Reply To: Test Rigs for Exhaust Systems

[John Hind]

Hi Chris – CFD has been used for pulsing flows – see this paper from 2009.

Numerical simulation of transient flows
in a vacuum ejector-diffuser system
V Lijo1,HDKim1∗,G Rajesh2, and T Setoguchi3
1School ofMechanical Engineering, Andong National University, Andong, Republic of Korea
2Indian Institute of Space Science and Technology, Kerala, India
3Saga University, Saga, Japan

Abstract: The objective of the present study is to analyse the transient flow through the vacuum
ejector system with the help of a computational fluid dynamics method. An attempt is made
to investigate the interesting and conflicting phenomenon of the continuous entrainment into
the primary stream with limited mass supply from the secondary chamber. The results obtained
show that the one and only condition in which a continuous mass entrainment can be possible
in such types of ejectors is the generation of a recirculation zone near the primary nozzle exit. The
flow in the secondary chamber attains a state of dynamic equilibrium of pressure at the onset of
the recirculation zone. A steady flow assumption in such ejector systems is valid only after the
dynamic equilibrium state.
Keywords: compressible flow, ejector, internal

Proc. IMechE Vol. 224 Part G: J. Aerospace Engineering