Concentration probe measurements in a Mach 4 nonreacting hydrogen jet

Abstract

A new probe technique is introduced for the measurement of concentration in binary gas flows. The new technique is demonstrated through application of the probe in a Mach 4 nonreacting jet of hydrogen injected into a nominally quiescent air environment. Previous concentration probe devices have mostly used hot wires or hot films within an aspirating probe tip. However, the new technique relies on Pitot pressure and stagnation point transient thin film heat flux probe measurements. The transient thin film heat flux probes are operated at a number of different temperatures and thereby provide stagnation temperature and heat transfer coefficient measurements with an uncertainty of around ±5K and ±4% respectively. When the heat transfer coefficient measurements are combined with the Pitot pressure measurements, it is demonstrated that the concentration of hydrogen within the mixing jet can be deduced. The estimated uncertainty of the reported concentration measurements is approximately ±5% on a mass fraction basis.