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Both ammonia and hydrogen, as zero-carbon fuels for internal combustion engines, are received growing attention. However, ammonia faces a challenge of low flame propagation velocity. Through injecting hydrogen into active pre-chamber, its jet flame ignition can accelerate the flame propagation velocity of ammonia. The influence of different pre-chamber structures on engine combustion characteristics is significant. In this paper, numerical studies were conducted to assess the impact of various pre-chamber structures and hydrogen injection strategy on the combustion characteristics of ammonia/hydrogen engines while maintaining the equivalent ratio of 1.0. The results indicate that the jet angle significantly affects the position of jet flame and the followed main combustion. The in-cylinder combustion pressure peaks at jet angle of 150°. Meanwhile, the combustion duration of 150° is shortened by 74.3% compared with that of 60°.

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.

As a novel ignition technology, pre-chamber ignition can enhance ignition energy, promote flame propagation, and augment turbulence. However, this technology undoubtedly faces challenges, particularly in the context of emission regulations. Of this study, the transient characteristics of combustion and emissions in a hybrid electric vehicle (HEV) gasoline engine with active pre-chamber ignition (PCI) under the first combustion cycle of quick start are focused. The results demonstrate that the PCI engine is available on the first cycle for lean combustion, such as lambda 1.6 to 2.0, and exhibit particle number (PN) below 7×107 N/mL at the first cycle. These particles are predominantly composed of nucleation mode (NM, <50 nm) particles, with minimal accumulation mode (AM, >50 nm) particles.

Argon power cycle hydrogen engine is an internal combustion engine that employs argon instead of nitrogen of air as the working fluid, oxygen as the oxidizer, and hydrogen as the fuel. Since argon has a higher specific heat ratio than air, argon power cycle hydrogen engines have theoretically higher indicated thermal efficiencies according to the Otto cycle efficiency formula. However, argon makes the end mixture more susceptible to spontaneous combustion and thus is accompanied by a stronger knock at a lower compression ratio, thus limiting the improvement of thermal efficiency in engine operation. In order to suppress the limitation of knock on the thermal efficiency, this paper adopts a combination of experimental and simulation methods to investigate the effects of port water injection on the knock suppression and combustion characteristics of an argon power cycle hydrogen engine.

Argon Power Cycle (APC) is an innovative future potential power system for high efficiency and zero emissions, which employs an Ar-O2 mixture rather than air as the working substance. However, APC hydrogen engines face the challenge of knock suppression. Compared to hydrogen, methane has a better anti-knock capacity and thus is an excellent potential fuel for APC engines. In previous studies, the methane is injected into the intake port. Nevertheless, for lean combustion, the stratified in-cylinder mixture formed by methane direct injection has superior combustion performances. Therefore, based on a methane direct injection engine at compression ratio = 9.6 and 1000 r/min, this study experimentally investigates the effects of replacing air by an Ar-O2 mixture (79%Ar+21%O2) on thermal efficiencies, loads, and other combustion characteristics under different excess oxygen ratios. Meanwhile, the influences of varying the methane injection timing are studied.

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.

Ammonia is a new type of carbon-free fuel with low cost, clean and safe. The research and application of zero-carbon fuel internal combustion engines has become the mainstream of future development. However, there still exist problems should be solved in the application of ammonia fuel. Due to the lower flame laminar speed and higher ignition temperature, ammonia may have unstable combustion phenomena. In this work, the characteristics of ammonia combustion have been investigated, based on controllable thermal activated atmosphere burner. The ignition delay has been used to analyze the ammonia combustion characteristics. With the increase in co-flow temperature, the ignition delay of ammonia/air has an obvious decline. In order to investigate the emission characteristics of ammonia, CHEMKIN is used to validate the different chemical reaction mechanisms and analyse the ammonia emissions.

Ammonia is used as the carbon-free fuel in the engine, which is consistent with the requirements of the current national dual-carbon policy. However, the great amount of NOx in the exhaust emissions is produced after combustion of ammonia and is one kind of the most tightly controlled pollutants in the emission regulation. Nitrous Oxide (N2O) is a greenhouse gas with a very strong greenhouse effect, so that the N2O emissions needs to be paid close attention. In this paper, the CFD simulation of the N2O formation and emission characteristics during combustion is carried in the ammonia/hydrogen fueled pre-chamber jet ignition engine.

The rapid development of the automobile industry has brought energy and environmental issues that scholars are increasingly concerning about. Improving efficiency and reducing emissions are currently two hot topics in the internal combustion engine industry. Direct water injection technology (DWI) can effectively reduce the cylinder temperature, which is due to the absorption of the heat by the injecting liquid water. In addition, lower temperature in the cylinder will reduce the formation of NO. In this paper, a CFD simulation of DWI application in a lean-burning single-cylinder engine with pre-chamber jet ignition was carried out. And the engine was experimentally tested for the simulation model validation. And then the effect of DWI strategy with different injecting water mass on the combustion and emissions characteristics are analyzed. Physically, injected water not only absorbs heat but also provides heat insulation.

