Detailed Experimental Survey of the Transonic Flow Field in a Rotating Annular Turbine Cascade

Abstract

An annular cascade of turbine profiles was tested in the wind tunnel for rotating cascades at DLR, Goettingen. In this facility investigations of the relative flow through a rotor cascade were done while the absolute inlet flow is purely axial and the relative inlet flow is determined by the circumferential speed of the rotor corresponding to the velocity triangles. Detailed experimental research concerning the 3-D flow field was carried out using an L2F-velocimeter and pneumatic probes; the flow field under investigation was determined by the isentropic downstream Mach number at midspan (Ma/2is &#61 1.1). First, at midspan local flow quantities (mean velocity, angle, Reynolds shear stress, turbulence intensity) were obtained using laser velocimetry. Additionally the static pressure on the blade surface was determined at 48 positions. The homogeneous flow quantities (velocity, flow angle, losses) were taken at four axial.