DESIGN AND DEVELOPMENT OF A FIVE-HOLE PROBE CALIBRATOR AND TRAVERSE TO INVESTIGATE INGESTION IN ROTATING CAVITIES OF HP COMPRESSORS

The internal air system is essential within aero-engine HP compressors for cooling and controlling blade tip clearances. Reducing the amount of air diverted from the main flow to the internal system improves the overall thermal efficiency, and so there is a need to understand the interactions of the flow within the compressor cavities. This paper describes the implementation and use of miniature five-hole probes to investigate the ingress and egress of the bore flow in an established engine representative test rig. The development of an inexpensive but accurate automated calibration device to calibrate different shaped probes over a wide range of pitch and yaw angles is described. The Reynolds number of the calibration flow was matched to the operating conditions of the pressurised test rig. A bespoke traversing mechanism was designed and installed within the shaft of the rig. The traverse enables the probe to move axially across one cavity, radially from the shaft to low cavity region and rotate to align with the local flow direction. Velocity data from a single commissioning test case at Ro = 0:65, Re-z = 5:5 x 10(4), Re q = 1:6 x 10(6), beta Delta T = 0:37 is presented. A Monte Carlo uncertainty analysis of the calibration and data collection procedure was conducted to validate the use of a five-hole probe for axial, tangential and radial velocity measurements in rotating cavities.