Effects of Hole Diameter and Injection Pressure on Fuel Spray and Its Evaporation Characteristics of Multi-Hole Nozzle for Diesel Engine 2017-01-2305

The performance of a diesel engine largely depends on the spray behavior and mixture formation. Nozzle configurations and operating conditions are important factors that influence spray development. Using numerical and experimental methods, this study focused on the spray development of multi-hole nozzles under non-evaporating and evaporating conditions to compare the influence of nozzle hole diameter and injection pressure on spray characteristics. High-speed video observation was employed to study the properties of spray development under the non-evaporating condition, while the Laser Absorption Scattering technique was used in the observation and quantitative analysis of evaporating spray characteristics in the evaporating condition. In addition, computational fluid dynamics study results published previously [1] were correlated with the current experimental results to provide more detailed explanations about the mechanism of the characteristics of spray behavior. As for the effects of hole diameter, the evaporation ratio increased when the nozzle with smaller hole diameter was used at the initial injection phase. However, especially after injection, the evaporation ratio increased with increasing nozzle hole diameter because of the shorter injection duration. With regard to the effect of injection pressure, high injection pressure accelerated the internal flow that promotes the high cavitation level inside the nozzle. High injection pressure also provides high momentum, which prolongs the spray tip penetration. As a result, the evaporation ratio increases with the increase in injection pressure. The combined effects of nozzle hole diameter and injection pressure under similar fuel injection rates were investigated in the last section. The results show the distinct features for each condition although they have similar injection rate curves.