Unsteady Ejector Performance: An Experimental Investigation Using a Resonance Tube Driver

A statistically designed experiment to characterizethrust augmentation for unsteady ejectors has beenconducted at the NASA Glenn Research Center. Thevariable parameters included ejector diameter, length,and nose radius. The pulsed jet driving the ejectors wasproduced by a shrouded resonance (or Hartmann-Sprenger) tube. In contrast to steady ejectors, anoptimum ejector diameter was found, which coincidedwith the diameter of the vortex ring created at thepulsed jet exit. Measurements of ejector exit velocityusing a hot-wire permitted evaluation of the massaugmentation ratio, which was found to correlate tothrust augmentation following a formula derived forsteady ejectors.IntroductionCurrently, efforts are underway to explore the use ofpulsed detonation engines (PDE) for aerospacepropulsion. Technical issues involved includeintegration, noise, and thrust to weight ratio. Adding anejector to a PDE may enhance thrust, and reduce noise.The ejector will then be driven by a pulsating flow. Paststudies of unsteady ejectors