Nozzle Flow and Spray Characteristics from VCO Diesel Injector Nozzles

Abstract

Imaging of the transient flow inside one of the six holes of a real size VCO-type injector incorporating a quartz window has allowed visualization of the cavitating flow in the nozzle sac and holes under realistic injection conditions. Interpretation of these two-phase nozzle flow patterns has been assisted by images obtained with both a CCD and a high-speed camera in an identical enlarged transparent injector as well as through CFD and 1-D fuel injection system calculations incorporating a bubble dynamics cavitation model and a phenomenological cavitation-induced atomisation model. Identification of the link between the internal nozzle flow and the spray characteristics has been achieved by phase Doppler measurements of the droplet size and velocities inside a constant-volume chamber for a variety of gas pressure/temperature and injection pressure conditions.