial engines because of its high cost. Therefore, the use of other sensors should be considered. The purpose of this study is to experimentally analyze what information related to
Hayashi, Kohei, Kim, Jihoon, Yamasaki, Yudai
Firing TDC Identification Through Wasted Spark Duration Measurements During Cranking of Small Engines2025-32-008511/03/2025
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
Irimescu, Adrian, Merola, Simona
Investigation of Transient High Current Ignition for Lean Mixture in Spark Assisted Compression Ignition2025-01-039010/07/2025
Lean burn combustion is an effective strategy to reduce the in-cylinder temperature. Hence reduce NOx emissions and increase the thermal efficiency of the system. One essential aspect of successful combustion is the flame kernel initiation and development. However, as the fuel-air mixture becomes leaner, challenges arise in achieving a stable flame kernel initiation and a moderate speed of flame propagation. This empirical research aims to investigate the impact of the transient high current ignition strategy on flame kernel development, flame propagation and auto-ignition timing of lean Dimethyl Ether (DME). In this work, a rapid compression machine is employed at engine-relevant conditions, a pressure of ~15 bar and temperature of ~650K. Spark-assistance is applied at the end of compression to enable a spark-assisted compression ignition combustion mode. The spark event is initiated by a transient high current ignition system, which includes a traditional transistorized coil ignition
Asma, Sabrina, Yu, Xiao, Jin, Long, Tjong, Jimi, Zheng, Ming
CFD Analysis of Knocking in Hydrogen-Fueled Spark-Ignition Engines with Large Eddy Simulation and Conjugate Heat Transfer2025-01-038910/07/2025
In the pursuit of a carbon-neutral society, hydrogen-fueled power generation engines are gaining considerable attention. However, knocking remains a significant problem that hinders efficiency improvements in hydrogen-fueled spark-ignition (SI) engines. In particular, the large displacement engines, such as those used in cogeneration and distributed energy sources, often face issues with knocking. This is because, with a larger bore and lower rotational speed, there is a higher risk of auto-ignition occurring before the flame has spread throughout the combustion chamber. Knocking is a complex phenomenon influenced by several interrelated physical factors:1) Flow: the non-uniform distribution of fuel concentration and flow velocity within the cylinder; 2) Combustion: the non-uniform propagation of flames affected by the mixture's concentration and flow velocity distribution; 3) Heat Transfer: the non-uniform temperature of the unburned mixture resulting from the temperature distribution
Nomura, Kazutoshi, Suzuki, Keita, Imamori, Yusuke, Fuse, Azusa, Oda, Yuji, Nakano, Hiroki, Tsujimura, Taku, Suzuki, Yasumasa
Bio-Engineered Charcoal for Large Caliber Ignition Systems2025-01-048409/16/2025
Charcoal is a frequently used resource by the DoD with numerous applications. Military charcoal is produced through destructive distillation of a variety of wood types, resulting in a high degree of batch-to-batch variability. Depending on the application of the charcoal, this variability can result in undesirable characteristics in the end-product. To address this issue, DEVCOM AC is examining a charcoal bio-manufactured by DEVCOM CBC using bacteriophages. This highly controlled process results in the consistent production of charcoal with a variety of desirable characteristics, including a high surface area available for combustion due to its porosity as well as a high level of purity. In this effort, DEVCOM AC is investigating this bio-manufactured charcoal as a drop-in replacement in comparison to standard charcoal for applications of interest to boost ignition performance. This work will produce a drop-in-replacement for a DoD-critical resource with improved characteristics
Rozumov, Eugene, Bird, David, Crumbley, Anna, Morris, Lauren, Grau, Henry, Wilson, Daniel, Stern, Aaron, Decker, Robert
ML-based Identification of Lactones for Blend Studies and Combustion Performance in a Spark-Ignition CFR Engine2025-24-007109/07/2025
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
