Temperature Measurement in High-Enthalpy Flow by NO Laser-Induced Fluorescence

Due to real-gas effect, the studies of hypersonic phenomena still rely on experiments. Temperature, one of the key parameters of the flow-field, can only be acquired by optical diagnostics. However, as there are challenges from many aspects, few works regarding measurements in high-enthalpy flow have been reported. This paper presented the laser-induced fluorescence (LIF) investigation of high-enthalpy flow generated by JF-10, a H₂/O₂-detonation-driven shock tunnel. A LIF system was established for the impulsive testing facility, and nitric oxide (NO) was chosen as the fluorescent species. Since the testing environment is harsh for LIF measurement, adjustments have been made on the conventional planar LIF technique. The excitation planar beam was made parallel to the direction of the detector, thus the fluorescence signal was concentrated, and clear LIF images were taken. By two-line thermometry (TLT), the rotational temperature of NO molecules in the free stream at the test section was acquired, and thus the translational and rotational temperature of the flow was determined. The result shows that the translational and rotational temperature of the test flow is 600 K.