Design and Commissioning of a Supersonic Linear Compressor Cascade Test Section in the VKI Isentropic Compression Tube CT-2 Facility

A new supersonic linear compressor cascade test section, designed to investigate supersonic aerodynamics of low-pressure compressor and fan blades of forthcoming aircraft engine architectures, is presented in this paper. This test section, installed in the short-duration VKI isentropic compression tube CT-2 facility, is composed of a 5-blade linear cascade and is designed to operate from subsonic up to supersonic (M1 = [0.5–1.4]) inflow conditions with independent Reynolds number variation up to engine-like conditions. A throttling mechanism allows the variation of the cascade pressure ratio for a fixed inlet Mach number, thereby aiming to cover a wide flow regime from unstarted to started “unique incidence” conditions. The first section of the paper outlines the design of the test section flow path in view of the challenges imposed for the assessment of the aerodynamic performance of supersonic compressor blade profiles at engine-like conditions in a linear cascade arrangement. The theoretical optical setup designed for the Background-Oriented Schlieren (BOS) technique, used for the visualization of the complex shock patterns, is also outlined. The second section of the paper provides a numerical validation of both the test section flow path design and the optical path of the BOS setup. Particular attention is given to the validation of the throttling mechanism that allows for various back pressures at fixed inlet conditions, while optimizing blade-to-blade periodicity. In the final section of the present paper, a selection of preliminary experimental results obtained at high inlet Mach number (M1 = 1.21) are briefly presented. The observed shortcomings of the current iteration of the test section are discussed and possible improvements are presented. Finally, the BOS technique proved to be an invaluable tool for the visualization of the complex shock patterns and for the qualification of the cascade inlet and outlet flow.