A method of characteristics approach to the problem of supersonic flow past oscillating cascades with finite blade thickness

A method of characteristics approach is described for the computation of supersonic flow past oscillating cascades having blades of finite thickness distribution. The transonic small disturbance equation is solved for cascades with subsonic leading-edge locus. Sample calculations are presented for the inlet and passage flow and comparisons are given with calculations for flat-plate cascades and available measured pressure distributions. (Author)Prepared for: Chief of Naval Researchhttp://archive.org/details/methodofcharacte00vogeSupported by the Office of the Naval Research through the Naval Postgraduate School Research Foundation ProgramN

GT2006-90214 UNSTEADY AERODYNAMIC BLADE EXCITATION AT THE STABILITY LIMIT AND DURING ROTATING STALL IN AN AXIAL COMPRESSOR

ABSTRACT The stable operating range of axial compressors is limited by the onset of rotating stall and surge. These flow conditions endanger the reliability of operation and have definitely to be avoided in compressors of gas turbines. However, there is still a need to improve the physical understanding of these flow phenomena to prevent them while utilizing the maximum available working potential of the compressor. This paper discusses detailed experimental investigations of the rotating stall onset with the main emphasis on the aerodynamic blade excitation in the Dresden four-stage LowSpeed Research Compressor. The stall inception, which is triggered by modal waves, as well as the main flow features during rotating stall operation are discussed. To investigate the unsteady pressure distributions, both the rotor and the stator blades of the first stage were equipped with piezoresistive pressure transducers. Based on these measurements the unsteady blade pressure forces are calculated. Time-resolved results at the stability limit as well as during rotating stall are presented. For all operating conditions rotor-stator-interactions play an important role on the blade force excitation. Furthermore the role of the inertia driven momentum exchange at the stall cell boundaries on the aerodynamic blade force excitation is pointed out