Experimental pressure and heat transfer investigation over a 'directed-energy air spike' inlet at flow mach numbers of 10 to 20, stagnation temperature of 1000 K, and arc powers up to 127 KW.

摘要

The objectives of the experimental Directed-Energy Air Spike (DEAS) investigation were to measure the pressure and heat transfer over the Lightcraft forebody surface, and to capture Schlieren photographs of the shear layer/shock wave structure required to understand the hypersonic flow, and to assist in the design of the DEAS for very advanced, beam-boosted vehicles easily capable of reaching orbital velocity.; A 6-in. diameter aluminum model was fabricated and fitted with pressure transducers and thin-film platinum heat gauges. A 6-in. long slender plasma torch was placed at the stagnation point, and an electric arc was triggered at the tip of the plasma torch to simulate the concentrated beamed energy ahead of the moving vehicle. Freestream Mach numbers of 10 to 20 and stagnation temperature of 1000 K were selected to conduct the pressure and heat transfer measurements over the DEAS model in the Hypersonic Shock Tunnel (HST).; When the bare DEAS model was tested in the HST pressure ratio and heat transfer measurements as well as Schlieren photographs were found to be qualitatively similar to the available experimental and theoretical results. The spiked blunt body with and without cooling gas were very similar to each other. The measured pressure data indicate that the aerodynamic drag of the spiked blunt body is lower than the aerodynamic drag for the blunt body without a spike.; For the "power-on" configuration the pressure ratios are at the same order of magnitude as the corresponding results for the spiked blunt body with and without cooling gas. As a consequence, the concentrated energy ahead of the DEAS model reduces the Mach number impacting the forebody surface and therefore, the aerodynamic drag.; The heat transfer measured on a full DEAS powered configuration is much higher than that of the power-off configurations. The non-uniformity of the heat transfer measured across the DEAS model surface is probably due to: (a) the arc heat source that generates nonlinear wave; (b) the small pieces of the solid particles that travel along with the flow; and, (c) the effect of the arc power that deflects the shock wave away from the vehicle.