Single / Dual Pump CARS Measurements in Vibrationally Relaxing Supersonic Mixing Layer

摘要

The paper presents effect of vibrational relaxation between a vibrationally excited supersonic flow and jet stream of a rapid vibration-translation (VT) relaxer. For the discharge excited supersonic flow of nitrogen up to T_V=2000 K, mixing of CO_2 downstream of the expansion corner results in the decrease of expansion angle by up to △θ = 8°, as a consequence of heat release during the vibrational relaxation and the resultant pressure rise by up to 55%. Single / dual pump Coherent Anti-Stokes Raman Scattering measurements demonstrated the decrease of the vibrational temperature across the mixing layer, which is accompanied with the increase of local CO_2 mixture ratio. A two-dimensional vibrational temperature distribution coincides with the spatial profile of the modified shear layer measured in the schlieren visualization. The region of the vibrational relaxation is also consistent with the layer of the VT relaxer penetration into the supersonic flow downstream of the trailing shocks, with the subsequent flow residence on the corresponding time scale of the VT relaxation.