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Ultra-lean combustion of GDI engine could achieve higher thermal efficiency and lower NOx emissions, but it also faces challenges such as ignition difficulties and low-speed flame propagation. In this paper, the sparked-spray is proposed as a novel ignition method, which employs the spark to ignite the fuel spray by the cooperative timing control of in-cylinder fuel injection and spark ignition and form a jet flame. Then the jet flame fronts propagate in the ultra-lean premixed mixture in the cylinder. This combustion mode is named Sparked-Spray Induced Combustion (SSIC) in this paper. Based on a 3-cylinder 1.0L GDI engine, a 3D simulation model is established in the CONVERGE to study the effects of ignition strategy, compression ratio, and injection timing on SSIC with a global equivalence ratio of 0.50. The results show it is easier to form the jet flame when sparking at the spray front because the fuel has better atomization and lower turbulent kinetic energy at the spray front.

Ammonia is employed as the carbon-free fuel in the future engine, which is consistent with the requirements of the current national dual-carbon policy. However, the great amount of NOx and unburned NH3/H2 in the exhaust emissions is produced from combustion of ammonia and is one kind of the most strictly controlled pollutants in the emission regulation. This paper aims to investigate the NOx and unburned NH3/H2 generative process and emission characteristics by CFD simulation during the engine combustion. The results show that the unburned ammonia and hydrogen emissions increase with an increase of equivalence ratio and hydrogen blending ratio. In contrast, the emission concentrations of NOx, NO, and NO2 decrease with the increasing of equivalence ratio, but increase with hydrogen blending ratio rising. The emission concentration of N2O is highly sensitive to the O/H group and temperature, and it is precisely opposite to that of NO and NO2.

Recently, it has been wildly recognized that active pre- chamber has a significant effect on extending the lean burn limit of gasoline engines. Ion current signals in the combustion is also considered as a promising approach to the engine knock detection. In this study, the feasibility of employing ion current in an active pre- chamber for combustion diagnosis was analyzed by three-dimensional numerical simulation on a single- cylinder engine equipped with active pre-chamber. The flow characteristics of charged species (NO+, H3O+ and electrons) in the main chamber and pre-chamber under knock conditions are investigated at different engine speeds, intake pressures and ignition timings. The results show that the ion current can theoretically be used for the knock detection of the active pre- chamber. The peak value of the electron or H3O+ mass fraction caused by knocking backflow can be used as knock indication peak.

As an efficient hydrogen carrier, ammonia itself is also a promising zero-carbon fuel that is drawing more and more attention. As the combustion of pure ammonia is hard to achieve on SI engines, in this study, spark- ignited micro-gasoline-jet was utilized to ignite the premixed ammonia/air mixture in a constant volume combustible vessel at different premixed ammonia/air excess air coefficient and backpressure (represented by ammonia partial pressure). The flame image was captured by a high-speed camera and the transient pressure change in the vessel was measured by an engine cylinder pressure sensor.

In the ultra-lean combustion mode, the combustion temperature is relatively low, which is expected to avoid the high-temperature NOx generation. And it also can use excess air to fully oxidize CO, HC and Soot, to achieve cleaner combustion. But at the same time, ultra-lean combustion has difficulties in ignition and flame propagation. This paper used CONVERGE to simulate the combustion process and products of a new ultra-lean combustion mode, which ignited the ultra-lean premixed fuel/air mixture with the spark-ignited micro-fuel-jet, in a constant-volume vessel with a 6-hole GDI injector. The differences of combustion processes and products were simulated for two spark-ignition positions, including ‘on’ the micro-jet spray and ‘between’ two micro-jet sprays. It was found that the combustion duration (the time for burned-fuel-ratio from 10% to 90%) could be shortened by about 14.3% if igniting ‘on’ the micro-jet spray, but the amount of NOx generated would increase about 21.0%.

The argon power cycle engine, which uses hydrogen as fuel, oxygen as oxidant, and argon other than nitrogen as the working fluid, is considered as a novel concept of zero-emission and high-efficiency system. Due to the extremely high in-cylinder temperature caused by the lower specific heat capacity of argon, the compression ratio of spark-ignition argon power cycle engine is limited by preignition or super-knock. Compression-ignition with direct-injection is one of the potential methods to overcome this challenge. Therefore, a detailed flammability limit of H2 under Ar-O2 atmosphere is essential for better understanding of stable autoignition in compression-ignition argon power cycle engines.