Sirna, Amanda, Loprete, Jason, Ristow Hadlich, Rodrigo, Assanis, Dimitris, Patel, Rutvi, Mack, J. Hunter
Methodology for the Study of Hydrogen Combustion in an Optical Spark Ignition Engine2025-24-006209/07/2025
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
Pastor, Jose V., Novella, Ricardo, Tejada, Francisco J., Cáceres-Carías, José
Numerical Analysis of the Combustion Process in a Pre-Chamber Marine Engine Fueled with Ammonia-Hydrogen Mixtures2025-24-002109/07/2025
Ammonia and hydrogen, as carbon-neutral fuels, possess the potential to play a crucial role in the decarbonization of the mobility sector. This research examines the optimization of the combustion process in a marine spark-ignition engine through the use of a passive pre-chamber. The study has been carried out using computational fluid dynamics (CFD) models. Considering a hydrogen content in the fuel blend of 15% by volume, at a fixed equivalence ratio equal to 0.8, two different nozzle diameters have been tested, and the optimal spark timings have been identified. Then, the effect of different hydrogen amounts in the fuel mixture on the engine’s performance and emissions has been assessed. An optimal spark timing of 712 CAD has been found for both 3 mm and 5 mm nozzles at the specified operating point. The 5 mm nozzle provides slightly higher IMEPH and gross efficiency, with minimal impact on emissions. Reducing hydrogen in the fuel blend from 15% to 10% lowers IMEPH from 31 to 12 bar
D'Antuono, Gabriele, Lanni, Davide, Galloni, Enzo, Fontana, Gustavo
Overview of Current Developments of Pre-Chamber Spark Plugs for Passenger Car Applications2025-24-015209/07/2025
The internal combustion engine (ICE) is projected to remain the dominant technology in the transport sector over the short to medium term, and there exists significant potential for further improvements in fuel economy and emission reductions. One promising approach to enhancing the efficiency of spark ignition engines is the implementation of passive pre-chamber spark plugs. The primary advantages of pre-chamber-initiated combustion include the mitigation of knocking, an increase in in-cylinder turbulence, and a combustion process that is both faster and more stable compared to that achieved with conventional J-gap spark plugs. Additionally, the higher ignition energy provided by pre-chamber spark plugs enables operation under higher intake pressures, maintains similar exhaust gas recirculation rates, and supports leaner combustion conditions. These benefits are predominantly attributed to volumetric ignition via hot, reactive jets. However, the pre-chamber spark plug also presents
Korkmaz, Metin, Juressen, Sven Eric, Rößmann, Dominik, Kapus, Paul E., Pino, Sandro
Investigation of the Combustion Process of a Thermally Conditioned Active Prechamber in Monovalent Operation with Ammonia2025-24-002809/07/2025
The debate over synthetic fuels is intense especially in sectors with a high energy demand like maritime [1, 2]. Hydrogen production from renewable sources is growing, but immediate measures for decarbonization are needed [3, 4]. In this context, the project MethMag was funded, and a gas engine for methane combustion with an innovative cooling concept and a purged prechamber (PC) spark plug was virtually developed [5, 6]. Validation with data from the test bench demonstrates that the simulations accurately represent the operating conditions [7, 8]. This combustion process is adapted for ammonia, which is being considered as a climate-friendly fuel of the future, particularly in maritime transportation [4, 9]. This fuel faces significant combustion challenges and is therefore mostly considered in complex, bivalent systems [10]. In particular, the prechamber is examined regarding the ignitability of ammonia. The overarching objective is to eliminate the necessity for a secondary fuel
Rothe, Paul, Bikas, Georgios, Mauss, Fabian
Ammonia Combustion with Ignition Improvement Measures in a High-Speed Marine Application2025-24-002509/07/2025
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
Li, Zhengling, Lückerath, Moritz, Pischinger, Stefan, Boberic, Aleksandar, Franzke, Bjoern, Dhongde, Avnish, Jagodzinski, Bartosch, Burrows, John, Korkmaz, Metin
