Transpiration cooling for a vehicle with low radius leading edge

Abstract

A transpiration cooling system for avoiding overheating of an airfoil is provided. The airfoil is provided with a plurality of apertures and a source of pressurized fluid for providing a flow of fluid through the apertures to establish an aerodynamic radius. The aerodynamic radius of curvature of leading edge is sufficiently greater than the mechanical radius of curvature of the leading edge that peak heat flux is independent of the mechanical radius of curvature. The mechanical radius of curvature is preferably less than 50% of the aerodynamic radius of curvature during hypersonic operation. Preferably the mechanical radius of curvature is the smallest allowed by the fabrication method (i.e., a knife edge), such as being less than about 0.02 inches, preferably less than about 0.01 inches. The transpiration blowing rate can be adjusted so that the blowing rate and aerodynamic radius of curvature are relatively low except during periods of maximum heat flux, such as the shock-on-lip point. Since the mechanical radius of curvature is effectively zero, control of the aerodynamic radius of curvature provides complete control of peak heat flux. By adjusting blowing rate to the minimum necessary at any given velocity, transpiration consumption, drag and fuel injection are reduced or eliminated.