Temperature Measurements in a Shock Tube Using Laser-Induced Grating Spectroscopy

Abstract

To investigate structures of space transportation systems under reentry conditions, high-speed and high-enthalpy flows are simulated experimentally at the Institute for Thermodynamics at the University of the Federal Armed Forces Munich. To characterize flow conditions of the piston-driven shock tunnel, High-Enthalpy Laboratory Munich, laser-induced grating spectroscopy was chosen as the temperature measurement technique. In former works, it was shown that this technique is suited for the investigation of gas properties under single-shot conditions. In this work, single-shot measurements in a conventional medium-enthalpy shock tube are presented. For this purpose, the exact synchronization of the test bench with the optical setup was realized. Successful measurements at Mach numbers between approximately 1.4 and 2.2 leading to temperatures up to 840 K and pressures up to 2 MPa are presented. An additional test series was conducted to analyze the reproducibility of the measurements. A standard deviation of 3% was calculated for this investigated condition. The experiments were conducted in air, and a number of them were seeded with nitric oxide to improve the signal quality of the thermal grating.