Shock Tube Diagnostics Utilizing Laser Raman Spectroscopy

The laser Raman scattering technique shows potential as a diagnostic method for determining the chemical and thermodynamic state of high-temperature gases. To investigate the utility of this technique for shock-tube diagnostics, and to validate the method at known elevated temperatures, vibrational Raman intensities were measured behind an incident shock wave. Intensity history data through the wave front, vibrational excitation times of oxygen in air, along with temperature and density measurements for oxygen and nitrogen in air were obtained over a range of postshock conditions. The measured densities and temperatures were found to be in good agreement with shock-wave theory. An excitation time measurement also agreed well with shock-tube data obtained with other diagnostic methods. In general, the results indicated that the Raman scattering technique was accurate at elevated temperatures and should prove useful in determining the thermochemical state of gases in continuous flows as well as in shock tubes and other impulse facilities.