Experimental investigation of cavitation inside a plain orifice injector

Injector elements having narrow flow passages are more susceptible to cavitation. It is important to understand cavitation phenomena occurring inside the injector flow passage as it can lead to fluctuation in propellant flow rate in the combustion chamber. The focus of the present work is to investigate the cavitation phenomena occurring inside the nozzle, their interaction with the internal flow and the characteristics of the external flow. Different injector elements of varying length to diameter (L/D) ratios were designed and realized. Experiments were conducted at different flow regimes to capture the various modes of cavitation occurring inside the injector element. A high speed camera was used to investigate the internal and external flow behavior. As the length and diameter increases, the injection pressure required to initiate cavitation increases. The cavitation regime extends throughout the injector length as pressure varies. The optimum cavitation number observed was found to be optimum in the range of 1.5 to 2.0.