Introducing of the propagation criterion and investigation of that for near vacuum chamber pressures for multi hole gasoline direct injector spray

with developing of optical technologies, using of different imaging methods to study various properties of gasoline direct injection spray is under development. Scope of this article is  to study the effect of overall spray angle and spray projected area for determination of spray propagation and investigate the effectiveness of this criterion.  The injector was a multi-hole direct injection injector and for producing of the required injection pressure the accumulator type fuel injection system was designed and built and employed in the experiments. According to empirical study, it was found that the spray overall angle characteristic is not an appropriate criterion for measuring the spray propagation. the spray projected area also was investigated and it was found that this characteristic is a correct criterion for measuring the spray propagation especially for the multi hole GDI injectors spray. The Schlieren method was used for spray imaging and the spray projected area of image was extracted using image  processing technique. The propagation of the spray was also investigated for different chamber and injection pressures, which resulted a decreasing and increasing procedure in propagation with increasing environmental and injection pressures respectively. Also, investigation of the spray for chamber pressures less than the atmosphere pressure comparing with higher than atmosphere pressures, showed that at pressures less than the atmospheric pressure, the speed of spray propagation increases with increase of injection pressure, while at pressures More than the atmosphere pressure, this speed is almost constant.