Acoustic Pressure Measurements in High-Temperature Environment
Résumé
In order to measure acoustic pressure in flow ducts at temperature above 100°C or in combustion chambers, the use of high-accuracy condenser microphones is no longer possible due to the heat load damaging the delicate components. A possible mitigation is the remote placement of the microphone, with the sensor connected via a small diameter waveguide to the desired measurement location. Such a device (called ?microphone probe?) has been build and used by DLR Berlin for several years for the investigation of in-duct sound fields at elevated pressure and temperature. However, there are certain calibration procedures and corrections required to account for the probe design. An experimental test series has been made to assess the probe characteristics. Special focus was set on the influence of the extension of the waveguide, which shall reduce the detrimental effect of reflections on the measured signal. Tests included a comparative calibration and high temperature and high pressure testing. The results are compared to a one-dimensional model of the probe design.
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