Experimental study on the entrainment performance and flow choking phenomenon of a two-stage multi-nozzle ejector

A two-stage multi-nozzle ejector experimental system is established, and the pressure distribution on the wall and in the flow field of the test model is measured when the total pressure of the two-stage primary flow changes. Results show that when the total pressure of primary flow increases, vacuum chamber static pressure decreases to its lowest limit of 1 kPa, and then begins to rise. Flow choking mechanism of two stage ejector is clarified. If the total pressure of the first stage primary flow is low, the flow in the second stage ejector first reaches the choking state when the total pressure of the second stage primary flow increases, which causes the rise of first stage back pressure, and then the first stage ejector reaches the choking state. If the total pressure of the first stage primary flow is high, the increase of total pressure of the second stage primary flow reduces the back pressure of the first stage ejector and therefore the first stage ejector first reaches the choking state, and then the second stage reaches the choking state.