Atomization characteristics of dimethyl ether fuel as an alternative fuel injected through a common-rail injection system

The objective of this work is to analyze the macroscopic development and atomization characteristics of dimethyl ether (DME) and diesel fuel spray injected through a common-rail injection system in a diesel engine. To investigate the spray behavior of DME fuel, the macroscopic and microscopic spray characteristics of DME were analyzed in terms of spray development, spray tip penetration, spray cone angle, impingement timing, mean droplet size, and the mean velocity. The process of macroscopic DME spray development was visualized according to various injection parameters such as injection duration, ambient and injection pressures, ambient temperature, and combustion chamber geometry via a spray visualization system composed of an neodymium-doped yttrium aluminum garnet (Nd:YAG) laser and an intensified charge coupled device (ICCD) camera. DME fuel atomization characteristics in a high-pressure spray chamber such as axial mean velocity and droplet size distribution were measured with a phase Doppler particle analyzing (PDPA) system. It was revealed that the DME spray has a shorter spray tip penetration and a wider spray cone angle than diesel fuel under identical test conditions. The surface area also was smaller, and the axial direction spray centroid of DME was higher than that of diesel fuel. In the case of incylinder spray, the DME spray developed slower and disappeared faster after the start of the injection. The comparison of spray profiles in both fuels shows that diesel fuel has a larger Sauter mean diameter (SMD) value than DME.