Effect of Cavitation inside Injection Nozzle on Spray Characteristics for Direct Injection (1st Report : Pressure Measurement inside the Nozzle Hole for Various Injection Pressure and Saturated Vapour Pressure of the Test Fuel)

Abstract

The objective of this study is to understand the effect of cavitation inside the injection nozzle on spray atomization for various nozzle geometries and injection conditions. In this paper, pressure measurement and observation of flow pattern including cavitation inside the nozzle hole were carried out for various injection conditions and saturated vapor pressure of test fuel using by transparent nozzle which was made of acrylic and magnified 25 times. As results of these experiments, with increase in saturated vapor pressure of test fuel under the same injection pressure, cavitation develops toward the downstream of the injection nozzle hole similar to the conditions of high injection pressure with the same test fuel. The strong relationship between pressure distribution and cavitation region inside the nozzle was obtained for both experimental parameters. In addition, there was not much difference in patterns of pressure distribution and liquid jet between both experimental parameters under the same cavitation number. It is concluded that the cavitation region, pressure distribution inside the nozzle and width of liquid jet are able to be arranged by use of cavitation number.