Research on the Combustion Characteristics of Gasoline Compression Ignition(GCI) Engine Based on Quasi-Homogeneous Mixture Charge Activity Control

High-octane fuel presents significant potential for enhancing the efficient and clean combustion of small GCI engines. To achieve both efficient and stable combustion during low load scenarios, this study employs the combination of simulation and experimental methodologies. By coordinating the mixing rate and chemical reaction rate, as well as optimizing the equivalent ratio, temperature inhomogeneity and other parameters, introduces a control strategy termed ‘gasoline-air’ control coupling quasi-homogeneous mixture multi-pulse charge activity control. The research indicates that a quasi-homogeneous mixture can be formed through pilot injection of gasoline during the intake stroke, with low injection pressure can enhance charge activity and promoting clean combustion. The optimal injection timing is identified at approximately -315 CA ATDC, where appears peak value of indicated thermal efficiency. The multi-pulse charge activity control strategy can effectively control the combustion phase, heat release rate and combustion rough degree, with the injection pressure of 40 MPa and the main injection timing range of -27 CA ATDC to -24 CA ATDC yielding favorable results. Furthermore, appropriately adjusting pulse ratio and count, changing local concentration and increasing charge activity in the cylinder, contribute to improved combustion stability and enhanced indicated thermal efficiency. However, excessively changing main injection ratios can lead to rough combustion due to a reduced dilute mixture ratio and increased instantaneous heat release. At 1600 rpm and 6 bar load, with an intake pressure of 1.2 bar, the pilot injection timing at -315 CA ATDC, and the main injection timing at -27 CA ATDC, using a quasi-homogeneous charge activity control strategy, the indicated thermal efficiency reaches as high as 52.6%, and the NOx emission is 0.25 g/kWh, meeting the clean combustion standards.