Calibration of Multi Hole Pressure Probes for Three Dimensional Flow Measurements in Subsonic Flow*

Abstract

The calibration of two multi hole pressure probes with four and five pressure holes are presented at three Mach numbers, viz. M=0.3, 0.4 and 0.5. The calibration was carried out in a subsonic calibration tunnel in yaw angle and pitch angle range of ± 30° at 5° interval. Calibration curves are presented and compared at the three Mach numbers. Calibration data at one Mach number are used as calibration data and calibration data at other Mach numbers are used as measured data to find the flow parameters namely, total pressure and static pressure and flow yaw angle and pitch angle using a lookup table method at these Mach numbers. The interpolation errors are small when the yaw angle and pitch angle range is from -20° to 20° for the four hole probe and from -15° to 15° for the five hole probe. Mach number effects on the flow measurements can be incorporated using the iterative method presented. This method is used to obtain flow parameters in the wake of a steam turbine rotor tip cascade blade. The differences in the obtained values using calibration coefficients at three Mach numbers are found to be negligible.