Pressure, Temperature, and Velocity Measurement of Supersonic Flows Using TDLAS with Triangular Laser Beam Path

Abstract

This study presents tunable diode laser absorption spectroscopy techniques for simultaneous measurement of pressure, temperature, and velocity of supersonic flows. A triangular laser beam path is proposed to facilitate single-side installation of the tunable diode laser absorption spectroscopy system, velocity measurement in the passage with parallel side walls, and signal amplification by enhancing laser path length in the flow. Flow properties such as pressure, temperature, and velocity are determined from a single absorption line through a proposed spectroscopic analysis procedure. To demonstrate the proposed techniques, a tunable diode laser absorption spectroscopy system that detects an absorption line of molecular oxygen is utilized, and supersonic air flows are generated using a shock tunnel and a blow-down type wind tunnel. Through shock tunnel and wind tunnel testing, it is confirmed that the proposed tunable diode laser absorption spectroscopy techniques can be used for supersonic flow diagnosis.