Characteristics of Diesel Spray with Unsteady and Higher Injection Pressure Using a Rapid Compression Machine

This paper presents the characteristics of diesel spray with higher and unsteady injection pressure under an elevated pressure and temperature condition. For this purpose, a pneumatically actuated rapid-compression machine was developed, which has 120 mm bore combustion chamber. A Bosch type injection system was used and can realize the maximum injection pressure about 160 MPa. By using high-speed photography, the spray-tip penetration and the spray angle were measured. Under the non-evaporating condition, the penetrations of higher and normal injection pressure are almost the same, whereas, under the evaporating condition, those penetrations are not the same. Thus, the penetration of the normal injection pressure is affected by the ambient temperature, while that of the higher injection pressure is little affected by the evaporation. The same tendency was observed in the behavior of spray angle development. It is also shown that fairly large eddies start to be generated at a certain stage of spray development and the spray formation process is affected by the growth and dissipation of those eddies.