Wide bandwidth stagnation temperature measurements in vortical flows behind turbine vanes

A new fast response measurement technique for total temperature, originally developed for testing in transient facilities, has been adapted and used to make turbine vane wake flow measurements in a continuously running linear cascade. The bandwidth of the new method approaches 100 kHz, and is a considerable improvement on previous techniques. The measurements show clear evidence of vortex shedding over a range of Mach numbers. The shedding is consistent with previous schlieren and wake pressure measurements. At sub-sonic exit Mach numbers, the total temperature data shows vortex shedding at a Strouhal number of just above 0.2. This is consistent with data from other cascades. At supersonic exit conditions, the measurements show that the vortex shedding breaks down into a number of different intermittent shedding modes. This is also consistent with earlier results. The existence of strong vortex driven energy separation in the wake through the Eckert-Weise effect, in which temperatures are suppressed in the centre and discrete `hot spots´ appear towards the edges of the wake flow, is confirmed by the total temperature measurements. The new measurements are used to explain earlier results from the cascade, which were previously thought to be anomalous