Numerical investigation on the flow structures of the multi-strut mixing enhancement ejector

Abstract

A new type of multiple jets ejector called the multi-strut mixing-enhancement ejector (MSE) has been developed in previous studies. The excellent suction and supercharging abilities of this ejector have been demonstrated through a series of cold flow tests. However, the current knowledge on MSE is limited. Numerical investigations on MSE have not been conducted in previous studies. Therefore, the present study aims to conduct a series of numerical investigation on the MSE to analyse the transform regularities of the flow structures at various secondary flow conditions and explore the evolution processes of multiple 2D jet interactions in a confined space. Results show that the flow structures of the MSE are extremely complicated and different from the traditional single jet supersonic ejector. When the secondary flow is zero, the collisions of multiple supersonic primary flows generate multiple abreast oblique shocks, and the intersections and reflections of these oblique shock waves form a shock diamond matrix in the mixer and convergent section. In addition, a novel head-shape pseudo shock is observed in the secondary throat due to the coupling interactions of multiple oblique and adverse pressure gradients, which contain three parallel X-type shocks and an extremely intricate ‘butterfly-type’ shock behind. Under various secondary flow mass rate conditions, the secondary flows limit the expansions of the primary flows in the supersonic diffuser, thereby decreasing the number and intensity of oblique shocks in the mixer and convergent section, followed by the changes in the head shape of the pseudo shock in the secondary throat. Besides, the evolution processes of multiple 2D jets interactions demonstrate a complicated 3D effect. The wave loss, friction loss and mixing loss are the main factors that affect the evolution processes of multiple jets in the mixer and convergent section. The waves cause the jets to expand and compress along the flow direction, the friction loss results in vertical separation at the interface between the primary jets and the walls, and the mixing of flows causes the horizontal recess of the primary jets. These factors also have different effects on the jet’s evolution under various secondary flow conditions. The shock and friction losses are the main factors that affect the jet’s evolution when ER is small (ER ≤ 0.037). However, with the increase in ER, the effect of both losses weakens, and mixing loss becomes the dominant factor.