Engineering Application of Oxygen Laser-Induced Fluorescence Temperature Measurements in Aerodynamic Flows

Abstract

Oxygen laser-induced e uorescence was studied experimentally to quantify signie cant error and uncertainty sources and to evaluate the technique feasibility for gas temperature measurements in the 1 ‐6-atm, 300‐500-K regime. The dominant uncertainty source is quantum noise. For low-speed e ows, the dominant error source is nonlinear process errors originating from oxygen ion e uorescence and saturation. For e ows where the pressure is unknown or variable, collisional quenching may introduce an additional error up to 3 K/atm. For high-speed e ows above 300 K, the dominant error source is the slow vibrational relaxation time of oxygen molecules. The optimum experimental conditions are determined by budgeting the allowable temperature inaccuracy to various uncertainty and error sources. In general, the nonlinear process errors limit the laser e uence that may be used, and the quantum noise determines the minimum number of laser shots per measurement.