Low heat rejection (LHR) combustion has been recognized as a potential technology for further fuel economy improvement. This paper aims to simulate how the piston top’s thermal barrier coating affects the engine’s thermal efficiency and emissions. Accordingly, a Thin-wall heat transfer model in AVL Fire software was employed. The effects of increasing the piston top surface temperature, comparing different thermal barrier coating material, were simulated at the engine’s rated power operating point, so as the piston top’s surface roughness. In comparison to a standard diesel engine, the indicated thermal efficiency (ITE) could increase by 0.4% when the surface temperature of the piston top changed from 575K to 775K.

For internal combustion engine systems, lean and diluted combustion is an important technology applied for fuel efficiency improvement. Because of the thermodynamic boundary conditions and the presence of in-cylinder flow, the development of a well-sustained flame kernel for lean combustion is a challenging task. Reliable spark discharge with the addition of enhanced delivered energy is thus needed at certain time durations to achieve successful combustion initiation of the lean air-fuel mixture. For a conventional transistor coil ignition system, only limited amount of energy is stored in the ignition coil. Therefore, both the energy of the spark discharge and the duration of the spark discharge are bounded. To break through the energy limit of the conventional transistor coil ignition system, in this work, an adaptive spark ignition system is introduced. The system has the ability to reconstruct the conductive ion channels whenever it is interrupted during the spark discharge.

A hot exhaust gas burner system is applied to break through the limitations of the traditional diesel engine bench. Sufficient atomization is needed to realize spark ignition in a low-pressure burner system. Hence, the design of the atomization system is studied both experimentally and numerically. Through the reasonable optimization of the nozzle diameter, the air assist pressure, the angle among the four nozzles of four V-structures as well as the diameter and the angle of co-flow holes, an even distribution of small diesel droplets in the ignition area of the burner is realized. Consequently, diesel spray can be spark ignited in a low-pressure burner system, which can simulate the diesel exhaust. And the DPF can be installed downstream of the burner to quickly analyze the effect of ash accumulation on the DPF.

The conventional transistor coil ignition system with coil-out energy up to 100 mJ might not be sufficient to establish a self-sustained flame kernel under lean combustion with strong in-cylinder flow motion. Further increase of the discharge current will decrease the voltage across the spark gap, which will affect the calculation of the energy delivered to the spark gap. In this paper, the relationship between the discharge current and gap voltage is investigated, and it is discovered that the spark energy doesn,t increase monotonously with the increase of the discharge current. However, engine test results still indicate a positive impact of discharge current amplitude on the engine performance.

The performances of heavy-duty natural gas engines have been limited by combustion temperature and NOx emissions for a long time. Recently, water injection technology has been widely considered as a technical solution in reducing fuel consumption and emissions simultaneously in both gasoline and diesel engines. This paper focuses on the impacts of intake manifold water injection on characteristics of combustion and emissions in a natural gas heavy-duty engine through numerical methods. A computational model was setup and validated with experimental data of pressure traces in a CFD software coupled with detailed chemical kinetics. The simulation was mainly carried out in low-speed and full-load conditions, and knock level was also measured and calculated by maximum amplitude of pressure oscillations (MAPO).

The present work discusses the effects of intake manifold water injection in a six-cylinder heavy duty natural gas (NG) engine through one-dimensional simulation. The numerical study was carried out based on GT-Power under different engine working conditions. The established simulation model was firstly calibrated in detail through the whole engine speed sweep under full load conditions before the model of intake manifold water injector was involved, and the calibration was based on experimental data. The intake manifold water injection mass was controlled through adjustment of intake water/gas (water/natural gas) ratio, a water/gas ratio swept from 0 to 4 was selected to investigate the effects of intake manifold water injection on engine performance and emissions characteristics. On the other hand, the enhancement potential of intake manifold water injection in heavy duty NG engine under lean and stoichiometric condition was also investigated by the alteration of air-fuel ratio.

The present work discusses a novel oxy-fuel combustion cycle utilized in compression ignition internal combustion engine. The most prominent feature of this cycle is that the air intake is replaced by oxygen; therefore nitric oxide (NOX) emission is eliminated. The enrichment of oxygen leads to higher flame speed and mass fraction consumption rate; on the other hand, the high concentration of oxygen presented during combustion will result in intense pressure rise rate which may cause severe damage to engine hardware. As water injection is already utilized in gasoline engine to control knocking, the utilization of water injection in optimizing oxy-fuel combustion process has been tested in this study. To understand the relationship between water injection strategy and cycle efficiency, computational fluid dynamics (CFD) simulations were carried out. The model was carefully calibrated with the experimental results; the errors were controlled within 3%.

