Evaluation of impingement effects on high-power diesel engine mixing process with an optimized stochastic combustion model

Abstract

• The mixing-controlled combustion can be modelled by a stochastic combustion model. • The impingement is evaluated by a volume ratio between squish part and total spray. • The modeling is classified into different types according to the impinging location. • The spray impingement significantly enhances the mixing rate. Spray impingement has been proved to have remarkable influence on the mixing process, and particularly for high-power diesel engines, where the dominant diffusion combustion is mixing-controlled. Therefore, in this paper, the stochastic combustion model, which has the capability to indicate the heterogeneity of the fuel–air mixing, was optimized to account for the influence of spray impingement. The combustion chamber was divided into squish region and non-squish region, and by judging the location of the spray/wall impingement, the spray was correspondingly divided into squish part and bowl part. After that, a parameter that was defined as the volume ratio between squish part and the total spray was introduced to evaluate the influence of impingement on spray mixing rate. Finally, the optimized stochastic combustion model was validated by a single-cylinder high-power-density diesel engine to have the ability to estimate the influence of spray impingement on the mixing rate of mixture and the performance of diesel combustion with a pretty good accuracy, and the results showed that, spray impingement significantly enhanced the fuel–air mixing rate, contributed to leaner and more homogenous mixture and hence optimizing the combustion.