Computational Analysis of Mixing Guide Vane Effects on Performance of the Supersonic Ejector-Diffuser System

Abstract

The flow field in the ejector-diffuser system and its optimal operation condition are hardly complicated due to the complicated turbulent mixing, compressibility effects and even flow unsteadiness which are generated inside the ejectordiffuser system. This paper aims at the improvement in ejector-diffuser system by focusing attention on entrainment ratio and pressure recovery. Several mixing guide vanes were installed at the inlet of the secondary stream for the purpose of the performance improvement of the ejector system. A Computational Fluid Dynamics (CFD) method based on Fluent has been applied to simulate the supersonic flows and shock waves inside the ejector. A finite volume scheme and density-based solver with coupled scheme were applied in the computational process. Standard k-ω turbulent model, implicit formulations were used considering the accuracy and stability. Previous experimental results showed that more flow vortexes were generated and more vertical flow was introduced into the stream under a mixing guide vane influence. Besides these effects on the secondary stream, the mixing guide vane effects on the shock system of the primary stream were also investigated in this paper. Optimal analysis results of the mixing guide vane effects were also carried out in detail in terms of the positions, lengths and numbers to achieve the best operation condition. The comparison of ejector performance with and without the mixing guide vane was obtained. The ejector-diffuser system performance is discussed in terms of the entrainment ratio, pressure recovery as well as total pressure loss.

A Validated Numerical-Experimental Design Methodology for a Movable Supersonic Ejector Compressor for Waste-Heat Recovery

“…Ejector performance is strongly dependent on the mixing phenomena inside the mixing chamber. As investigated by Kong et al [23], both flows should be fully mixed in the mixing chamber to reduce the energy loss in the diffuser section. A good mixing chamber design enhances the tangential-shear interaction between primary and secondary flows with lower loss in the mean kinetic energy of the flow.…”

Analytical and computational studies on the performance of a two-stage ejector–diffuser system

“…However, its efficiency is relatively low compared with other fluid machinery. For the past decades, many researches have been made to reduce the energy loss and increase the mixing efficiency by optimizing the ejector geometries in terms of supersonic nozzle [7,8], mixing chamber [9] or additional mixing guide vanes [10]. While those optimization works are still not satisfactory due to the existing of complicated flow structures inside an ejector in aspects of mixing flow, shear layers, vortexes, shock waves and so on [11][12][13][14].…”