11th European Conference on Turbomachinery Fluid dynamics & Thermodynamics
The experimental characterization of the rotating stall phenomena appearing in a single-stage high-speed low-pressure axial compressor is presented in this paper. The compressor design is representative of an advanced direct drive turbofan booster. The stage is equipped with both fast response and steady instrumentation. Fast response pressure sensors are placed in the rotor casing and in the hub at the outlet of each row. The former are employed to perform a detailed survey on the tip leakage flows, and the latter allow to determine the extension of the stall cells across the stage. A fast response aerodynamic pressure probe is located at the rotor outlet to detect the size of the stall cells. The global performances of the machine are recorded by time-averaged measurements at the inlet and at the outlet of the stage. Tests recording the stall inception and the complete stall transients are performed at different speed lines in the VKI-R4 closed loop compressor test rig. The inception mechanism is determined by the comparison between the time mean and the time-resolved data. In terms of stall inception, the compressor exhibits long length scale at lower rotational speed and an abrupt stall at higher rotational speed. The characterization of the stall cells is performed in terms of number, size, and speed by using the unsteady data acquired with the fast response instrumentation. The compressor presents a single full span stall cell in all the speed lines investigated.