Controlling Separation on a Simulated Compressor Blade Using Vortex-Generator Jets

Abstract

Flow control using vortex-generator jets has been used to control a separating boundary layer on the surface of a flat plate in the presence of a pressure distribution equaling that on the suction surface of a compressor blade. A parametric study has been performed in which the skew angle and jet velocity of steady jets have been varied. In addition to steady blowing, the jets have been pulsed over a range of reduced frequency from 0.5 to 7.0. Steady blowing with a jet velocity greater than the inlet flow velocity was found to delay separation on the surface of the flat plate and reduce the loss coefflcient of an equivalent cascade blade by 36 %, relative to the unactuated case. This jet velocity is equivalent to an injected mass flow rate of 0.13 % of the inlet mass flow rate. With pulsed blowing, the same loss reduction was achieved over the unactuated case using 40% less mass flow. This loss reduction, however, required a reduced frequency greater than 6.0 and a peak jet velocity equal to 1.5 times the inlet flow velocity. This corresponds to a jet Mach number in a real compressor of 1.125, pulsing at more than 180 kHz.