A cascade tunnel for investigation of rotating stall

Abstract

A test apparatus which will reproduce the rotating stall phenomenon found in axial compressors has been constructed and installed in the main wind tunnel circuit of the Gas Turbine Laboratory. The test section consists of a two dimensional, circular, radial outflow cascade between two flat plates. The cascade was designed to reproduce the pressure distribution, and hence the stall characteristics, of a typical rectilinear cascade. The air entry angle to the cascade is controlled by a variable angle nozzle ring so that the cascade may be stalled and unstalled in operation, Provision has been made for removal of wall boundary layers by suction, and for changing the setting of the cascade stagger angle. By a simple modification, the blades may be supported elastically to permit torsional vibrations. Independent variation of the Reynolds number and Mach number of the air stream is possible. Visual observations of the flow using Schlieren and Interferometer equipment can be made through windows in the walls of the test section. In preliminary tests, rotating stall has been observed and the research program will commence in August of 1954.