Influence of inlet pressure on cavitation flow in diesel nozzle

Abstract

This paper presents an investigation combining both experiment and simulation on the sole impacts of the injection pressure pin on the inner cavitation process, and the effects of the cavitation on the flow capacity of the nozzle. An optical nozzle is designed based on the similarity principle of amplification in an equal proportion, and both the structure and the cavitation number are similar to the baseline nozzle. A numerical model is built to analyse the details of the inner flow. The results show that cavitation occurs as pin increases, and a bubble ring forms. The total flow process is divided into three periods: the no-cavitation, the cavitation developing and the stable cavitation periods. During the no-cavitation period, no bubbles occur, and the discharge coefficient Cd is a constant and determined by the nozzle structure. During the cavitation developing period, when pin rises, the area of the bubble ring increases, but Cd decreases and is governed by f the cavitation number CN and the cavitation area coefficient KA. During the stable cavitation period, at the inlet the bubble ring reaches the maximum then becomes stable; Cd is determined only by CN, and infinitely close to a constant as pin increases.