On Using Fast Response Pressure Sensors in Aerodynamic Probes to Measure Total Temperature and Entropy Generation in Turbomachinery Blade Rows

Abstract

This contribution addresses the possibility of exploiting the temperature dependency of piezoresistive sensors as a temperature measurement per se. This requires the characterization of the sensor, or the probe as a temperature probe, i.e., determination of the recovery factor between the sensor temperature and the flow temperature. This temperature calibration as well as the determination of the thermal response time was performed for two probe geometries: a high temperature flushmounted and a low temperature subsurface mounted single sensor total pressure probe, both with a probe head diameter of 2.5 mm. Two applications are reported. The first application was performed with the flushmounted sensor probe in the highspeed 312stage axial compressor CREATE tested in the 2 MW test rig of LMFA at أ‰cole Centrale de Lyon, in France. The probes were traversed at each interrow section up to temperatures of 180آ°C and an absolute pressure of 3 bar. The second application was performed with the subsurface mounted sensor probe in the highspeed single stage R4 compressor test rig of the von Karman Institute in Belgium. Both applications have shown results in extremely good agreement with simultaneous total temperature measurements with a Kieltype thermocouple probe. They also underline the necessity of a very accurate temperature calibration. Finally, considering the fact that a simultaneous temperature measurement can be obtained at the same location as the pressure measurement from the sensor, it is possible to derive entropy generation after a blade row, based on the average pressure and temperature quantities. This unveils another extremely interesting aspect of using the fast response probe technique in turbomachinery applications.