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To model the spray atomization for diesel HCCI engines, three breakup models including the Taylor Analogy Breakup (TAB), Cascade Atomization and Drop Breakup (CAB) and Kelvin-Helmholtz Rayleigh-Taylor (KH-RT) were evaluated. Based on the experimental results from constant volume, the prediction accuracy of three breakup models was assessed in terms of spray penetration, droplet diameter, droplet velocity and vapor distribution. The results indicate that the mean droplet diameters are significantly underestimated by the TAB model, and the CAB model shows the best performance in the droplet diameter and velocity distributions, but predicts delayed vapor distribution. The KH-RT model shows good predictions in all aspects. By using the KH-RT model, the influence of different injection strategies, including injection timing, spray angle, spray pressure, nozzle hole diameter and split injection, on the mixture preparation process for diesel HCCI engines were investigated.

The multi-zone model has been attracting growing attention as an efficient and accurate numerical model for homogeneous charge compression ignition (HCCI) combustion simulations. In this paper, a comparative study was carried out to clarify the effect of various sub-models on the prediction capability of the multi-zone model. The influences of the distribution of zones, heat transfer from the wall, mass and heat exchange between zones and boundary layer thickness on HCCI combustion and emissions were discussed based on the experimental data. The results indicate dividing the colder region into more zones can improve the emissions prediction, however, more zones in the hotter region has little effect on the predictions. The improved Woschni model significantly improves the prediction of heat transfer.

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.