Microscopic Spray Characteristics of Dimethyl Ether and Diesel in Ambient Conditions

Abstract

A spray study is essential to understand the combustion and emissions from internal combustion engines (ICEs). It supports engine performance optimization and tailpipe emission reduction. The characteristics of the fuel spray determine the fuel–air mixing and essential requirements for efficient combustion. Thus, fuel spray characterization is necessary to understand the spray atomization and droplet velocity. Fuel properties, ambient conditions, fuel injection pressure, and injector nozzle design influence the spray characteristics. This experimental study used a mechanical injector to perform a comparative analysis of the microscopic spray characterization for dimethyl ether (DME) and diesel at fixed injection pressure and ambient conditions. Spray characterization was performed inside a constant volume spray chamber (CVSC) to assess spray droplet velocity and size distributions using a phase Doppler interferometer (PDI). Results showed that the DME spray droplet sizes were smaller than diesel due to differences in test fuel properties such as surface tension and viscosity. The number of smaller droplets in DME spray surpassed the numbers for diesel. This study showed that DME spray has exceptional evaporation/atomization properties, enhancing the fuel–air mixture's homogeneity, which improves the combustion, performance, and emissions of DME-fueled engines.