Investigation on Incompressible Lobed Mixer–Ejector Performance

Abstract

A semi-empirical one-dimensional model is developed for the incompressible lobed mixer–ejector design and optimization analysis. This model is deduced on the conservation relations of mass, momentum, and energy by using the control volume method with consideration of the incomplete mixing in a short mixing duct and the pressure loss of the intake system. To capture two key empirical parameters for charactering the operating point of the lobed mixer–ejector in this analytical model, the nonuniformity of the momentum profile at the mixing duct exit and the inlet loss coefficient of secondary flow, a series of three-dimensional numerical computations are carried out. By experimental validation, the semi-empirical model established in the present work is reliable for predicting the lobed mixer–ejector performance. The results show that there is an optimum area ratio of mixing duct corresponding to the peak entrainment for a given mixing duct length. As the mixing duct length increases, the mixing process between primary flow and secondary flow is improved toward complete mixing, raising the critical value of mixing ductarea ratio corresponding to the peak flow ratio. When the secondary flow area at the mixing duct inlet is small, the intake opening area of the entrained flow has relatively weak influence on the momentum profile nonuniformity. When the secondary flow area at the mixing duct inlet is large, the intake opening area of the entrained flow has adverse influence on the mixer–ejector performance.