CHALLENGES IN THE APPLICATION OF HOT-WIRE ANEMOMETRY FOR THE INVESTIGATION OF TRANSIENT TEMPERATURE FLUCTUATIONS IN A HIGH-SPEED RESEARCH COMPRESSOR

This paper presents an investigation into the principles of unsteady total temperature measurement with a parallel hot-wire while also examining potential challenges that might occur when using a custom-made hot-wire in a High-Speed Research Compressor. After modifying the institute´s open free-stream calibration tunnel with a pressure chamber to enable the calibration of hot-wires at compressor-representative conditions, different approaches for extracting the total temperature from the hot-wire raw data were evaluated. The comparison of the’optimized King’s law’,’Lienhard & Helland method’ and a new polynomial approach revealed reasonable results with similar accuracy, whereas the polynomial concept requires less calibration effort. When measuring with the hot-wire in the research compressor, significant disturbances were caused due to vibrations. After several mechanical modifications at the prongs, probe holder and probe guidance, followed by a visual inspection with a high-speed camera, it was concluded, that wire strain gauging occurred due to prong vibrations. This difficulty could be avoided by welding the wires with less tension and a noticeable slack. Finally, the effect of wire contamination was investigated. After two hours of testing, particle accumulation shows potential of having a significant effect on the measurement results in open-loop test rigs.