GDI engine has gained much popularity in vehicle market with its high thermal efficiency. However, because of higher particulate emissions, it becomes harder for GDI engines to fulfill the iteration of emission regulations in various countries. As a result, Gasoline Particulate Filter (GPF) has received more and more attention and applications. It is important to study the particulate emission and GPF performance especially for transient cycles. With a self-designed test bench with burner named Exhaust Gas Simulator, a transient control strategy to simulate the exhaust state of the WLTC cycle has been developed and achieved a fast and stable ash accumulation rate. Three levels of ash loading, in terms of 0g/L, 5g/L and 35g/L, were accumulated on respective GPF for different aging degrees with this test bench. The effect of ash loading on GPF performance was investigated.

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.

Hydrogen-fueled Argon Power Cycle engine is a novel concept for high efficiency and zero emissions, which replaces air with argon/oxygen mixtures as working fluid. However, one major challenge is severe knock caused by elevated in-cylinder temperature resulting from high specific heat ratio of Argon. A typical knock-limited compression ratio is around 5.5:1, which limits the thermal efficiency of Argon Power Cycle engines. In this article, preliminary experimental research on the effect of water direct injection at late exhaust stroke is presented at 1000 r/min with IMEP ranging from 0.3~0.6 MPa. Results show that, with temperature-reducing effect of water evaporation, knock is greatly inhibited and the engine can run normally at a higher compression ratio of 9.6:1. Water injected at the exhaust stroke minimizes its reducing effect on the specific heat ratio of the working fluid during the compression and expansion strokes.

Combustion diagnostics of highly diluted mixtures are essential for the estimation of the combustion quality, and control of combustion timing in advanced combustion systems. In this paper, a novel fast response flame detection technique based on active plasma is introduced and investigated. Different from the conventional ion current sensing used in internal combustion engines, a separate electrode gap is used in the detecting probing. Further, the detecting voltage across the electrode gap is modulated actively using a multi-coil system to be slightly below the breakdown threshold before flame arrival. Once the flame front arrives at the probe, the ions on the flame front tend to decrease the breakdown voltage threshold and trigger a breakdown event. Simultaneous electrical and optical measurements are employed to investigate the flame detecting efficacy via active plasma probing under both quiescent and flow conditions.

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%.

Advanced combustion engines dominate all automotive applications. Future high efficiency clean combustion engines can contribute significantly to sustainable transportation. Effective ignition strategies are studied to enable lean and diluted combustion under considerably high-density mixture and strong turbulences, for improving the efficiency and emissions of future combustion engines. Continuous discharge and multi-site ignition strategies have been proved to be effective to stabilize the combustion process under lean and EGR diluted conditions. Continuous discharge strategy uses a traditional sparkplug with a single spark gap and multiple ignition coil packs. The ignition coil packs operate under a specific time offset to realize a continuous discharge process with a prolonged discharge duration. Multi-site ignition strategy also uses multiple ignition coil packs.

The Argon Power Cycle engine is a novel concept for high efficiency and zero emission through the replacement of N2 by Ar. However, the higher in-cylinder temperature and pressure as by-products cause heavier knock. The anti-knock strategies, such as reducing compression ratio and retarding ignition time, offset the efficiency increased by the Argon Power Cycle. Therefore, knock control becomes the most urgent task for the Argon Power Cycle engine development. The anti-knock methods, including fuel replacement, ultra-lean combustion, high dilution combustion, and water injection, were considered. The simulated ignition delay times were used to evaluate the probability of knock. The Otto cycle, combined with chemical equilibrium, was utilized to confirm the effect on the thermal conversion efficiency and each in-cylinder thermodynamic state parameter. The results show that the ignition delay times increase by a factor of two when the Ar dilution ratio increases from 79% to 95%.

To mitigate the global warming and to develop sustainable transportation, investigations on combustion properties of carbon neutral fuels i.e., electro-fuels and bio-fuels such as propanol and butanol are essential. In the past, there were very limited researches concerning the fuel-lean combustion of those fuels, which is however a promising method for reducing the NOx emissions. Moreover, the literature chemical kinetic mechanisms have not been widely validated against the fuel-lean combustion data. Ignition delay time (IDT) is one key parameter and is widely used for validation of chemical kinetic mechanisms. The measurements of IDTs of diluted 1-propanol (nC3H7OH, CH3CH2CH2OH) and 1-butanol (nC4H9OH, CH3CH2CH2CH2OH) mixtures (with 90% bath gas (Ar+N2)) were therefore conducted in a rapid compression machine (RCM), at temperatures between 800 and 1000 K, pressures of 20 and 40 bar, under lean combustion conditions with equivalence ratios (ф) of 0.25, 0.5 and 0.9.

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.

REEV (Range-Extended Electric Vehicle) can avoid the mileage anxiety of BEV (Battery Electric Vehicle). Nevertheless, RE (Range Extender) for passenger cars prefers to use ICE (Internal Combustion Engine) with smaller displacement and lower cylinder number, which is usually with a worse vibration performance at low speeds. As RE only outputs electricity, it provides the possibility to optimize NVH (Noise, Vibration, and Harshness) of the engine by PMSM (Permanent Magnet Synchronous Motor). By real-time control, the electromagnetic torque of PMSM can track the shaft torque fluctuation during engine strokes, especially the combustion stroke. When the instability and rolling torque of RE could be suppressed, NVH performance of RE can be improved. This paper presents simulation research on speed fluctuation suppression for RE engine based on dynamic torque compensation by controlling a PMSM.