Generalized Multistage Axial Compressor Characteristics

Presented below is a method of calculating the off-design performance of multistage axial compressor characteristics that differs in concept from previous methods. A set of resulting calculations has certain general properties; namely, that it is independent of absolute stage work and flow coefficient, number of stages, and annulus geometry. The set depends only on a stage characteristic “shape” which is normalized so that the work and pressure coefficient is unity when the flow coefficient is unity. One set of tabulated results can be applied to many different designs. Two comparisons with experiment are presented below and the agreement is fairly good. An added benefit derived from this kind of general approach is that one gains physical understanding of the various regions of compressor operation. In this regard the concepts of “axial equilibrium” and “match point” have been developed which in the present context are defined in a precise, quantitative manner.