Theoretical and Experimental Pressure Recovery of Sweptback Normal Shock Inlets

Abstract

A theoretical analysis of the performance of normal shock inlets having sweptback faces is presented. The analysis, which is based on a continuity and stream-thrust balance without regard to the internal shock patterns, permits the prediction of the critical total pressure recovery of a sweptback normal shock inlet as a function of face angle, angle of attack, and free-stream Mach Number. The theory shows that the performance of a normal shock inlet at positive angles of attack can be significantly improved without penalizing the performance at zero angle of attack by sweeping back the inlet face. The theory also shows tha t the supercritical mass-flow ratio for the normal shock inlets is independent of Mach Number and depends only upon the geometry of the inlet and the angle of attack. A series of normal shock inlets having face angles of 0°, 10°, 20°, 30°, and 40° was tested at Mach Numbers of 1.62 and 1.99. The experimental results are shown to be in good agreement with the theory. A D f F g m m M Ps Pt R Tt V W a 0 7 P 0 ibsc 0 = 1 = 2 = 3 = NOMENCLATURE = area = diameter = stream thrust per unit area = stream thrust = acceleration due to gravity = mass flow = Mach Number parameter defined in Eq. (3) = Mach Number = static pressure = total pressure = gas constant = total temperature = velocity = airflow = angle of attack = inlet face, angle = ratio of specific heats = density = parameter defined in Eq. (14) and tabulated in reference 1 ripts = free stream = inlet station = exit station at end of constant-area passage = end of subsonic diffuser