Experimental Study of the Effect the Basic Geometrical Parameter and the Active Gas Nozzle Expansion Ratio Have on the Performance Characteristics of Supersonic Gas Ejectors Fitted with a Conical Mixing Chamber

The article presents the results from experimental investigations of supersonic gas ejectors equipped with a conical mixing chamber having different lengths carried out for a number of values of the basic geometrical parameter and the active gas nozzle expansion ratio. Certain results obtained from a thermodynamic analysis of the ejectors have been confirmed in a wide range of geometrical parameters, specifically, that there is a possibility to obtain—at the same ejection factor—the first and second critical modes, which differ from each other in the motion pattern of mixing flows and in the efficiency of mixing processes occurring at different passive gas pressures; that there exist three zones in the throttle performance, which correspond to two critical modes and one subcritical mode (it is worthy of noting that the transition from the first critical mode to the subcritical mode that occurs during a growth of back pressure is accompanied by a step-like increase of passive gas pressure, whereas the transition from the subcritical mode to the second critical mode and vice versa occurs without a break in the continuity of changing the ejector’s throttle performance parameters); and that there may be two varieties of the second critical mode: with supersonic and sonic gas mixture flow velocities in the conical chamber outlet section. It is shown that the basic geometrical parameter and the active gas nozzle expansion ratio strongly influence the ejector’s operating and throttling performance characteristics, as well as the mixing chamber optimal length. Experimental dependences of the supersonic gas ejector’s adiabatic efficiency on the conical mixing chamber length are obtained at different values of the basic geometrical parameter and the active gas nozzle expansion factor for the first and second critical modes. It is shown that the optimal mixing chamber length depends on the ejector operating mode. Recommendations for selecting the optimal length of the supersonic gas ejector’s conical mixing chamber within the studied range of parameters for the first and second critical modes are given.