PROBING TECHNIQUES FOR USE IN HIGH TEMPERATURE REACTING FLOWS

Abstract : A basic probe has been designed which consists of a 1/8-in.-diam, water-cooled copper probe with an inside diameter of 0.050 in. These probes may be aspirated to take a gas sample and temperature reading, or used without aspiration to measure total pressure. Two systems currently being investigated to measure temperature are quartz-coated thermocouples and pneumatic thermometers. These probe designs were chosen because they should not include the heat of recombination of non-equilibrium gases in the temperature reading as would a calorimeter-type total enthalpy probe. The gases are analyzed on line with a bistable fluid oscillator having an oscillation frequency that is a function of the molecular weight of the sample. No quantitative theory of fluid oscillators is available; however, observations are given of the effect of some of the design parameters on performance. A study was made of the effect of probe shape and Mach number on the validity of samples taken in a supersonic stream. For hydrogen-nitrogen mixtures at a static pressure of 1 atm, no change between the free stream and the sample was seen in any of the tests.