DEVELOPMENT OF A NEW SPRAY/WALL INTERACTION MODEL FOR DIESEL SPRAY UNDER PCCI-ENGINE RELEVANT CONDITIONS

A new spray/wall interaction model was developed with special emphasis on the premixed charge compression ignition (PCCI) engine-relevant conditions, i.e., high injection pressure and intermediate-to-high backpressure. The new model distinguishes between dry wall and wetted wall for a description of the complicated spray/wall interaction process. The dry wall impingement regimes include deposition and splash, whereas the wetted wall regimes consist of stick, rebound, spread, and splash. The regime transition thresholds of splash are determined based on recent experimental observations, which can account for the wide ranges of conditions related to engines. By using an updated log-normal distribution function, the sizes of the secondary droplets are determined in the improved model, which is more suitable to describe the atomization process of the secondary droplets formed by splash. Moreover, the velocities of the secondary droplets are determined by a Nukiyama-Tanasawa distribution function derived from the experimental measurements, and the ejection angle of the secondary droplet is assumed to be in the interval (2 degrees, 30 degrees) uniformly, which is reasonable for high injection pressure. In order to validate the new spray/wall interaction model, comparisons of the predictions from the present model with the experimental measurements and predictions from a previous spray/wall interaction model were conducted. The results indicate that the numerical predictions from the new model illustrate better agreements with the experimental data than those of the previous model, especially in the case with high injection pressure under PCCI-engine relevant conditions.