In-Cycle Predictability and Control of Knock in a PFI HD SI Engine Fueled with Methanol2025-24-001909/07/2025
Knock is an anomalous combustion occurrence limiting the efficiency of the spark-ignited engine, hence increasing fuel consumption and emissions. The global aim to cut the emissions from green-house-gases therefore makes knocking combustion a very appropriate research topic of today. This paper explores the possibility to do in-cycle spark timing control of knock, based upon cycle-to-cycle adaptation of the temperature of a hypothesized hot spot. The potential for post-spark timing control is also examined. Experiments were carried out on a single cylinder port fuel injected spark ignited engine fueled with methanol. Knock was quantified by the Maximum Amplitude of Pressure Oscillations metric and predicted by the Livengood-Wu integral. Normalized distributions, together with different σ confidences, of the in-cylinder state such as gas temperature, in-cylinder pressure and Livengood-Wu integral were computed both pre- and post-spark timing. Type I and Type II errors of the computed
Ainouz, Filip, Lius, Andreas, Cronhjort, Andreas, Stenlaas, Ola
Toward Sustainable Heavy-Duty Transport: Evaluating Charge Dilution and Advanced Corona Ignition System Effects on SI Natural Gas Engine Efficiency and Combustion Characteristics2025-24-002409/07/2025
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
Di Domenico, Davide, Napolitano, Pierpaolo, Papi, Stefano, Ricci, Federico, Golini, Stefano, Rapetto, Nicola, Giordana, Sergio, Beatrice, Carlo
Numerical and Experimental Investigation of a Pre-Chamber Igniter for Enhanced Low Load Stability in Internal Combustion Engines2025-24-000209/07/2025
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
Fellner, Felix, Härtl, Martin, Jaensch, Malte, D'Elia, Matteo, Burgo Beiro, Marcos, Nambully, Suresh Kumar, Rothbauer, Rainer
Experimental and Numerical Study on the Performance and Exhaust Emissions of a Single-Cylinder Natural Gas Large Bore Engine Equipped with Passive Pre-Chamber2025-24-002209/07/2025
The maritime industry is among the most energy-intensive sectors, and achieving fleet decarbonization is crucial to significantly reduce greenhouse gas emissions. As a transitional fuel, natural gas (NG) presents a viable short-to-midterm solution. Compared to conventional marine fuels, NG has the potential to lower carbon dioxide emissions by approximately 20–30%. However, to fully leverage this potential on carbon footprint reduction, substantial advancements in combustion technologies are required. One promising approach to enhance the efficiency of SI NG engines is the implementation of Passive Pre-Chamber (PPC) technology. This strategy enables leaner combustion, improving thermal efficiency, mitigating the occurrence of knocking, and reducing NOx emissions. This study presents both experimental and numerical investigations to analyze the impact of charge dilution and ignition timing on the performance and emissions of a single-cylinder prototype NG PPC SI engine for marine
Marchitto, Luca, Pesce, Francesco, Accurso, Francesco, Tornatore, Cinzia, Gorietti, Valentina, Buzzi, Luca, Grosso, Alessandro, Luci, Matteo, Napolitano, Pierpaolo, Pennino, Vincenzo, Beatrice, CARLO, Di Domenico, Davide, Giardino, Angelo
Combustion Characteristics and Efficiency of a Turbocharged Hydrogen-Fueled Internal Combustion Engine Under Ultra-Lean, High-Load Conditions2025-24-004809/07/2025
The transportation industry seeks sustainable alternatives to fossil fuels, and hydrogen internal combustion engines (H₂ICE) have emerged as a practical solution. They offer near carbon-free operation while integrating with existing engine technology and infrastructure. Thanks to hydrogen’s specific properties, lean combustion can be achieved, significantly reducing NOx emissions. However, operating a commercial engine under ultra-lean conditions at high load presents challenges, particularly in maintaining volumetric efficiency and power density. This study analyzes the combustion behavior, NOx emissions, and loss mechanisms in a four-cylinder, direct-injection, hydrogen-fueled engine, equipped with a variable geometry turbine (VGT). The engine was tested at three BMEP levels (8, 10, and 12 bar) under ultra-lean conditions, with lambda varied between 2.2 and 3.6. Unlike conventional approaches, fuel mass was held constant at each load, and lambda was adjusted by varying intake air
