STAGNATION TEMPERATURE MEASUREMENT AT HIGH MACH NUMBER USING VERY SMALL PROBES

Abstract : A series of tests of simple thermocouple probes of different sizes was conducted in a Mach 6 flow at a stagnation pressure of 800 psi and stagnation temperature of 715 plus or minus 10F. The results support the argument introduced that as the physical scales are reduced, the temperature recovery factor tends to unity. In tests of the smallest probe (which uses 0.0005 in wires in a 0.032 in diameter insulator) at angles of attack up to 20 deg, stagnation pressures from 640 to 910 psi and stagnation temperatures from 685F to 920F, the recovery factor was within 1.5% of unity. The implication of these results is that the measurement of stagnation temperature in a high Mach number flow does not require a complex probe but rather, a small one. There is always a wire size for a given probe size which will measure stagnation temperature in a given flow to within 1%. (Author)