An Optical Study the Spray Characteristics of Dimethyl Ether in a Constant Volume Combustion Chamber

As a typical carbon-neutral fuel, the spray properties of DME were measured in a constant-volume combustion chamber by means of Schlieren method. The injection pressure was set from 60 to 100 MPa. Three spray states (non-flash boiling, transition boiling, and flare flash boiling) were studied at the 0.2 and 4 MPa environmental pressure. The results show that the gas phase spray tip penetration (STP) and spray projected area (SPA) of the three different spray states increased with injection pressure elevated. However, the liquid STP and SPA almost remain in a certain range. Besides, with decreasing ambient pressure, the liquid DME spray changed from a smooth plume to a fine needle, but the gas phase profiles were smooth. In addition, spray resistance phenomenon in DME is observed around 0.3 ms into the initial injection phase. After the spray resistance phenomenon disappears, both the gas phase STP and SPA increase with decreasing ambient pressure. Therefore, flare flash boiling and high injection pressure are conducive to promoting the atomization of DME spray.