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Due to increasingly strict global emission regulations and energy conservation policies, gasoline engines are facing significant challenges. Achieving high efficiency and ultra-low emissions in gasoline engines has become a critical technical challenge that requires attention. Pre-chamber (PC) Turbulent Jet Ignition (TJI) is a highly promising technology for improving thermal efficiency and reducing emissions in gasoline engines. This study employs a three-dimensional flow simulation analysis combined with a detailed chemical reaction mechanism. The investigation is based on eight distinct passive PC structural configurations. The effects of various structural parameters, including the orifice number (ON), orifice axis angle (OAA), orifice diameter (OD), and volume ratio (VR), on the in-cylinder combustion process and emission characteristics are investigated, in which the formation of the fire nucleus and the propagation of the flame are intensively involved. The investigation is conducted under equivalence ratio working condition. Among these, the ITE of the best configuration is relatively 5.46% higher than the baseline engine. The combustion duration decreased by 55.95% to 7.4 °CA compared to the baseline engine, while particulate soot emissions also decreased by 51.22%.

By establishing oxy-fuel combustion, direct water injection and waste heat recovery within conventional diesel engine, the compression ignition-internal combustion Rankine cycle (CI-ICRC) concept can be realized. It is capable of achieving ultra-high thermal efficiency and low emission. There have been studies on DWI timing in homogeneous charge compression ignition (HCCI) mode, but no systematic researches within CI-ICRC. Therefore, a prototype CI-ICRC engine is established in this work, the cycle performance (including in-cylinder pressure, heat release rate, brake thermal efficiency, etc.) and emission characteristics under different DWI timings are compared. The prototype engine was operated at 800 r/min. DWI temperature, pressure and duration are kept constant at 433 K, 35 MPa and 2 ms. The results indicate that DWI before combustion is more effective in reducing combustion intensity. The optimum DWI timing within this study is 320℃A, while the brake thermal efficiency (BTE) reaches the maximum of 46.6 % with a coefficient of variation close to 1 %. NOx and soot emissions are optimized but CO and HC emissions slightly increased with the utilization of DWI. The experimental results can provide guidance for future CI-ICRC engine optimization, and can also be utilized in providing reference information for DWI utilization within other novel internal combustion engine (ICE) concepts.

Compression ignition-internal combustion Rankine cycle (CI-ICRC) concept implement oxy-fuel combustion, direct water injection (DWI) and waster heat recovery into traditional diesel cycle to realize ultra-high thermal efficiency and low emission powertrain. As indicated by ICRC concept, the DWI process show critical impact on its combustion process and thermal efficiency. This paper dedicated in investigating the effect of different DWI temperature on cycle performance and thermal efficiency within prototype CI-ICRC engine, in order to do so, independent DWI system, O2/CO2 intake system and reconfigurable electronic controller is established. Combustion characteristics including in-cylinder pressure, heat release rate, combustion stability, brake thermal efficiency are experimentally investigated. The cycle performance and thermal efficiency are proved to be optimized under elevated DWI temperature, an optimum 46.6% brake thermal efficiency is achieved, while the coefficient of variation remains around 1%. The NOX and soot emissions are both reduced under DWI utilization, the mechanism of soot reduction is highly related to thermolysis of water or carbon-water reactions which further chemical kinetic analysis is needed. The result of this study provides fundamental information for future CI-ICRC engine optimization, and can also be utilized in providing reference guidance for DWI implementation within modern internal combustion engines.