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In this study, the internal nozzle flow and macroscopic spray characteristics of a kind of wide distillation fuel (WDF) - kerosene were investigated both with numerical and experimental approaches. Simulation results indicate that compared with diesel fuel, kerosene cavitates more due to higher turbulent kinetic energy as a result of lower viscosity. The results from experiment indicate that under lower charge density, the spray penetration for kerosene is obviously shorter than that for diesel, especially for the lower injection pressure. This is because lower fuel viscosity results in a reduction in the size of the spray droplets, leading to lower momentum. However the spray angle of kerosene is larger compared with diesel due to stronger turbulence in the nozzle flow caused by increased cavitation for kerosene, which also accords well with the simulation results.

Gasoline engines suffer low thermal efficiency and diesel engines have the emission problem of the trade-off between NOx and soot emissions. Homogeneous Charge Induced Ignition (HCII) is introduced using a port injection of gasoline to form a homogeneous charge and using a direct injection of diesel fuel to ignite. HCII has the potential to achieve high thermal efficiency and low emission combustion. However, HCII combustion mode still has problems of high THC emissions at low load and high pressure rise rate at high load. In order to improve the gasoline reactivity and reduce THC emissions, double injection of diesel was applied in HCII mode. In order to reduce peak pressure rise rate (PPRR), a two-staged high-temperature heat release is achieved at suitable engine condition. The effects of HCII mode on combustion and emission characteristics are studied in a light-duty engine.

In this study, experimental and simulation investigations on the roles of charge density (ρtdc), temperature (Τtdc) at the top dead center and oxygen concentration (φO2) on the combustion paths, emissions and thermal efficiency of a high load operation diesel engine were conducted. Experimental engine was a modified single-cylinder engine equipped with variable mechanisms of boost, exhaust gas recirculation (EGR) and intake valve closing timing (IVCT) to regulate the Ptdc, φO2 and Τtdc. Simulations of engine combustion processes were performed with an ECFM-3Z combustion model. The results revealed that higher Ptdc, leading to lower overall fuel/oxygen equivalence ratio (Φm), enhanced the rate of mixing and chemical reaction and benefited improvement of the thermal efficiency.

In this study, Partially Premixed Combustion (PPC) on a modified heavy-duty diesel engine was realized by hybrid combustion control strategy with flexible fuel injection timing, injection rate pattern modulation and high ratio of exhaust gas recirculation (EGR) at different engine loads. It features with different degrees of fuel/air mixture stratifications. The very low soot emissions of the experiments called for further understanding on soot formation mechanism so that to promote the capability of prediction. A new soot model was developed with highlight in effects of surface activity on soot growth for soot formation prediction in partially premixed combustion diesel engine. According to previous results from literatures on the importance of acetylene as growth specie of PAH and soot surface growth, a gas-phase reduced kinetic model of acetylene formation was developed and integrated into the new soot model.

A Homogeneous charge induced ignition (HCII) combustion, realized by in-cylinder fuel blending of gasoline and diesel fuel, was developed and carefully optimized, both on a single cylinder and a multi-cylinder light-duty diesel engines, for high thermal efficiency and near zero emissions in a wide engine-operation range up to IMEP of 1 MPa. The effects of mixing and chemical parameters of HCII combustion, which can be controlled by production-viable hard-ware using conventional gasoline and diesel fuel, include injection timing of diesel fuel, injection rate pattern of diesel fuel (such as split injection), the gasoline/diesel ratio, boost pressure and exhaust gas recirculation (EGR). Based on a single cylinder engine, the experimental result shows that the interaction of the mentioned control parameters plays decisive role in determination of exhaust emissions and thermal efficiency.

The Premixed Charge Compression Ignition (PCCI) engine has the potential to reduce soot and NOx emissions while maintaining high thermal efficiency at part load conditions. However, several technical barriers must be overcome. Notably ways must be found to control ignition timing, expand its limited operation range and limit the rate of heat release. In this paper, comparing with single fuel injection, the superiority of multiple-pulse fuel injection in extending engine load, improve emissions and thermal efficiency trade-off using high exhaust gas recirculation (EGR) and boost in diesel PCCI combustion is studied by engine experiments and simulation study. It was found that EGR can delay the start of hot temperature reactions, reduce the reaction speed to avoid knock combustion in high load, is a very useful method to expand high load limit of PCCI. EGR can reduce the NOx emission to a very small value in PCCI.