Experimental investigation on flashing water jet and resulting shock wave

Abstract

This paper presents an experimental study on spray flash evaporation occurring in a superheated water jet injected through a short nozzle into a vacuum chamber. The study presents shock waves as one of significant consequences that can be produced by flash evaporation, which can be utilize for creating useful compression. The experimental study is carried out with the liquid water initially at a pressure of 101325 Pa, and a temperature ranging from 40 °C to 100 °C, and the backpressure (vacuum pressure) ranging from 4000 Pa to 10000 Pa. The experimental set-up includes Schlieren technique utilizing a high-speed camera to capture images of the flashing and the generated shock wave. The Schlieren photographs were mathematically filtered using the Image Processing and Analysis in Java to show the induced shock wave structure. The results show that increasing the initial water temperature accelerates and enhances the flash evaporation. Full flashing generating a shock wave takes place at high initial liquid temperature and low backpressure.