Experimental and Numerical Analysis on the Internal Flow of Supersonic Ejector Under Different Working Modes

ABSTRACT

Supersonic ejectors involve very complex phenomena such as interaction between supersonic and subsonic flows, shock trains, instabilities, which strongly influences the performance of supersonic ejector. In this study, the static pressure distribution along the ejector wall and Mach number distribution along the axis are used to investigate the internal flow field of supersonic ejector. Results indicate that when the back pressure is much less than the critical back pressure, there are two series of shock trains, and the change of the back pressure will not affect the flow field before the effective area section, so the entrainment ratio would remain constant. The second shock train moves further upstream and is combined with the first shock train to form a single shock train as the back pressure rises. When the back pressure is greater than the critical back pressure, the position of the shock train, the static pressure at its upstream and the entrainment ratio, will be affected. The “effective area section” in the mixing tube is obtained. The effective area section position moves downstream with the increase of the primary flow pressure, while it moves upstream with the increase of the secondary flow pressure. The entrainment ratio shows inversely proportional relationship with the effective section position. Besides, the first shock train length increases with the increase of primary flow pressure or secondary flow pressure. The critical back pressure represents direct proportional relationship to the first shock train length.

Nomenclature

k	=	turbulent kinetic energy, m2·s−2
Ma	=	Mach number
P	=	pressure, MPa
Xa	=	axial distance, mm

Greek symbols

ϵ	=	turbulent dissipation rate, m2·s−3
ω	=	entrainment ratio

Subscripts

B	=	back pressure
H	=	high-pressure/ primary flow
L	=	low-pressure/secondary flow

Acknowledgements

This work was supported National Natural Science Foundation of China (No. 51476128 and No.51436006).

Additional information

Notes on contributors

Weixiong Chen

Weixiong Chen is an associate professor of State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an, China. He received his Ph.D. from Xi'an Jiaotong University in 2013. His area of interest is the mixing mechanism inside the ejector, two-phase flow (water and natural gas) inside the supersonic ejector, steam/gas-water two-phase flow, emulation, and optimization of thermal system.

Kangkang Xue

Kangkang Xue is a master student of State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University. His present work is to investigate the performance of gas-liquid ejectors based on computational fluid dynamics simulation. He is interested in the application of supersonic ejector.

Huiqiang Chen

Huiqiang Chen received his masters degree from Xi'an Jiaotong University in 2016. His present work is to investigate the performance of gas-liquid ejectors based on computational fluid dynamics simulation. He is interested in the application of supersonic ejector.

Daotong Chong

Daotong Chong is an associate professor of State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an, China. He received his Ph.D. from Xi'an Jiaotong University in 2008. His research interests include supersonic ejector, steam/gas-water two-phase flow, mixed convection in tubes, emulation, and optimization of thermal system.

Junjie Yan

Junjie Yan is a professor of State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University. He received his Ph.D. from Xi'an Jiaotong University in 1998. He is the committeeman of multiphase flow committee of Chinese society of engineering thermophysics. His research interests include enhanced heat transfer, emulation and optimization of thermal system, steam-water two-phase flow, phase change heat transfer, cogeneration of cooling, heating and power, process control.