The Characteristics of Swirl Coaxial Injector Under Varying Geometric and Environmental Conditions

Abstract

It is known that the recess can augment mixing efficiency and flame stabilization through the internal mixing of propellants. So, various experiments, such as stroboscopic photography, PDPA and mechanical patternator, were performed at 8 cases of recess length to grasp its effect on the spray characteristics. In the emulsion injection region, spray angle and breakup length increase with increase of recess length, and which can be explained by the formation and decay of wave inside the recess region. As the recess length increases, the mean drop size increases due to the increase of effective film thickness and the decrease of spray angle. And the mixing efficiency increases with recess length, but in the case of very deep recess length, the mixing efficiency decreases. Also, spray characteristics in high-pressure environment were studied, and notable change of spray patterns are observed. Aerodynamic force of ambient gas significantly affects the breakup of a swirl spray, however, the breakup mechanism of liquid-liquid swirl coaxial spray is much controlled by the impact force by the interaction of propellants. Lastly, our experimental results according to the ambient gas pressure and injection velocity were compared with the linear instability theory. As a result, because attenuation of sheet thickness could affect the sheet breakup mechnism, it must be considered in the linear instability theory.