18 May 2017
In this research, experimental and numerical investigations have been conducted on the driving flow Mach wave inside ejectors under off-design operation conditions. Numerical investigation has been conducted by the method of characteristics, and a simulation model was established to obtain the driving flow development from the nozzle exit. The influence of Mach waves from the nozzle exit was taken into consideration in the simulation model. Visualization experiment has also been conducted to validate the simulation results in the current research. Through this investigation, the influence of Mach wave on the driving flow boundary development is discussed. The expansion wave from the nozzle exit increases the driving flow regime in the under-expanded condition, which has negative impact on ejector performance. The results show that the Mach wave should be considered when the ejector is operated under off-design working conditions, and appropriate nozzle structure design was able to restrain the effect of the expansion wave, which improves ejector performance.