Investigation of Supersonic Air Ejectors : Part 1. Performance in the Case of Zero-Secondary Flow

The performance of a supersonic air ejector in the case of zero-secondary flow was studied by varying the Mach number of the primary nozzle and the throat area ratio of the mixing tube to the primary nozzle. As the result, it has been shown that an optimum throat area ratio exists for each Mach number of the primary nozzle in which case the vacuum performance of the ejector becomes maximum with a minimum stagnation pressure of the primary flow. The physical meanings of the optimum throat area ratio and other ejector characteristics have been clarified from the results of pressure measurements and optical observations. Furthermore, modifying a previous method in the case of a constant-area mixing tube, the ejector performance was calculated for a variable-area mixing tube in the case of a larger throat area ratio than the optimum one. Calculated values agree well with the experimental results.