Effect of Entraining Diffuser on the Performance of Bent Exhaust Ejectors

Abstract

This paper presents experimental data from subsonic air-air bent ejectors with ring type entraining diffusers. Three oblong ejectors with different degrees of bend in the mixing tubes were used in the study. The experiments were performed on a wind tunnel capable of providing air up to 2 kg/s. The performance was studied at different primary flow temperature and swirl conditions. Pressure, velocity and temperature was measured upstream of the primary nozzle and at the exit of the diffuser. Detailed traverses were done with 7-hole probes and thermocouples. As would be expected, the performance of the ejector decreases with the degree of bend. The diffusers were added to improve the pressure recovery in the ejector and for self cooling of the diffuser. Improved pressure recovery typically leads to improved pumping in ejectors. With the diffuser added, the overall length of the ejectors was increased from 2.5 to 3.8 times the mixing tube equivalent diameter. Different trends of pumping ratio with the swirl conditions were obtained with hot and cold primary flows.