This paper presents a study of the Hydrogen/Argon lifted flames in a hot vitiated co-flow. The effects of the dilution of argon in central fuel, the volume fraction of argon in the central fuel, co-flow temperature and the velocity of the central jet on the flame lift-off length were studied, and the numerical simulation with PDF model were analyzed as well. The results could provide theoretical supports for the research of the hydrogen fueled argon cycle engine which is a potential way not only to increase the indicated thermal efficiency of internal combustion engine but also realize the zero emission. The result shows that at the same boundary condition the central jet of H2+Ar has a lower lift-off length than the central jet of H2+N2. By the numerical simulation, the jet flame of H2+Ar has a higher maximum temperature and maximum OH concentration. It indicated that the dilution of argon could promote the combustion reaction.

Spark ignition systems with the capability of providing spark event with either higher current level or longer discharge duration has been developed in recent years to help IC engines towards clean combustion with higher efficiency under lean/diluted intake charge. In this research, a boosted current spark strategy was proposed to investigate the effect of spark discharge current level and discharge duration on the combustion process. Firstly, the discharge characteristics of a boosted current spark system were tested with a traditional spark plug under crossflow conditions, and results showed that the spark channel was more stable, and was stretched much longer when the discharge current was boosted. Then the boosted current strategy was used in a spark ignition engine operating under lean conditions. Boosted current was added to the spark channel with different timing, duration, and current levels.

Pre-ignition may lead to an extreme knock (super-knock or mega-knock) which will impose a severe negative influence on the engine performance and service life, thus limiting the development of downsizing gasoline direct injection (GDI) engine. More and more studies reveal that the auto-ignition of lubricants is the potential source for pre-ignition. However, pre-ignition is complicated to study on the engine test bench. In this paper, a convenient test method is applied to investigate the influence of lubricants metal-additives on pre-ignition. 8 groups of lubricants are injected into a hot co-flow atmosphere which generated by a burner. A single-hole nozzle injector with a diameter of 0.2 mm at 20 MPa injection pressure is utilized for lubricants' injection and spray atomization. The ignition delays of lubricants with different additives of calcium, ZDDP (Zinc Dialkyl Dithiophosphates) and magnesium content under the hot co-flow atmosphere are recorded with a high-speed camera.

The work of this paper aimed at investigating the cyclic variations of argon power cycle engine with fuel of hydrogen at lean burn operating conditions. The engine had been modified based on a 0.402 L, single-cylinder diesel engine into spark ignition engine with a port fuel injection system. The influencing factors on the cyclic variations, such as ignition timing, engine speed and compression ratio, were tested in this study. In all tests, the throttle opened at 0%, and the excess oxygen coefficient was maintained at 2.3. The results showed that as the ignition timing retards, CoVPmax and CoV(dp/dφ)max of argon power cycle engine increased, while CoVIMEP decreased firstly and increased afterward. And there is an ignition timing to make the lowest CoVIMEP, which is not consistent with MBT.

Downsizing gasoline direct injection engine with turbo boost technology is the main trend for gasoline engine. However, with engine downsizing and ever increasing of power output, a new abnormal phenomenon, known as pre-ignition or super knock, occurs in turbocharged engines. Pre-ignition will cause very high in-cylinder pressure and high oscillations. In some circumstances, one cycle of severe pre-ignition may damage the piston or spark plug, which has a severe influence on engine performance and service life. So pre-ignition has raised lots of attention in both industry and academic society. More and more studies reveal that the auto-ignition of lubricants is the potential source for pre-ignition. The auto-ignition characteristics of different lubricants are studied. This paper focuses on the ignition delay of different lubricants in Controllable Active Thermo-Atmosphere (CATA) combustion system.

The development of the present day spark ignition (SI) engines has imposed higher demands for on-board ignition systems. Proper design of the ignition system circuit is required to achieve certain spark performances. In this paper, the authors studied the relationship between spark discharge characteristics and different inductive spark ignition circuit parameters with the help of a simplified circuit model. The circuit model catches the principle behavior of the spark discharge process. Simulation results obtained from the model were compared with experimental data for model verification. Different circuit model parameters were then tuned to study the effect of those on spark discharge current and spark energy properties. The parameters studied include the ignition coil coupling coefficient, ignition coil primary and secondary inductances, secondary circuit series resistance and spark plug gap width.

Research studies have suggested that changes to the ignition system are required to generate a more robust flame kernel in order to secure the ignition process for the future advanced high efficiency spark-ignition (SI) engines. In a typical inductive ignition system, the spark discharge is initiated by a transient high-power electrical breakdown and sustained by a relatively low-power glow process. The electrical breakdown is characterized as a capacitive discharge process with a small quantity of energy coming mainly from the gap parasitic capacitor. Enhancement of the breakdown is a potential avenue effectively for extending the lean limit of SI engine. In this work, the effect of high-power capacitive spark discharge on the early flame kernel growth of premixed methane-air mixtures is investigated through electrical probing and optical diagnosis.