Characteristics analysis of shock wave near nozzle in ejector

Abstract

With increasing concern of environmental and energy issues, ejector is more and more widely applied in various fields owing to the advantages of using low grade heat. In the ejector, the Mach waves may be generated at the nozzle outlet and diffuser chamber. Under different expansion ratios, the Mach waves at the nozzle outlet will appear to be expansion waves, oblique shock waves and normal shock waves successively. This paper theoretically studies the characteristics of the Mach waves at the nozzle exit of the ejector with steam, ammonia, R22, R290, R134a and R600a as working fluids. The results indicate that the higher the adiabatic indexes, the lower the Mach wave intensity if there are oblique shock waves or expansion waves in the nozzle exit and; the cross section ratio and shock wave intensity vary gently with the rise of expansion ratio. At the same time, expansion wave intensity and shock wave intensity also decrease with the increase of nozzle cone angle. Therefore, there should be an optimal parametric range for nozzle structure design to obtain higher efficiency.