The Unsteady Pressure Field Over a Turbine Blade Surface: Visualisation and Interpretation of Experimental Data

Abstract

The unsteady static pressure field over a turbine rotor has been measured in the Oxford Rotor Facility using 78 flush-mounted miniature pressure transducers. This extensive surface coverage allows ensemble-averaged data to be displayed as an animated image. At the mid-height plane the fluctuations are well predicted using the UNSFLO 2-D unsteady code: away from mid-height the data shows large fluctuations. 12 transducers mounted on the blade leading edge show the relative total pressure field entering the blade row; these plus area traverse measurements at rotor exit are used to interpret the surface flow features. Rotor-mounted hot wires show large variations in blade incidence during the wake-passing cycle and allow conversion of blade-relative data into the absolute frame. Large pressure fluctuations in the root region may be explained in terms of a loss core associated with the NGV wake.