Aerothermodynamic Performance Enhancement of Sphere-Cones Using the Artificially Blunted Leading-Edge Concept

Artificially blunted leading edges created by the use of a flow-through channel sized to choke at supersonic conditions have been shown to be effective in significantly reducing drag in high-speed flow over blunted airfoils. Results of work to apply the concept to blunted sphere-cones and the use of a channel at a leading edge to enhance lift are presented. This enhancement is caused by the internal flow creating suction at the channel lip. Proof-of-concept numerical simulations on various sphere-cone configurations at different flight conditions show the concept's effectiveness in reducing drag of axisymmetric bodies. Experimental data are used to validate the predicted drag reduction at alpha = 0 deg, Mach 2.25-2.5 range, and sea-level conditions. Direct correlations between the channel size and drag reduction, lip geometry and lift increment, as well as between the channel lip radius and peak heat-transfer rates, were established and characterized using an efficient concept evaluation method. These polynomial models for force coefficients and heat-transfer rates are used by a gradient-based optimizer to generate derivatives of a 10-deg sphere-cone with the concept for operation at Mach 7, 20-km altitude. These geometries had approximately 5 percent higher lift-to-drag ratio and similar peak heating rates as the baseline. To mitigate the potential system-level drawbacks caused by a straight channel, a cowl-like derivative with curved channels exhausting from the forebody was investigated and found to provide comparable performance enhancement. (Author)