An Analytical Study of the Scramjet Exhaust Expansion System. Part II.

Abstract : Design studies for a supersonic ramjet (Scramjet) to operate at high Mach numbers reveal that the practicality of the Scramjet concept is highly sensitive to the efficiency of the engine, particularly the nozzle. The operating range is such that the drag forces on the vehicle very nearly balance the total thrust that one would expect to obtain, so that small increases in efficiency of the nozzle result in large increases in the net thrust (thrust minus drag). This Air Force sponsored program is designed to study the losses in a scramjet type nozzle and develop methods of designing the exhaust expansion system to maximize the thrust or minimize the sum of the losses. The overall program includes a literature survey, the development of a computer program to design optimized axisymmetric and plug nozzles accounting for boundary layer drag losses, the development of a computer program to calculate the flow field in an axisymmetric nozzle with non-equilibrium chemical reactions, the development of a computer program to analyze the flow in a three-dimensional nozzle, and the development of a computer program to design optimized three-dimensional nozzles. The results of the first year's effort are summarized. The literature for computation of three-dimensional supersonic flow fields is reviewed. Computational schemes are presented using a three-dimensional method of characteristics approach and a finite difference approach. A pilot computer program for the finite difference scheme has been run and the results discussed. (Author)