Determination of the Pressure Distribution and Fluctuations of the Transonic Flow in a Highly Loaded Compressor Cascade

In-depth analysis of secondary flow phenomena is essential for active flow control investigations for highly efficient aero engines. Therefore a linear stator cascade test facility for high speed flow conditions was established at the Institute of Aeronautics and Astronautics of the Technische Universitat Berlin. Center piece of the research is a linear cascade consisting of seven controlled diffusion airfoils featuring high loading and increased deflection. The design point is set to a Mach number of M = 0.75 and a Reynolds number of Re = 1.1·10^6 based on the axial chord. The center blade is equipped with high frequency, flush mounted pressure transducers that can be traversed perpendicular to the flow. This setup allows high spatial and temporal resolution of the blade pressure distribution and its fluctuations hence giving detailed information about three-dimensional secondary flow phenomena over the whole blade height. Furthermore an analysis of the base flow by oil flow pattern supports the understanding of the flow structures detected with the sensor equipped blade. The main and secondary flow structures are investigated on the suction and pressure side under variation of incidence angle and inflow Mach number. The pressure distribution and its standard deviation give knowledge about the profile and secondary flow losses that are depending on size and intensity of the separation and the corner vortices. The analysis of the frequency spectrum of the static profile pressure shows flow structures like separation and shocks and their characteristic frequencies.