Rapid Assessment on Flow Parameter Matching Scheme of a Combustion Wind Tunnel

Abstract

A rapid assessment approach based on oblique-shock-wave and isentropic relations is established to analyze multiple freestream parameter matching schemes in ground-based tests of airframe/propulsion integrated vehicles in a combustion wind tunnel. Shock and isentropic compression configurations are introduced to estimate the deviation range of aerodynamic properties to ture flight. It is found that the deviation of the oblique shock angle and the post-shock pressure coefficient between in vitiated and clean air is rather small while for an isentropic compression configuration the pressure coefficient deviation is comparatively big, when the incoming flow Mach number is matched. If the total pressure and dynamic pressure are simultaneously matched regardless of the restrictions on the matching of Mach number, however, a remarkable reduce emerges in the difference of wave structures as well as aerodynamic forces. Analysis shows that it is the decrease of incoming flow Mach number that make the P0Q-matched condition better than the M-matched condition. Considering the aero-propulsion integrated performance, h0P0Q matching scheme is an instructive choice. Numerical simulation further indicates that if appropriate flow parameter matching scheme is selected, combustion wind tunnels can even reproduce the aerodynamic characteristics closer to true flight than conventional ones.