Study on the Common Rail Type Injector Nozzle Design Based on the Nozzle Flow Model

In this paper, a nozzle flow model was used to design an injector nozzle and obtain initial spray conditions for the dimethyl ether (DME) common rail-injection system. In order to deliver the same amount of energy as that provided by diesel at a low injection pressure of 50 MPa, the injector for DME needs nozzle holes with larger diameters and a higher SAC volume for the same injection duration. In addition, the needle lift and needle seat diameter should be increased to maintain a minimum flow area ratio. Although the vapour pressure and maximum injection pressure of DME are lower than those of diesel, the nozzle in a DME system showed higher discharge coefficients and effective nozzle exit diameters for the same injection duration owing to low kinematic viscosity. However, because the maximum injection pressure in DME is lower than that with diesel, and the length of the cavitation region is narrower.