Hypersonic inlet performance from direct force measurements

Abstract

The problem of establishing one-dimensional values of supersonic combustion inlet performance is approached from the standpoint of direct internal drag measurements. Analytically, one-dimensional inlet component efficiencies can be obtained with mass, momentum, and energy considerations as a function of inlet internal drag. Such efficiency values reflect combined shock wave and viscous losses. Direct measurements of model internal drag were made in a hypersonic shock tunnel to determine the experimental feasibility of this concept for an axisymmetric inlet designed for unity mass flow ratio. With this model, effective internal drag isolation was accomplished by physical separation of the model internal surfaces from adjacent parts of the inlet. With such a technique, a correction must be made to the measured internal drag to account for balance cavity forces. The results of this experiment indicate that, through careful model design, the magnitude of such corrections can be minimized and applied to the measured internal force in an accurate and consistent manner.