Effect of Primary Nozzle Geometry on the Performance of Rectangular Ejectors

An experimental study of the effect of primary nozzle geometry on the performance characteristics of a rectangular subsonic ejector was conducted. Four primary nozzle configurations having rectangular and notched-rectangular exit geometries each with and without boundary layer swirl vanes were studied in these experiments. The ejector and all primary nozzles had equal aspect ratios (defined as the ratio of the large to small dimensions) of 2.8. The primary jet Mach number and Reynolds number were kept constant at M=0.06 and for all cases. After installation of each nozzle in the ejector throat, the mean and fluctuating velocity field at the ejector exit plane and three other downstream stations were mapped using a single hot wire probe. Mass flow ratio, spreading rate, and ejector pumping were calculated from the above measurements. The flow measurements indicated that the ejector's mass flow rate, spread rate, as well as pumping characteristics were enhanced by installation of boundary layer swirl vanes to the exit of the primary nozzles.