Experiment and simulation analysis of the effects of different asynchronous variable intake valve phase differences on the in-cylinder flow, combustion and performance characteristics of high compression ratio turbocharged enhanced Miller cycle engine

In this study, a novel asynchronous variable intake valve phase Miller cycle (AVIVPMC) was proposed and applied to a high geometric compression ratio (GCR) turbocharged GDI engine. Based on the experimental data, the 3D computational fluid dynamics (CFD) model was established and calibrated under the operating condition of 2000 r/min and 8 bar (BMEP) to further analyze the energy-saving mechanism of AVIVPMC. Thus, the effects of different asynchronous intake valve phase difference (AIVPD) on in-cylinder flow characteristics, combustion characteristics and performance characteristics of AVIVPMC engine were studied. The results showed that the AVIVPMC could effectively reduce pumping loss and the BSFC of the AVIVPMC engine was reduced by more than 5 % under most test loads. The introduction of AVIVPMC effectively increased the in-cylinder swirl ratio, and the swirl ratio increased as the AIVPD increased. The peak of the in-cylinder swirl ratio could reach about 4.5. However, the larger swirl ratio weakened the in-cylinder tumble ratio and reduced the in-cylinder turbulent kinetic energy, resulting in the decrease of combustion efficiency. The reduction of the ECR of the AVIVPMC engine enhanced the knock resistance and significantly increased the thermal conversion efficiency.