The air ejector has almost limitless application possibilities in engineering practice due that is to its simplicity. To determine the feasibility of using an ejector as a suction pump for boundary-layer air removal in the Two-Dimensional Supersonic Cascade Tunnel, especially when a portion of the tunnel′s air supply is used for its primary flow, both subsonic and supersonic air ejector tests were conducted. The tested eje relationship between secondary pressre (secondary vacuum chamber pressure) and primary stagnation pressure (primary pressure characteristics) during a zero-secondary-flow condition. (2) The effect of throat area ratio of primary nozzle to mixing tube on primary pressure characteristics. (3) The relationship between the minimum secondary pressure and throat area ratio. (4) The optimal operating conditions for a zero-secondary-flow subsonic ejector. (5) The effect of primary Mach numbers on a zero-secondary-flow supersonic ejector performance.