An Experimental Investigation of Hypersonic Stagnation Temperature Problems

Abstract

An experimental investigation of single-shielded hypersonic stagnation temperature probes was conducted in the GALCIT Leg No. 1 hypersonic wind tunnel and in the Jet Propulsion Laboratory 12-inch supersonic wind tunnel. By the combined use of both shield and base heating, a probe recovery factor of r = 1.0 was obtained over a range of Reynolds numbers at M_∞ = 5.75. By using the experimental data and simple heat balance equations, the probe losses, for the conditions investigated, were found to be in the proportion: shield conduction loss - 15 base conduction loss - 3 thermocouple conduction loss - 1 thermocouple radiation loss - 3/100 The typical decrease in probe recovery factor observed for decreasing Reynolds number appears to be related to a decrease in the base temperature and not to the wire conduction loss as commonly assumed. An optimum probe vent to entrance area ratio of A_v/A_e ≈ 1/2 was found and is shown to be a function of the number of vent holes used in the shield. No single calibration parameter was found that could relate the experimental recovery factors under all conditions.