EXPERIMENTAL ANALYSIS OF AN AXIAL COMPRESSOR OPERATING UNDER FLOW DISTORTION

In aircraft engines, compressor stages can encounter situations in which the flow is distorted at rotor inlet, for example during particular flight maneuvers, or due to the shape of the inlet of the airframe. The main objective of this paper is to investigate experimentally the effect of an inlet flow distortion on the internal flow dynamic and its consequences on the performance and operability of these machines. The distortion was generated by a porous plate grid installed upstream of the compressor. Eight total pressure rakes placed downstream of the grid were used to evaluate the distortion. Unsteady pressure measurements were performed on the casing at different axial and azimuthal positions to investigate the dynamic flow behavior at nominal conditions, at an operating point close to stall and during the transition to stall. 2D-2C PIV maps, synchronized with the runner position, were obtained on rotor blade-to-blade planes at three different spanwise positions (79%, 51%, 18% of the blade span). Three relative angular positions of the grid to the laser sheet were investigated at two different flow rates, namely the nominal flow rate and a flow rate close to stall. These three positions are corresponding to the laser sheet cutting through i/ the center of the grid's wake and ii/ the two edges of the grid. The impact of the distortion on the performance of the compressor is analyzed and compared to existing models. The impact of the flow dynamic will also be considered, especially in operations close to the stall limit.