Experimental Study of Oblong Exhaust Ejectors With Multiring Oblong Entraining Diffusers

This paper presents experimental data for the performance of two oblong, straight, air-air ejectors with four-ring oblong entraining diffusers. The effects of inlet swirl angle, nozzle diameter, and flow temperature on the ejector pumping, backpressure, wall pressure distribution, diffuser pressure recovery, and surface film cooling effectiveness were studied. The experiments were carried out on a hot gas wind tunnel that could provide primary mass flow rates up to $2.2kg∕s$ at ambient temperature and $1.8kg∕s$ at $500°C$⁠. Velocity, pressure, and temperature were measured in the annulus upstream of the primary nozzle, on the mixing tube and diffuser walls, at the diffuser gap inlets, and at the diffuser exit. A comparison between the performance of the oblong ejector and a round ejector indicated that for a short length ejector, the oblong ejector provided better overall performance in terms of pumping and velocity and temperature distributions.