High-speed Measurement of Vibrational and Rotational Temperatures of Nitrogen Molecules behind Hypervelocity Shock Wave by CARS Method

抄録

In the re-entering phase of space vehicle into the atmosphere strong shock wave is generated in front of the hypersonic vehicle, and high enthalpy flow with radiating, non-equilibrium real gas effects is generated behind the shock wave. As well as usual convecting heat transfer, the radiative and non-equilibrium real gas heating from the shock-heated air ahead of the vehicle plays an important role on the total heat flux to the wall surface, which affects the heat shield design of the re-entering vehicle. As for the research of such non-equilibrium high enthalpy flows behind strong shock waves, several spectroscopic studies have been reported by using shock tubes or shock tunnels. The direct measurement, however, of molecular vibrational/rotational temperatures from ground state, has not been performed, and the experimental data are in quite insufficient conditions. In this paper nonlinear spectroscopic measurement is performed on the vibrational/rotational temperatures of nitrogen behind the hypervelocity shock waves from 4-5km/s by CARS method. The CARS spectroscopic signals have been successfully observed by free-piston, double-diaphragm shock tube experiments, and the measured results are compared with the simulated spectra to decide the temperatures by spectral fitting method.