Effects of non-axisymmetric endwall contouring and film cooling on the passage flowfield in a linear turbine cascade

Abstract

The time-resolved flowfield is measured in the passage of a linear turbine cascade to show the effects of endwall film cooling and non-axisymmetric endwall contouring on the passage secondary flows. A particle image velocimetry system is used in three measurement planes: the plane at the exit of the passage and two streamwise planes along the blade suction side. In the downstream half of the passage, the passage vortex moves away from the endwall toward the midspan, but closely follows the profile of the blade suction side. The secondary velocity vectors and vorticity fields in the passage exit plane indicate the large size of the passage vortex. The measured velocities in the streamwise measurement planes reveal the trajectory of the passage vortex as well as steep gradients in the direction normal to the blade surface. The passage vortex can also be identified by elevated flow unsteadiness as reported by turbulent kinetic energy levels. When passage film cooling is added, the size of the passage vortex, secondary velocities, and exit plane turbulent kinetic energy are all increased. Endwall contouring has the opposite effect, reducing the passage vortex size, the secondary velocities, and exit plane turbulent kinetic energy.