Experimental Research in Non-equilibrium Thermochemistry Diagnosis of High Enthalpy Flow Field

The diagnosis of the thermochemical non-equilibrium state of the high enthalpy flow filed is an important method to analyze the thermodynamics of the hypervelocity aircraft. Tunable diode laser absorption spectroscopy (TDLAS) can realize non- intrusive measurement of high enthalpy flow filed. Firstly, based on FD-21 high enthalpy shock tunnel of China Academy of Aerospace Aerodynamics (CAAA), NO and H2O absorption spectrum measurement system were built, and the setting details and calibration method of the TDLAS were introduced. Subsequently, the measurement error of the TDLAS system was calibrated based on stagnation gas, and the overall error was within 2%. Finally, a series of TDLAS measurement experiments were carried out in the FD-21 high enthalpy shock tunnel, and such as flow filed pitot pressure, flow field static temperature, NO pressure and flow field velocity were obtained. The results show pitot pressure has the consistent trend with static temperature and NO pressure measured by TDLAS. In the two experiments, the deviation of the static temperature is 3.3%, the deviation of the NO pressure is 8.2%. The average speed of the two experiments was 2487 m/s and 2523 m/s respectively. The FD-21 high enthalpy shock tunnel has good flow filed repeatability. Further compared with experiment and calculation results, the thermochemical non-equilibrium process is discussed, and the origin are analyzed.