Total Pressure Correction of a Sub-miniature Five-hole Probe in Areas of Pressure Gradients

Five-hole probes, being a dependable and accurate aerodynamic tools, are excellent choices for measuring complex flow fields. However, total pressure gradients can induce measurement errors. The combined effect of the different flow conditions on the ports causes the measured total pressure to be prone to a greater error. This paper proposes a way to correct the total pressure measurement. The correction is based on the difference between the measured total pressure data of a Kiel probe and a sub-miniature prism-type five-hole probe. By comparing them in a ducted fan related flow field, a line of best fit was constructed. The line of best fit is dependent on the slope of the line in a total pressure versus span and difference in total pressure between the probes at the same location. A computer program, performs the comparison and creates the correction equation. The equation is subsequently applied to the five-hole probe total pressure measurement, and the other dependent values are adjusted. The validity of the correction is then tested by placing the Kiel probe and the five-hole probe in ducted fans with a variety of different tip clearances. ∗Graduate Research Assistant, ASME Student Member †Research Engineer, Currently at Siemens Energy, FL ‡Professor of Aerospace Engineering, ASME Fellow NOMENCLATURE CPT Coefficient of total pressure K Correction Slope Location Current spanwise location that data is found Location+1 Next spanwise location that data is found PT Total pressure Slope Slope of found between two data points Step Rotor span movement size UM Speed of the motor at midspan Greek δPT Change in total pressure due to gradient ρ Air density Subscript Corrected Corrected value Correction Correction value based on Slope and K Di f f erence Difference between probes exit Denotes area downstream of rotor FHP Denotes measurements taken by the five-hole probe in Denotes area upstream of the rotor at the inlet Kiel Denotes measurements taken by the Kiel probe Original Original measured value, before correction 1 Copyright c © 2012 by ASME