A Comprehensive View to Surge Frequencies and Stall Stagnations in Axial Flow Compressor Systems

Abstract

Essential features of compressor surge phenomena are found to be described by the following two non-dimensional parameters; a resonance excitation frequency and a surge frequency parameter. The former is the number of times of excitations by the system resonance frequency given to the fluid particle in the time required for the particle to pass through the whole flowpath, or, in short, the resonance frequency multiplied by the passing time. The latter is the number of surge cycles repeated in the particle passing time. When multiplied by corresponding Mach number of the compressor tip speed, both parameters become nearly independent of the compressor speeds. Both parameters construct numerical-experimentally a whole picture of the surge behaviors on the basis of simulation results. It shows the behaviors of surge frequencies and the stall stagnation limits affected by the resonance excitation frequency under the influence of various factors, such as flowpath configurations, relative locations of the compressor in the flowpath, numbers of compressor stages, compressor speeds and operating conditions, pressure ratios, etc. The growth or decay of surge actions and the stagnation occurrences are found to be controlled essentially by the resonance excitation frequency. For less than some specified value of the resonance excitation frequency, stall stagnations will occur. On the other hand, sufficient magnitude of the parameter value will develop deep surges. It could be employed also as a relatively simple and reasonable criterion for the stall-stagnation boundary.