Method for Predicting the Aerodynamic Performance of Centerbody-Plug IR Suppressors.

摘要

An important consideration in the design of military aircraft engine exhaust diffusers is the need to reduce infrared radiation emanating from the engine, coupled with the need to maximize shaft horsepower. To aid the engineer in the solution of this problem, advanced mathematical techniques developed in this report have been applied to the solution of turbulent compressible swirling flow through curved-wall annular diffusers. This analysis has developed a generalized method for calculating an orthogonal coordinate system for arbitrary curved-wall annular ducts with cooling slots which is based on the Schwartz-Christoffel transformation. In addition, this analysis has developed a stable implicit numerical integration scheme for solving a nonlinear parabolic partial differential equation which does not require an iterative procedure to maintain second-order accuracy. Finally, it is noted that the procedure does not require an iterative procedure coupling the inviscid and viscous portion of the flow field but treats the entire flow field as a whole. A computer program has been developed using this analysis and applied to sample cases to demonstrate the capability of the analysis. Cases with and without slot-cooled walls have been calculated and compared with experimental data taken from the ST9 demonstrator IR suppression diffuser operating at different slot cooling flow rates for one engine operating condition.