This paper describes a numerical study of gas-gas ejector (jet pump) performance. The developed
model used to study performance determination for different operating conditions and geometrical
configurations of ejector. The performance of ejector obtained based on a simulation procedure of
linearized and axisymmetric subsonic and supersonic flow using Fluent Package. The CFD model
used to evaluate the performance of three different ejector geometries that tested under different
working conditions. A conventional finite-volume scheme utilized to solve two-dimensional
transport equations with the standard k-ω SST turbulence model. The model is solved in three
regions namely, the primary flow nozzle, the secondary flow channel, and the region of interaction
between the supersonic nozzle jet and the secondary flow. The effect of the mixing part and tail
section (pipe or diffuser) geometries on the ejector performance studied. In addition, the effects of
gas motive pressure on the static pressure distributions are also studied. The computational results
are validated using published experimental data, where acceptable agreements exist. The
numerical results indicate that the ejector geometry has a pronounced effect on the flow
parameters (i.e., pressure and gas velocity) and the ejector performance. In addition, predicted
numerical results indicate that when the motive-stream velocity exceeds the speed of sound, shock
waves are unavoidable inside ejectors and that shock wave pattern in mixing part has a dominant
effect on ejector performance. In addition, the results indicate that the shock location inside the
nozzle and the separation point are affected by the motive pressure. The results show also that
configuration with convergent-divergent mixing section is much better for mixing process than the
other tested configurations.