Predicted Mass-Fraction and Concentration Distributions for Subsonic Turbulent Mixing Flow Based on Stagnation and Static Pressure and Temperature Measurements

Abstract

The mass-fraction distributions of an injectant and individual air species across and along the turbulent-flow mixing region formed by the local release of the injectant from a pipe into surrounding subsonic co-flowing air are predicted from experimental measurements obtained from three intrusive probes mounted closely together on a conventional traversing test rig. A standard pitot-tube probe is incorporated to measure both the stagnation and static pressures (P0, ps), a second probe measures the stagnation temperature (T0), and a third probe measures the static temperature (Ts). These four measurements (P0, ps, T0, Ts) are repeated at various radial and axial mixing-region locations. These measurements are combined with a special gas-dynamics analysis to provide a comprehensive method of determining the mass fractions of the injectant and air species, molecular weight and specific-heat ratio of the gas mixture, subsonic flow speed, flow Mach number and flow density at each traversing-rig measurement location. These gas-mixture and subsonic-flow properties are predicted at each local point in the mixing region by using a set of algebraic equations from classical gas dynamics. The type and number of measurements are just sufficient to provide a unique solution. For mixtures consisting of the injectant helium in a subsonic co-flowing air stream, the results of the present method are in good agreement with experimental or test data which is obtained from the numerically modeling the three-dimensional turbulent mixing flow in a wind tunnel with instruments, by using the Vulcan computational code from NASA.