Supersonic Inlet Simulator - A Tool for Simulation of Realistic Engine Entry Flow Conditions

Serious difficulties have been experienced in the development of some supersonic aircraft due to engine stability problems arising from previously unknown characteristics of the flow field at the engine-inlet interface plane. To ensure against further unknowns, an F-15 inlet simulator was designed, constructed, and installed in an altitude test cell for realistic engine testing with inlet flow distortions. The simulator has the aerodynamic shape of the F-15 inlet from the second ramp to the engine inlet plane. Interface flow conditions are produced by accelerating air through a two-dimensional nozzle to duplicate the last oblique shock wave of the aircraft inlet. The terminal shock, spillage past the cowl lip, and inlet bleeds are reproduced. Forebody effects, angle of attack, and sideslip can be simulated. Scale model tests used to develop the simulator concept are reviewed. Experimental results from the full-scale inlet simulator are presented showing the ability to reproduce time-variant inlet flow fields, including the most severe inlet patterns, buzz, and hammershock. Engines can be tested with the combined destabilizing effects of power lever transients, Reynolds number, time-variant distortions, and planar pulsations.