Spray and atomization characteristics of isobutene blended DME fuels

This paper investigates the macroscopic and microscopic characteristics of DME(dimethyl ether)/isobutene blended fuel using a spray visualization and droplet particle analyzing system. In this study, the spray characteristics of DME/isobutene blends were investigated with regard to spray injection rate, spray tip penetration, spray cone angle, and the development of spray images at various blending ratios of isobutene fuel. In addition, the size distribution of DME/isobutene blended fuels and the velocity distribution of blended fuels were conducted and compared to those of conventional diesel fuel. The results showed that DME fuel has a higher injection rate peak than those of the DME/isobutene blends. The spray tip penetration increased with an increase in the injection pressure; however, the increasing rate of the spray penetration decreased with an increase in injection pressure. The spray cone angle at a 60 MPa injection pressure was larger than that at 30 MPa of injection pressure. The effect of ambient pressure on the spray cone angle according to the variation in ambient pressure showed that the spray cone angle is wider at the beginning of the fuel injection, and it converges to a similar and constant distribution. The droplet size of DME fuel showed the smallest Sauter mean diameter among the DME/isobutene blending fuels due to the excellent evaporation characteristics compared to those of blended fuels. The droplet size distributions of the test fuels were divided into two patterns: DME and the other three DME/isobutene blended fuels.