Diesel spray and combustion of multi-hole injectors with micro-hole under ultra-high injection pressure – Non-evaporating spray characteristics

Abstract

Increasing the injection pressure and reducing the nozzle hole diameters can increase the thermal efficiency of diesel engines (DI). To understand the spray characteristics under ultra-high injection pressure, the spray characteristics of multi-hole injectors with different diameters were investigated under different injection pressures. The results show that the injector with a larger hole diameter has a larger injection delay and a longer injection rate rise and fall time. The injection pressure has a small effect on the injection delay. As the injection pressure increases, the injection rate rise and fall time decreases. Increasing the injection pressure and the hole diameter increases the instability of the spray. The penetration of the injectors with different hole diameters is similar in the initial stage of injection. The penetration increased with the increase of the injection pressure. However, the effect of the high injection pressure on the increase of the penetration becomes weak. The injectors with a larger nozzle hole diameter displayed a larger penetration, spray angle, spray cone angle, and spray area. The micro-hole injector under the ultra-high injection pressure, the expansion of the middle of the spray caused a larger spray angle and spray area. A larger nozzle hole diameter and injection pressure promotes an increase in the gas mass rate. But the injector with the micro-hole diameter has a better ṀA/ṀF ratio and a lower average spray equivalent ratio under ultra-high injection pressure. Naber and Siebers’ penetration model and Inagaki and Mizuta's spray angle model with modified parameters showed the better prediction effect under all experimental conditions.