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A three-dimensional simulation was carried out for investigating effects of negative valve overlap (NVO) on gas exchange and fuel-air mixing processes in a diesel homogeneous charge compression ignition (HCCI) engine with early fuel injection. It was found that the case with longer NVO produced a stronger swirl motion and a more significant vortex below the intake valve due to the high annular jet flow through the valve curtain area during the intake stroke. However, there was not much difference in the values of swirl ratio, tumble ratio and turbulence intensity between different NVOs at the end of compression stroke. It was also seen that enlarged NVO not just increased in-cylinder temperature but also improved the temperature homogeneity. With increased NVO, there is a bigger spray shape and more droplets exist in gaps of sprays. This demonstrates that stronger turbulence intensity and higher temperature homogeneity with higher NVO improve fuel vaporization and air-fuel mixing.

In situ adaptive tabulation (ISAT) has been implemented into HCCI multidimensional modeling with detailed chemical kinetics, and the performance of ISAT was discussed. The results indicate that ISAT can reduce the computational time remarkably, and the global error can be efficiently controlled. The ISAT without growth and a reversal traverse were tested to ISAT, but they didn't influence the performance of ISAT greatly. Taking account of the character issues of chemical reactions during HCCI combustion process, an enhanced approach, the partial ISAT (PaISAT), was presented, which can significantly improve the accuracy and speed-up factor. The memory occupancy needed by ISAT was reduced based on the dynamic trimming technique.