ARTICLE:

• CFD CHARACTERIZATION OF GEOMETRIC PARAMETERS IMPACT ON EJECTOR PERFORMANCE  download article

T. Marynowski
Université de Sherbrooke, Canada

P. Desevaux
Université de Franche-comté, France

Y. Mercadier
Université de Sherbrooke, Canada

ABSTRACT

The aim of the present work is to propose a parametric study to examine the impact of several geometric parameters on ejector performance. Calculations are performed using a 2D axisymmetric CFD model. The performance criteria retained for this study are the ejector capacity to suck and entrain an induced flow (entrainment performance) and to create vacuum. Validation is achieved on selected test cases by the comparison between computational results and experimental measurements. Tested parameters are secondary nozzle to primary nozzle throat-area, cylindrical mixing tube length and primary nozzle penetration length. Numerical simulations are performed for various ejector operating conditions (primary stagnation pressure, operation with and without induced flow). Results obtained confirm the existence of optimum performance of ejectors related to the nature of the flow regime and give insights on the optimal design of supersonic ejectors.
The ejector throat-area ratio is proved to strongly condition the transition conditions between the flow regimes in the ejector. This geometric parameter also affects the capacity of the ejector to suck and entrain secondary flow and the entrainment performance is improved for the highest throat-area ratio considered in this study. Concerning the impact of the mixing tube length, this investigation shows that small tube lengths cause a deterioration of the vacuum performance but an improvement of the entrainment capacity of the ejector. The primary nozzle position slightly affects the global performance of the ejector, especially in the mixed flow regime (without choking of the secondary nozzle) and conditions the optimum vacuum pressure that can be supplied by the ejector. It appears from this investigation that the best performance is achieved at small distances between the primary nozzle exit and the mixing tube inlet.

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