Time resolved measurements in the Durham Cascade

Abstract

This paper describes investigations into unsteady flow phenomena in a high turning linear cascade with a nominal steady flow. Traditionally time averaged instrumentation is used in such a cascade. Detailed intermittency readings were taken inside the cascade using hot wires to highlight the detailed flow interactions of the passage vortex and the blade suction surface. A new fast response five hole probe was built and tested against a hot-wire. Time-accurate measurements taken using this probe allowed an evaluation of the error made by using a probe with limited frequency response for the cascade measurements. This evaluation showed significant deviations in loss for regions of high unsteadiness, for instance the passage vortex. The Reynolds stress tensor was measured at 101%, 115% and 128% axial chord and the deformation work was calculated for 126% axial chord. The deformation work shows regions of negative values and positive values. While negative values are associated with a production of turbulent k.e. from the mean kinetic energy, positive values may represent a gain of kinetic energy from the turbulence.