Azizianamiri, Sobhan, Tauzia, Xavier, Maiboom, Alain, Perrot, Nicolas
Parametric Analysis of Performance and Efficiency of Free-Piston Linear Generators with 1D and CFD Simulations2025-24-010509/07/2025
High efficiency, fuel flexibility, and seamless integration with electrified systems are fundamental prerequisites for the next generation of internal combustion engines. In this context, the free-piston linear generator (FPLG) evolves the traditional internal combustion engine concept (ICE) by replacing the crankshaft mechanism with a linear generator, directly converting piston motion into electricity. The FPLG offers several advantages, including higher efficiency in converting mechanical energy to electricity, the ability to operate with a variable compression ratio, and reduced heat losses during the expansion stroke. Among the various tested architectures, the two-stroke, opposed-piston FPLG appears to be the most promising. However, detailed numerical and experimental investigations are necessary to fully understand how performance and efficiency are influenced by the intricate interplay of processes governing electricity generation. In particular, the significant differences
Morandi, Nicola, Lucchini, Tommaso, Gianetti, Giovanni, Baratta, Mirko, Misul, Daniela, Santonocito, Fabrizio
Development of a Compact Hydrogen Engine for Commercial Applications2025-24-006009/07/2025
As the individual and commercial vehicle industries seek sustainable alternatives to conventional internal combustion engines (ICEs), hydrogen-fueled rotary engines are emerging as a promising solution for several applications. This paper presents an innovative approach for the development of a hydrogen rotary engine that is integrated within a hybrid system. By exploiting the unique characteristics of rotary engines, such as compact size and high power-to-weight ratio, the electric machine, the battery and the rotary engine can be accommodated in the installation space of a conventional ICE with comparable power, despite the reduced power density of hydrogen as a fuel in ICEs. As a first step, the hydrogen engine is naturally aspirated and equipped with direct injection. To develop a suitable calibration for the engine’s application, the influence of calibration parameters such as ignition and injection are investigated. The study examines the influence of these on operating behavior
Endres, Jonas, Beidl, Christian, Hofmann, Silas
Smart Ignition Coil for H2 ICE Application with Combustion Diagnostic System for Misfire Detection2025-24-005809/07/2025
The transition to decarbonized transportation necessitates significant modifications to internal combustion engines for alternative carbon-neutral fuels, particularly hydrogen. The integration of alternative systems is crucial for improving engine control, facilitating real-time engine health monitoring and facilitate early problem detection. This study investigates the potentialities of an ignition system specifically designed for H2 applications, with the integration of a smart coil diagnostic system with the aim to enhance engine performance and control capabilities. Experiments were conducted on a single-cylinder research engine across varying spark advanced, throttle positions, and engine speeds, comparing the novel ignition system with integrated diagnostics against traditional spark plug. Results demonstrate improvements in combustion stability and control when innovative spark plug was employed. Compared to a conventional spark plug, the Hy2Fire® system consistently delivered
Ricci, Federico, Papi, Stefano, Avana, Massimiliano, Dal Re, Massimo, Grimaldi, Carlo
A Study on Sensitive Spots in Hydrogen Engines2025-24-005909/07/2025
