CFD simulations of diesel spray tip penetration with multiple injections and with engine compression ratios up to 100:1

Abstract

A diesel spray tip penetration was simulated with CFD by varying the compression ratio from the conventional compression ratio of a diesel engine, 18:1, to an ultra-high compression ratio of 100:1. The gas densities of the spray chambers for the compression ratios of 18:1 and 100:1 were 17.97 and 74.8kg/m3, respectively. The spray tip penetration was CFD simulated by adopting both the ‘Gas jet spray model’, and ‘Normal gas jet profile model with breakup length formula’ (NGJBL model) into the KIVA-3V code. The spray tip penetration was CFD simulated for various spray patterns, such as single injection, pilot injection and split injection. The CFD simulation of the spray tip penetration with an 18:1 compression ratio was compared with a previous study with identical experimental conditions and showed that the ‘Gas jet spray model’ over predicted. The CFD simulation results with the ‘KIVA-3V Standard spray model’ and the NGJBL model were generally in good agreement with the experimental data. The spray tip penetration was CFD simulated with the NGJBL model with step-by-step increased compression ratio. The spray tip penetration rapidly decreased for the range of compression ratio of 18:1–45:1 as the compression ratio increases and the spray tip penetration did not change much with increasing the compression ratios in the range of 60:1–100:1. The CFD simulation results of the spray tip penetration, with respect to varying compression ratios, were generally in agreement with previous experimental studies.