Aeromechanical Control of High Speed Axial Compressor Stall and Engine Performance—Part II: Assessments of Methodology

Abstract

A theoretical assessment was made explaining how aeromechanical feedback control can be implemented to stabilize rotating stall inception in highspeed axial compression systems. Ten aeromechanical control strategies were quantitatively evaluated based on the controltheoretic formulations and dimensionless performance analysis outlined in the Part I companion paper (McGee and Coleman, 2013, “Aeromechanical Control of HighSpeed Axial Compressor Stall and Engine Performance—Part I: ControlTheoretic Models,â€‌ ASME J. Fluids Eng., 135(3), p. 031101). The maximum operating range for each aeromechanical control scheme was predicted for optimized structural parameters. Predictability and changeability in the hydrodynamic pressure, temperature, density, operability, and aeromechanical performance of dynamicallycompensated, highspeed compressor maps of corrected pressure, corrected mass flow, corrected speeds, temperature ratios, and optimum efficiency were compared for the various aeromechanical control strategies. Compared with dynamicallycompensated, lowspeed compressor maps of pressure rise and flow coefficient (Gysling and Greitzer, 1995, “Dynamic Control of Rotating Stall in Axial Flow Compressors Using Aeromechanical Feedback,â€‌ ASME J. Turbomach., 117(3), pp. 307–319; McGee et al., 2004, “Tailored Structural Design and Aeromechanical Control of Axial Compressor Stall—Part I: Development of Models and Metrics, ASME J. Turbomach, 126(1), pp. 52–62; Frأ©chette et al., 2004, “Tailored Structural Design and Aeromechanical Control of Axial Compressor Stall—Part II: Evaluation of Approaches,â€‌ ASME J. Turbomach., 126(1), pp. 63–72), the present study shows that the most promising aeromechanical designs and controls for a class of highspeed compressors were the use of dynamic fluid injection. Dynamic compensations involving variable duct geometries and dynamicallyrestaggered IGV and rotor blades were predicted to yield less controllability under highspeed flow environments. The aeromechanical interaction of a flexible casing wall was predicted to be destabilizing, and thus should be avoided in highspeed compression systems as in lowspeed ones by designing sufficiently rigid structures to prevent casing ovalization or other structurallyinduced variations in tip clearance.