Investigation of the Mach Number Effects on Fluid-to-Fluid Interaction in an Unsteady Ejector with a Radial-Flow Diffuser

The concept of fluid-to-fluid direct interaction whereby energy can be transferred among the interacting fluids was demonstrated and shown to be conceivable in non-steady ejectors. Unlike steady ejectors, the mechanism responsible for the energy transfer is reversible and thus higher efficiencies are expected. Of interest is to investigate the effects of Mach numbers on the performance of non-steady ejectors with radial-flow diffusers. The radial-flow ejectors usually lead to higher-pressure ratios with fewer stages. The Mach number of the primary fluid flow emerging out of the free-spinning rotor is considered an important factor among various parameters that affects the process of energy transfer. Specifically, the flow field is investigated at two Mach numbers 2.5 and 3.0 utilizing rectangular short-length supersonic nozzles for accelerating the primary fluid. Also the effects of increasing the total pressure of the primary fluid on the flow field are investigated. The results are compared with earlier investigation at Mach number 2.0, which showed significant enhancement in energy transfer with increase in Mach number. Fundamental to the enhancement of these devices performance relies on the management of the flow field in such a way to minimize entropy production. Numerical analysis utilizing a package of computational fluid dynamics was used for the investigation.