TDLAS-based investigation on thermal parametric shifting caused by air vitiation in hypersonic test

Abstract

Combustion heated wind tunnel has been widely used for hypersonic ground tests. Unfortunately, it will inevitably introduce component(mainly water vapor and carbon dioxide) different from atmospheric air, which leads to uncertainties in results of the wind tunnel test. Tunable diode laser absorption spectroscopy, as a high-speed and non-intrusive technique which allows combined measurement of selected gas concentration, temperature and velocity, has shown great potential and advantages in this area. An experimental investigation on the vitiation effects of hypersonic testing was carried out with focus on TDLAS measurement. The experiments were conducted in a shock tunnel with which various strengths of shock waves as well as mole fractions of contaminations to simulate the related combustion-heated wind tunnel flow conditions. There are three main aspects: 1. Static temperature is measured in the isolator of the direct-connect combustion facility under different flow conditions; 2. Static temperature is obtained on the model flow under different vitiation levels; 3 The temperature in the nozzle exit can be monitored by TDLAS in different flow conditions, which may be helpful to understand the phenomenon of steam condensation. In summary, this paper attempts to study the thermal parametric shifting in the shock tunnel, aiming to portray the vitiation effect in a systematical way.