Numerical study on the effect of injection pressure on high-pressure diesel spray

This paper analyses the effect of injection pressures on spray and flame structures under high-pressure diesel spray conditions using a three-dimensional Reynolds-Average Navier-Stokes (RANS) model. The simulations are conducted using three kinetic mechanisms known as Luo (106 species), Cai (57 species) and Yao (54 species). Tabulation and Dynamic Adaptive Chemistry (TDAC) solver is adopted to reduce the computational cost. The reacting results obtained using the Luo kinetic mechanism demonstrate the best agreement with the experiment. The Cai and Yao chemistry models overpredict and underpredict the ignition delay time respectively, whereas both mechanisms overpredict the flame lift-off length, particularly at higher injection pressures. It is found that the error for the ignition delay time is larger at higher injection pressures while the opposite is true for the flame lift-off length. The results reveal that at lower injection rates, the cool flame, represented by the CH₂O, occurs at richer mixture closer to the nozzle. On the other hand, the heat release rate is lower while the CO emission is higher. Detailed analysis on scalar fields shows that the Cai and Yao mechanisms lead to more consistent results in capturing the temperature field in terms of high-temperature reaction zone while Yao and Luo mechanisms result in a more consistent trend in producing the C₂H₂ species.