DIESEL SPRAY OF MULTI-HOLE INJECTORS WITH MICRO-HOLE UNDER ULTRA-HIGH INJECTION PRESSURE-EVAPORATING SPRAY CHARACTERISTICS

Ultra-high injection pressure and reduction of nozzle hole diameter are the development direction of future diesel engines. In this report, spray characteristics under evaporating condition are described. The results demonstrate that the increase in ambient temperature causes the spray near the nozzle to become wider. As the distance to the nozzle increases, the width of the spray tail near the nozzle tip slowly increases or remains basically unchanged. Under the evaporating condition, the spray head expands and assumes the shape of a mushroom head at the initial stage of injection. The spray of the micro-hole injector may be deflected to form a larger spray head under ultra-high injection pressure. Spray-tip penetration of injectors with different hole diameters is similar at the initial stage of injection. However, the increase in ambient temperature significantly reduces the time of similarity. The spray cone angle of micro-hole injectors under the evaporating condition is larger than that under the nonevaporating condition. But the cone angle of a large-hole injector under the nonevaporating condition is larger than that under the evaporating condition. Increases in ambient temperature only slightly affect the spray angle under different conditions. The spray evaporation results in a clear upward trend in the spray angle under 100 MPa conditions. However, under 300 MPa conditions, the spray angle does not increase because of the higher velocity. The spray evaporation effect of the micro-hole injector under a 300 MPa condition per unit mass is most favorable. The liquid length of the spray increases with the increase in the hole diameter, and a linear relationship exists between the liquid length and hole diameter of the injector. The liquid length of the spray is less affected by the injection pressure. Dos Santos' and Higgins's models can better predict the liquid length under different conditions.