Pulsed Jet Ejector Characteristics

Abstract

An experimental study is carried out to investigate the flow field of a pulsed jet ejector thrust augmenter operating at a mean primary jet exit mach number of Mj Mj Mj = 0.30 and at a pulsing frequency of f = 210 Hz. Phase-locked Particle Image Velocimetry (PIV) is used to obtain the detailed spatio-temporal evolution of the ejector flow field. Experiments were carried out at three dierent area ratios that help to define the conditions for maximum thrust augmentation. In the presence of the ejector duct, the pulsed jet primary vortex induces a secondary vortex at the ejector wall. The induced vortex strength was found to be maximum, as defined by its circulation, at the condition of the maximum thrust augmentation. The presence of the counter rotating vortex pair results in enhanced mixing which in turn produces increased thrust augmentation. The measurements suggest that a compact ejector (L/D 3) with an area ratio (duct area/primary nozzle exit area) of about 10 can produce a thrust augmentation ratio (total thrust/primary nozzle thrust) of about 2.3.