Premature self-ignitions in hydrogen internal combustion engines have been associated with the presence of hot spots. However, local increases in charge reactivity may be triggered not only by elevated temperatures but also by composition inhomogeneities. Such non-uniformities, in addition to imperfect mixing (e.g., in the case of direct hydrogen injection), may result from external contamination by more reactive components, such as lubricant oil. The present study aims to shed light on the mechanism through which lubricant oil contamination leads to the formation of sensitive spots, by analysing the behaviour of an isolated droplet suspended in a hydrogen/air environment. The “HyLube” chemical kinetic mechanism was employed to reproduce the chemical behaviour of lubricant oil, as it was specifically developed for this purpose. A one-dimensional numerical model was used to simulate the heating, vaporization, and combustion of the droplet. Zero-dimensional simulations were also
Distaso, Elia, Baloch, Daniyal Altaf, Amirante, Riccardo, Tamburrano, Paolo
Calorimetric Study of the Influence of Spark Ignition System Parameters on the Energy Transfer to the Gas2025-24-003309/07/2025
Achieving a robust ignition with minimal spark plug wear is challenging in heavy duty engines fueled with gaseous fuels like biogas and hydrogen. Thermal energy deposition from the spark to the gas was studied in a 10.9 milliliter custom-built spark calorimeter. An AC capacitive ignition system was used along with a dual-nickel standard J-gap spark plug and the influence of multiple physical and electrical parameters was investigated in an experimental design including five factors: spark plug center electrode diameter, electrode gap, glow current, glow duration, and gas density. The aim was to maximize energy transfer to the gas and reduce heat losses to the spark plug electrodes, thus extending spark plug service life and reducing the risk of pre-ignition in hydrogen engines caused by overheated electrodes. The results show that the electrode gap has the dominating influence on energy transfer to the gas. Both the gas density and the glow current contribute to increased energy
Saha, Anupam, Tunestal, Per, Aengeby, Jakob, Andersson, Oivind
Numerical Investigation of Lean Neat Ammonia Combustion in a Heavy-Duty Diesel Engine Converted to Spark Ignition2025-24-003209/07/2025
Ammonia (NH3) use as fuel poses technical challenges such as increased nitrogen-based and unburned NH3 emissions. This study used a 0D model coupled with detailed NH3 kinetics to evaluate the effect of equivalence ratio (ϕ) from 0.7 to 1.0 in a heavy-duty compression ignition engine converted to spark ignition operation. The goal was to evaluate how ϕ affected NOx and N2O formation and/or destruction at constant fuel energy per cycle, engine speed, and CA50. Simulated NOx emissions (i.e., NO + NO2) followed a trend similar to the one typically observed for hydrocarbon fuels in a SI engine, but that was different from the experiment. In addition, it underpredicted NOx emissions for ϕ = 0.7 by 79% and overpredicted NOx emissions for ϕ = 1 by 576%. The simulation showed that thermal NO production was more than 80% from the total NO production, but the effect of ϕ on this percentage was negligible. Then, predicted N2O emissions had an opposite trend and were three orders of magnitude lower
Saenz Prado, Stefany, Alvarez, Luis F., Trujillo Grisales, Juan M., Akkerman, Vyacheslav, Dumitrescu, Cosmin E.
Computational Fluid-Dynamics Analysis of the Effect of Ethanol-Air Mixture Supply in a Heavy-Duty Engine2025-24-002909/07/2025
As part of the Bio-FiRE-for-EVer research project aiming to propose a solution for off-grid charging stations based on the adoption of a reciprocating engine, this study investigated the combustion development and pollutant emissions of an 8.7 l six-cylinder heavy-duty PFI internal combustion engine fueled by ethanol. The reference experimental case features critical issues in the formation of the air-fuel, mainly due to the slow evaporation rate of the alcohol fuel inside the intake manifold via a single point injection, providing a non-uniform and averagely rich (λ=0.89) reactant mixture inside the cylinders. For this purpose, an in-depth analysis of the in-cylinder phenomena is performed by using a CFD solver for the reacting flow. A geometry of the cylinder system complete with intake and exhaust ducts is created for calculations with the three-dimensional Ansys FORTE code. The inclusion of the inlet duct in the computational domain allows the experiencing of several setups of the
