A previous small-perturbation analysis of circumferential waves in centrifugal compression systems, assuming inviscid flow, is first shown to be consistent with observations that narrow diffusers are more stable than wide ones, when boundary-layer displacement effect is included.
Then, a previous analysis for finite-strength transients containing both surge and rotating stall in axial machines is adapted for a centrifugal compression system. Under certain assumptions, and except for a new second-order swirl, the diffuser velocity field, including resonant singularities, can be carried over from the previous inviscid, linear analysis.
Nonlinear transient equations are derived and applied in a simple example to show that throttling through a resonant value of flow coefficient must occur in a sudden surge-like drop, accompanied by a transient rotating wave. This “inner” solution is superseded by an “outer” surge response on a longer time scale. Numerical results are shown for various parametric choices relating to throttle schedule and the characteristic slope.