Measurement of acoustic pressure in high-temperature environment

A previous study by the authors has shown the rotation of the polarization plane of a laser beam due to fluid vorticity in a Rijke tube. The vorticity has been found to originate during the high-amplitude pressure oscillations in the tube. In the present study, the above principle is used to measure pressure in areas where sustained high temperature (1500–3000 K) of the gaseous medium creates problems in wall-mounted transducer-based measurements. The procedure to convert the measured vorticity into pressure has been discussed. The acoustic pressure has been found to follow a linear relationship with the percentage of leaked laser light through the analyzer for different heating durations of the Rijke tube. The time history of vorticity and acoustic pressure measured using a microphone have been found to correlate strongly. The method is also applied to measure pressure in a channel involving a propagating hydrogen–air flame and tulip inversion. The experimentally measured pressure history is found to be in close agreement with the numerical prediction. Theoretical analysis has been carried out to relate the vorticity generated due to pressure fluctuations.