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. It is found that optimization of the spray target by adjusting injection timing and spray angle can help achieve more homogeneous mixture. Higher spray pressure and smaller nozzle hole diameter lead to better fuel evaporization.