CALIBRATION OF A 4-HOLE PYRAMID PROBE AND AREA TRAVERSE MEASUREMENTS IN A SHORT-DURATION TRANSONIC TURBINE CASCADE TUNNEL

A four-hole pyramid probe has been calibrated for use in a short-durat ion transonic turbine cascade tunnel. The probe is used to create area traverse maps of total and static pressure, and pitch and yaw angles of the flow downstream of a transonic annular cascade. This data is un usual in that it was acquired in a short-duration (5 s of run time) an nular cascade blowdown tunnel. A four-hole pyramid probe was used whic h has a 2.5 mm section head, and has the side faces inclined at 60 deg rees to the flow to improve transonic performance. The probe was calib rated in an ejector driven, perforated wall transonic tunnel over the Mach number range 0.5-1.2, with pitch angles from -20 degrees to +20 d egrees and yaw angles from -23 degrees to +23 degrees. A computer driv en automatic traversing mechanism and data collection system was used to acquire a large probe calibration matrix (approximate to 10,000 rea dings) of nondimensional pitch, yaw, Mach number, and total pressure c alibration coefficients. A novel method was used to transform the prob e calibration matrix of the raw coefficients into a probe application matrix of the physical flow variables (pitch, yaw, Mach number etc.). The probe application matrix is then used as a fast look-up table to p rocess probe results. With negligible loss of accuracy, this method is faster by two orders of magnitude than the alternative of global inte rpolation on the raw probe calibration matrix. The blowdown tunnel (me an nozzle guide vane blade ring diameter 1.1 m) creates engine represe ntative Reynolds numbers, transonic Mach numbers and high levels (appr oximate to 13%) of inlet turbulence intensity. Contours of experimenta l measurements at three different engine relevant conditions and two a xial positions have been obtained. An analysis of the data is presente d which includes a necessary correction for the finite velocity of the probe. Such a correction is non trivial for the case of fast moving p robes in compressible flow.