Combined tangential-normal injection into a supersonic flow

Abstract

A combination of tangential and normal air injection into a Mach 3 airflow was experimentally studied. A rearward facing slot producing tangential injection at a nominal Mach number 1.7 was operated at several different total pressures. An array of transverse tubes of height equal to the slot height and placed just downstream of the slot was operated at two dynamic pressure ratios at both Mach 1 and 2.2. Mean flow measurements of static and total pressures were taken up to 20 slot heights downstream from which Mach number, density and velocity profiles, and entrainment rates were calculated. Various dimensions and spreading angles of the mixing regions were measured directly from nanoshadowgraphs and spark schlieren photographs. Large eddy structures were produced in several cases, leading to increased entrainment of the freestream. For some cases, heated air was injected through the normal tubes, and the jet total temperature decay was measured downstream. It can be seen from the data that the mixing rate can be significantly increased by the combined tangential-normal injection design over tangential slot injection alone, with up to 92% more entrained mass.