A numerical study based on the Box Behnken design(BBD) was made to analyze the Kelvin-Helmholtz & Rayleigh-Taylor(KH-RT) model constants in the simulation of evaporating diesel spray mixture. The mixing process of evaporating diesel spray was recorded by high-speed shadowgraph technique during fuel injection in a constant-volume vessel with the ambient temperature of 900 K

ambient density of 15 kg/m3 and injection pressure of 120 MPa. The simulated liquid- and vapor-phase penetrations were compared with the experimental results. According to the relative difference theory

the response surface method was adopted to evaluate the influence of each model constant on evaporating diesel spray mixture development. The results show that the breakup time constant plays a dominant role. Furthermore

an optimized combination of the KH-RT model constants was obtained and validated for predicting the evaporating diesel spray.