Simultaneous Measurements of Velocity Vector and Temperature in Transonic Flow by Laser-Induced Fluorescence Method

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In the large-scale gas or steam turbine, the flow around the blade tip becomes transonic, and the shock waves are generated in the blade passage. These shock waves induce the boundary layer separation and the vibration of blades, which degrade the efficiency. To clarify these phenomena, the laser-induced fluorescence (LIF) method was applied for measuring the velocity and temperature of the transonic flow with atmospheric pressure. The obtained results were summarized as follows.1. The blow-down type transonic wind-tunnel was constructed, and the nozzle with rectangular cross-section was made to simulate the flow field in the transonic cascades. The LIF diagnostic system based on the argon-ion laser was also constructed.2. The prism was inserted into the resonance cavity of the argon laser to operate it with the broad-band mode. Under this condition, it was shown theoretically that the LIF intensity was inversely proportional to the temperature of the flow field. By using this, the three-. dimensional distribution of the temperature in the nozzle was measured. Also, by inserting a tunable etalon into the resonance cavity, the vertical mode of the argon laser was selected. This etalon was traversed by the stepping motor to obtain the spectral profile of the fluorescence. The velocity in the nozzle was calculated from the Doppler shift of the spectral peak of the fluorescence.3. The measured temperature and velocity were shown to agree very well with those obtained from the static pressure measurements.Present research proved that the temperature and velocity in the transonic flow-field near an atmospheric pressure could be measured with high accuracy by the LIF method.