Optimization study of a two-stage ejector–diffuser system. (October 2016)

• Record Type: Journal Article
• Authors: Kong, Fanshi; Kim, H.D.
• Is Part Of: International journal of heat and mass transfer. Volume 101(2016:Oct.)
• Page Start: 1151
• Page End: 1162
• Publication Date: 2016-10
• Subjects: Compressible flow -- Entrainment -- Power coefficient -- Two-stage ejector–diffuser system -- Shock wave -- Supersonic flow; Heat -- Transmission -- Periodicals; Mass transfer -- Periodicals; Chaleur -- Transmission -- Périodiques; Transfert de masse -- Périodiques; Electronic journals; 621.4022
• DOI: 10.1016/j.ijheatmasstransfer.2016.05.129
• Languages: English
• ISSNs: 0017-9310

Abstract

Highlights: Two-stage ejector–diffuser system is numerically designed and optimized. Inherent relations among vortex, choking state and system performance are found. Geometrical parameters associated with the system performance were assessed. A new coefficient COPR is proposed to specify two-stage ejector benefits. The best model has 442.8% performance improvement over the conventional one. Abstract: Two-stage ejector–diffuser system has been suggested to be a useful alternative configuration for utilizing the redundant momentum of the discharged flow. As compared with the conventional single-stage ejector–diffuser system, the performance can be significantly improved. However, there has been little investigation on the system optimization. This is one of the important reasons of limiting the engineering use of the two-stage ejector–diffuser system. In the present study, the major characteristics of a supersonic two-stage ejector–diffuser system have been investigated in detail using numerical methods. A fully implicit finite volume scheme was applied to the governing equations, with a RSM turbulence model. After very careful validation study with existing experimental results, many important geometrical parameters associated with the system performance were assessed. This provides an insight to achieving optimal performance in terms of mass flux of entrained flow, pressure recovery, total pressure loss and power coefficient. The results obtained showed that the two-stage ejector–diffuser system produces an improved performance of about 4 times over the single ejector system.