Bridging the gap between high-speed linear cascades and rotating turbine facilities

Abstract

This paper presents the design, instrumentation, and commissioning of a novel measurement tool for testing turbomachinery components, specifically targeted to transonic rotors. This tool enables high-resolution investigation of complex 3D rotating geometries in the stationary frame, addressing the scarcity of relevant transonic facilities capable of precise aerodynamic diagnostics. The presented testing solution bridges the gap between the well-established linear cascades and rotating rigs enabling high-resolution measurements and optical access in an annular cascade comparable to what is standard practice in low-speed linear cascades. Conversely, high-speed rotating rigs are typically limited to torque and power measurements due to the small airfoil size and restricted access. A flow conditioning gauze with hundreds of radial and circumferential blades replicates the total pressure and whirl angle profiles experienced by the rotor in its relative frame at transonic conditions. Gauze placement was optimized using 3D Reynolds-Averaged Navier-Stokes simulations to ensure homogeneous inlet conditions. The final hardware was machined in stainless steel to withstand elevated temperatures. Inlet flow quality was verified with total pressure probes and static taps around the annulus. Downstream of the gauze, total pressure, whirl angle, and Mach number profiles were measured using Kiel and five-hole probe traverses, confirming agreement with design targets and validating this configuration for turbomachinery testing. The rig supports both sector and full-annular cascade configurations, including single and rainbow geometries. Tests can exceed 30 min, enabling high-resolution, full-annulus traverses. Exit Reynolds numbers range from 30,000 to 4,000,000, with independently adjustable pressure ratios allowing testing from subsonic to supersonic conditions.