Experimental results for deep surge in a small single-stage centrifugal compressor are compared to predictions based on the lumped parameter Greitzer model developed for axial compressors. Both negative and positive flow branches of the steady characteristic, being essential for the model, were measured. Predictions are in fair agreement with data when using a relaxation time smaller than the one proposed for axial compressors. The stability limit of the model equations have been studied for finite amplitude disturbances.

discrepancies between model and data appearing particularly near and after times of flow reversal (see m c (t) in Figs. 2(a) and 3(a), may be explained by the incompressibility assumption in the momentum balance for the compressor ducting, equation (la). Here, sample calculations have shown that the ignored terms involving the time-rate-of-change of mass in the ducting may amount to as much as 25 percent of the terms retained. The fact that the time periods, during which the ignored terms are significant, are short, however, may explain why the model results are still useful.