Investigation of the Cavitation in High Pressure Diesel Injection Nozzles

Laser light sheet and shadowgraphy techniques have been applied to investigate cavitation phenomena in the spray hole of Diesel injection nozzles. The nozzles were operated on a test-bench based on a Common Rail injection system. Rail pressures up to 50 MPa were used. The diesel test oil was injected into a chamber which could be pressurized up to 8 MPa. The local position and range of cavitation films, lying between the flow and the nozzle wall, as well as single bubbles could be observed at different instants of the injection process. The pictures of the light sheet experiment were compared with photographs taken by the shadowgraphy technique under the same injection conditions. Cavitation number estimates were obtained by direct measurements of nozzle sac pressures.