De Robbio, Roberta, Cameretti, Maria Cristina, Palomba, Marco, Tuccillo, Raffaele
Optical Diagnostic Analysis of Methane Combustion Performance and Emissions While Incorporating Ammonia and Multiple Flames In A Spark-Ignition Engine2025-24-002309/07/2025
The utilization of methane–ammonia fuel blends in spark-ignition engines represents a viable strategy for reducing carbon emissions while capitalizing on the high hydrogen content and carbon-free nature of ammonia. Methane, characterized by its high octane number and low carbon content, offers improved thermal efficiency, higher compression ratios, and reduced pollutant emissions relative to conventional gasoline fuels. Ammonia, despite its advantageous energy density and zero carbon content, suffers from low flame speed and high ignition temperature, which pose challenges for stable combustion. Blending ammonia with methane addresses these limitations by enhancing ignition characteristics and flame stability while simultaneously reducing carbon-based emissions. This study examines the combustion and emission behavior of methane–ammonia blends in a single-cylinder, four-stroke engine under varying spark ignition configurations. Experiments were conducted across a range of ammonia
Uddeen, Kalim, Tang, Qinglong, Shi, Hao, Turner, James
Enhancing Ammonia Combustion in Heavy-Duty SI Engines: A 3D-CFD Study on Pre-Chamber Ignition, Methane Addition, and Spark Timing Optimization2025-24-000609/07/2025
Ammonia is a promising fuel for achieving zero-carbon emissions in internal combustion engines. However, its low flame speed and heat of combustion pose significant challenges for efficient combustion. The pre-chamber (PC) spark-ignition (SI) system offers a viable solution by generating multiple ignition points in the main chamber (MC), enhancing combustion efficiency and enabling at the same time lean-burn operation. This study investigates the combustion characteristics and emissions of an active PC spark-ignition heavy-duty engine fueled with ammonia and ammonia-methane mixtures through numerical 3D-CFD simulations performed using the CONVERGE software. These simulations provide an accurate representation of the complex chemical and physical phenomena occurring within the combustion chamber. The study starts from a fully methane-fueled case, validated against experimental data, and subsequently explores different ammonia-methane mixtures. Then, a detailed spark timing (ST) analysis
Palomba, Marco, Salahi, Mohammad Mahdi, Cameretti, Maria Cristina, Mahmoudzadeh Andwari, Amin
Comparison between Spark-Ignition and Passive Pre-Chamber Combustion in a Methanol Fuelled Heavy-Duty Engine at Different Speeds, Loads, and EGR Dilutions2025-24-003009/07/2025
Decarbonizing the transport sector requires solutions that reduce CO₂ emissions while improving the efficiency of existing engine platforms. This study explores a retrofit strategy in which a heavy-duty diesel engine is converted to Otto-cycle operation and equipped with a passive pre-chamber combustion (PPCC) system. Methanol was used as the fuel due to its high octane number, low carbon intensity, and favourable combustion properties. The performance of the PPCC system is experimentally compared to conventional spark ignition (SI) across varying engine speeds, loads, and exhaust gas recirculation (EGR) levels. A dual-dilution strategy, combining lean operation (λ = 1.6) with EGR, was applied to extend dilution tolerance and assess the feasibility of operating near stoichiometry. All tests were conducted under steady-state conditions with fixed spark timing. Results show that PPCC consistently delivers faster combustion than SI across all conditions, with greater stability and reduced
Fong Cisneros, Eric J., Hlaing, Ponnya, Cenker, Emre, AlRamadan, Abdullah, Turner, James WG
High Tension Ignition Cable Assemblies - MarineJ1191_202508 (Current)08/18/2025
This Standard covers the requirements for all marine inboard and outboard gasoline engine ignition assemblies and components.
Marine Technical Steering Committee
Ignition System Nomenclature and TerminologyJ139_202508 (Current)08/15/2025
To provide standard terminology and definitions with regard to ignition systems for spark-ignited internal combustion engines.
