Effects of pre-injection parameters on spray characteristics of high-pressure common rail diesel engines

A verified hydrodynamic spray model was used to investigate the effects of multiple injection strategies on fuel bundle development and atomization characteristics of diesel fuel under typical conditions of direct-injection, turbocharged, and high-speed automotive diesel engines. Emphasis is placed on the effect of injecting a small amount of pre-injection fuel prior to the main injection on the spray development process. In addition, the effect and degree of influence of pre/main-injection interval time and pre-injection fuel ratio on spray macro- and micro-parameters in the two-injection strategies. The results show that at the end of the injection process, as the pre/main-injection interval time increases, the spray gas phase penetration distance increases, the spray width and the spray volume of the high-temperature region decrease, and the fuel concentration in the vicinity of the nozzle is in a decreasing trend. As the pre-injection ratio increases, the spray gas phase penetration distance decreases, the spray width, the spray volume of the high-temperature region increases, the spray volume between the fuel equivalence ratio of 0.8-1.2 decreases, and the fuel concentration at the front end of the spray tends to increase. The effect of the proportion of pre-injection fuel on spray width, spray volume of the high-temperature region, and spray volume between the fuel equivalence ratio of 0.8-1.2 was 4.88, 4.56, and 11.5 times that of changing the pre/main-injection interval time, respectively. The research provides a basis for optimizing the injection strategy and applying multiple injection technology in high-pressure common rail diesel engines.