Effect of Intake Conditions and Nozzle Geometry on Spray Characteristics of Group-Hole Nozzle

The group-hole nozzle concept is proposed to meet the requirement of nozzle hole minimization and reduce the negative impact of poor spatial spray distributions. However, there are limited researches on the effects of intake conditions and nozzle geometry on spray characteristics of the group-hole nozzle. Therefore, in this study, an accurate spray model coupled with the internal cavitating flow was established and computational fluid dynamics (CFD) simulations were done to study the effects of intake conditions and nozzle geometry on spray characteristics of the group-hole nozzle. Experimental data obtained using high-speed digital camera on the high-pressure common rail injection system was used to validate the numerical model. Effects of intake conditions (injection pressure and temperature) and nozzle geometry (orifice entrance curvature radius and nozzle length) on the flow and spray characteristics of the group-hole nozzle were studied numerically. The differences in Sauter mean diameter (SMD), penetration length and fuel evaporation mass between single-hole nozzle and group-hole nozzle under different nozzle geometry were also discussed. It was found that the atomization performance of the group-hole nozzle was better than that of the single-hole nozzle under same intake conditions, and the atomization effect of the short nozzle was better than that of the long nozzle. With increase in the orifice entrance curvature radius, the average velocity and turbulent kinetic energy of the fuel increased, which was conducive to improving the injection rate and flow coefficient of the nozzle. Meanwhile, the penetration length and SMD value rose, while evaporation mass dropped. When the ratio of the orifice entrance curvature radius (R) to the diameter of injection hole (D) was 0.12, the spray characteristics reached a constant state due to elimination of cavitation. Conclusions were made based on these. This study is expected to be a guide for the design of the group-hole nozzle. © 2023, Tech Science Press. All rights reserved.