Hole Geometrical Effect on Internal Flow, Fuel Atomization and Spray Evaporation of Multi-Hole Nozzle for Diesel Engine 2017-01-0860

With the aim of improving engine performance, recent trend of fuel injection nozzle design followed by engineers and researchers is focusing on more efficient fuel break up, atomization, and fuel evaporation. Therefore, it is crucial to characterize the effect of nozzle geometric design on fuel internal flow dynamics and the consequent fuel-air mixture properties. In this study, the internal flow and spray characteristics generated by the practical multi-hole (10 holes) nozzles with different nozzle hole length and hole diameter were investigated in conjunction with a series of computational and experimental methods. Specifically, the Computational Fluid Dynamics (CFD) commercial code was used to predict the internal flow variation inside different nozzle configurations, and the high-speed video observation method was applied to visualize the spray evolution processes under non-evaporating conditions. Moreover, the Laser Absorption Scattering (LAS) method was implemented to explore the spray evaporation characteristics. The different nozzle internal flow properties summarized from the computational results could be used to give a comprehensive explanation for the mechanism behind the spray behaviors observed in the experiments. Furthermore, the nozzle geometrical design effect was correlated with the numerical and experimental results under the evaporating and non-evaporation conditions. It indicated that the hole geometry can alter the dynamic internal flow, liquid jet break up, spray propagation, and the ambient gas entrainment, simultaneously. Moreover, two of the most important factors, hole diameter and hole length, can exert different effect on the spray break up and evaporation process. For the current experiments, an appropriate ratio of nozzle hole length to diameter is found and suggested concerning the fuel break up and evaporating characteristics. When pursuing the optimum nozzle geometrical design, the effect of hole length and hole diameter should be considered from a comprehensive view.