POROUS PRESSURE-SENSITIVE PAINT FOR MEASUREMENT OF UNSTEADY PRESSURES IN TURBOMACHINERY

This work details the development and application of porous pressure-sensitive paint (PSP) for measuring unsteady surface pressures in turbomachinery. The advantages of porous PSP over conventional methods include global pressure measurement, fast response time, and instrumentation of thin turbomachinery components that are otherwise difficult or impossible to instrument. In this paper, the development, calibration, and application of porous PSP to turbomachinery are discussed. Porous PSP formulations were developed to ensure fast response times and good adhesion characteristics to rotating parts. Experimental methods such as phase-locking and image registration were developed to acquire quality data. Dynamic response calibrations of PSP with a fluidic oscillator were performed, indicating that porous PSP formulations have a response time of up to 40 kHz. For a turbomachinery application, the inlet wall and impeller blades of a turbocharger compressor were painted with fast-responding polymer/ceramic PSP. The turbocharger was operated at 100,000 rpm, corresponding to a blade-passage frequency (BPF) of 10 kHz. Even at this high speed and BPF, porous PSP was able to resolve the unsteady wall pressure distributions about the blade. In addition, a flow blockage was created to induce an inlet flow distortion on the compressor. Porous PSP was able to resolve the 1.67 kHz unsteady blade loading. Potential applications of porous PSP to unsteady turbomachinery testing include evaluations of rotor/stator interaction, flutter, inlet flow distortion, rotating stall, and surge.

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