An investigation on the spray characteristics of DME with variation of ambient pressure using the common rail fuel injection system

Abstract

We investigated the DME spray characteristics about varied ambient pressure and fuel injection pressure using the common rail fuel injection system when the nozzle holes diameter is varied. The common rail fuel injection system and fuel cooling system were used since DME has compressibility and vaporization at atmospheric temperature. The fuel injection quantity and spray characteristics were measured. The spray was analyzed for spray shape, penetration length, and spray angle at the six nozzle holes. There are two types of injectors: 0.166 mm diameter and 0.250 mm diameter. The ambient pressure, which was based on gage pressure, was 0, 2.5, and 5 MPa. The fuel injection pressure was varied by 5 MPa from 35 to 70 MPa. By comparing with the common injector, using the converted injector it was shown that the DME injection quantity was increased 127% but it didn’t have the same low heating value. Both the common and converted injectors had symmetric spray shapes. In case of converted injector, there were asymmetrical spray shapes until 1.2 ms, but after 1.2 ms the spray shapes were symmetric. Also, the converted injector had shorter penetration length and wider spray angle than the common injector.