Influence of ambient flow conditions on the droplet atomization characteristics of dimethyl ether (DME)

This paper describes the effects of ambient flow conditions on the droplet atomization characteristics of dimethyl ether (DME) both experimentally and numerically. In this investigation, the droplet atomization of DME fuel affected by ambient flow conditions was studied in terms of droplet mean size and detected droplet percentage under elevated ambient pressures and temperatures. In order to predict the DME spray atomization, the hybrid breakup model combined with KH-RT (Kelvin-Helmholtz and Rayleigh-Taylor) and KH-DDB (Kelvin-Helmholtz and Drop Deformation Breakup) models was applied in this study. It was revealed that the spray arrival time of DME fuel under a high ambient pressure increased in accordance with the increase in ambient pressure in the spray chamber. It can be seen that more small droplets are distributed at high ambient flow pressure conditions than at atmospheric conditions. This is a consequence of enhanced atomization of DME fuel. On the other hand, when the ambient pressure increases to 2 MPa, the Sauter mean diameter (SMD) increases only slightly compared with that at I MPa of pressure. The SMD value of droplets is increased as ambient temperature is increased. Under the high temperature condition in the chamber, the small droplets of DME fuel evaporate quickly and mix with the ambient air. As a result, it promotes the air-fuel mixing in a combustion chamber. (C) 2008 Elsevier Ltd. Ail rights reserved.