Ignition Standards Committee
Numerical Analysis of Direct-Injection and Combustion Inside a H2 Engine2025-01-030107/02/2025
The direct injection of hydrogen (H2) inside internal combustion engines (ICEs) is gaining large research interest over the port-fuel injection strategy, because of several advantages as higher volumetric efficiencies, increased power output and reduced risks of abnormal combustion. However, the required high pressure ratios across the injector nozzle produce moderate-to-high under-expanded jets, characterized by complex flow structures. This poses a challenge for the numerical modelling of the mixture preparation by means of 3D computational fluid dynamics (CFD) approaches. In this work, a validated 3D-CFD methodology has been employed to simulate the closed-valve cycle of a direct injection H2 engine equipped with a centrally mounted hollow-cone injector and a non-axisymmetric piston bowl. First, injection and mixture preparation have been studied considering an early injection at the beginning of the compression stroke, and a delayed injection in the second half of the compression
Capecci, Marcolucio, Sforza, Lorenzo, Lucchini, Tommaso, D'Errico, Gianluca, Pezza, Vincenzo, Tosi, Sergio
Variable Valve Actuation and Multiple Injections to Enhance the Gas Exchange of a Passive Pre-Chamber Igniter2025-01-031507/02/2025
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
Fellner, Felix, Härtl, Martin, Jaensch, Malte
Experimental Investigation of Performance and Emission Characteristics of a Diesel Light-Duty Engine Fuelled with Pure Hydrogen2025-01-031407/02/2025
Transitioning to zero-carbon fuels is pivotal for expediting the reduction of carbon emissions. Hydrogen demonstrates significant adaptability and emerges as a principal zero-carbon alternative fuel for fossil fuel internal combustion engine (ICE) platforms. Implementing hydrogen in both spark ignition (SI) and compression ignition (CI) engines has proven to be both economically viable and timely. In this study, a conventional diesel engine was operated with pure hydrogen with minimal modification to engine hardware. It features a proactive, automated shutdown system to mitigate intake backfire risks associated with hydrogen port fuel injection (PFI) systems. A comprehensive engine characterisation was conducted using a lambda sweep test, measuring values from 1.5 to 4.5 with an integrated in-cylinder pressure transducer for high-resolution data. The study used an advanced Bandpass, Rectify, Integrate, Compare (BRIC) knock detection method for engine health monitoring and assessed
Mohamed, Mohamed, Zaman, Zayne, Lu, Enshen, Feng, Yizhuo, Wang, Xinyan, Zhao, Hua
Comparison of Spark and Turbulent Jet Ignition in a Fully Ammonia-Fueled Engine2025-01-020106/16/2025
Ammonia (NH3) is an emerging carbon-free fuel with the potential to decarbonize the energy sector. However, its widespread adoption is hindered by challenges like low flame speed, high ignition energy, elevated emissions of nitrogen oxides (NOx), and unburned NH3. These limitations necessitate innovative combustion strategies for efficient and stable engine operation. This study investigates the potential of turbulent jet ignition (TJI) to overcome these challenges through the implementation of a pre-chamber, a small auxiliary chamber equipped with a spark plug to create hot, reactive jets that propagate into the main chamber, promoting rapid combustion from distributed ignition sites. In this work, TJI operation is compared to conventional spark ignition (SI) in a diesel engine platform retrofitted for 100% ammonia operation. Experiments were conducted at 1200 and 1800 RPM across varying loads (25%, 50%, 75%, and 100%) with equivalence ratio and spark timing sweeps. Combustion
Dhotre, Akash, Voris, Alex, Okey, Nathan, Kane, Seamus, Northrop, William
Parametric Analysis of Injector Operational Parameters, Charge Dilution, and Intake Valve Opening on In-Cylinder Motion and Flame Development in an Automotive, Lean-Burn, Gasoline Engine with High-Tumble2025-01-019806/16/2025
The effect of injection pressure, start of injection (SOI) timing, charge dilution, and valve timing on charge motion and early flame development was investigated for a pre-production automotive gasoline engine. Experiments were performed in a single-cycle optical engine designed to represent the high-tumble (Tumble ratio = 1.8), lean-burn engine. Time-resolved particle image velocimetry (PIV) was used to characterize velocity flow fields throughout the swept volume during the intake and compression strokes. Diffuse back illuminated imaging allowed for visualization and quantification of the injected liquid fuel spray and its interactions with the tumble vortex. Hydroxyl (OH*) chemiluminescence imaging was performed to image spark channel elongation and early flame kernel development. It was observed that an optimal injection timing of 320° before top dead center (bTDC) resulted in attenuation of the tumble motion and an associated reduction in compression flows that shifted the tumble
MacDonald, James, Ekoto, Isaac, Han, Donghee, Lee, Jonghyeok
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