Experimental determination of geometric parameters for an annular injection type supersonic ejector

The effects of four geometric parameters of an annular injection supersonic ejector namely, the primary nozzle exit-to-throat area ratio, the contraction angle of the mixing chamber the cross-sectional area and L/D ratio of the second-throat on the performance parameters including the secondary flow pressure, the starting pressure and unstarting pressure were investigated experimentally. The starting pressure exhibits linearly proportional dependence on the throat area ratio when the mixing chamber length is less than a certain critical value. For a longer mixing chamber the starting pressure is proportional to the mixing chamber length while the unstarting pressure depends on the throat area ratio only. The geometric parameters of the second-throat do not affect the static pressure of the secondary flow. This implies that the secondary flow is aerodynamically choked in the mixing chamber and the static pressure of the secondary flow is determined by the choking condition since the mixing chamber of the annular injection ejector is relatively long. Based on the findings by the experiment, a simplified analytical model was proposed to predict the secondary flow pressure. The predicted secondary flow pressure agrees reasonably well with the measurement for a small contraction angle of the mixing chamber.