Abstract
This paper reports the injection of a supersonic diesel fuel jet by a compact gas gun. The diesel fuel was contained in a titanium alloy nozzle and sealed by a 1-mm-thick rubber diaphragm. A high-speed polyethylene projectile hit a brass piston located at the back end of the nozzle, and consequently, the fuel was pushed through a small nozzle hole to form a supersonic jet in air. The supersonic jets were visualized by double-exposure holographic interferometry. The influences of the nozzle diameter D, the ratio of nozzle length to nozzle diameter L/D, and injection volume on the diesel fuel injection were examined separately. A pressure chamber was designed for measuring the injection pressure. It was found that the rubber sealing diaphragm did not affect the amplitude and width of the pressure pulse caused by compression of the brass piston. The interaction between a supersonic diesel fuel jet and a solid wall was also studied. Photographs show that the reflection of the precursor shock wave of the supersonic jet from the wall surface may play an important role in mixing diesel fuel with surrounding gas, and producing a high concentration of fuel vapor.
