Mixer-Ejector Noise-Suppressor Model

Abstract

A flexible and efficient compressible mixer-ejector model is described. This model is used to predict the performance of ejectors employing lobed mixers. Through comparisons with experimental data, the model is shown to qualitatively capture the impact of streamwise vorticity on the evolution of the mixing layer and to quantitatively predict the change in the pressure coefficient through the duct associated with the mixing process to within 15 %. The relative accuracy, speed, and flexibility of the model make it useful as a preliminary design tool. Two design trade studies are performed with the model. First, the model is used to assess the impact of streamwise vorticity on the thrust and pumping performance of a supersonicsubsonic mixer-ejector; for the mixer geometry utilized in this study, pumping and thrust augmentations are associated with the addition of streamwise vorticity. Second, the impact of mixer height on the effectiveness of streamwise vorticity is evaluated. The results of this study demonstrate that the effectiveness of streamwise vorticity decreases with increasing lobe height-to-wavelength ratio, and for the higher height-to-wavelength ratios investigated, a net performance penalty is associated with the addition of streamwise vorticity.