An axial-flow compression system dynamic model: Model development and validation

A quasi-1D, compressible-flow dynamic model is developed for the nonlinear stability analysis of high speed/pressure-rise compression systems. In particular, this model uses physical lengths of the components coupled with linear first-order time lags to model the compressor's dynamic lag. A semi-explicit Differential-Algebraic-Equation system resulted from a quasi-first-order approximation for state variable distributions in the lumped volumes. Through nonlinear stability analysis, the model is able to predict the experimentally observed hysteresis. The compressible-flow model provides more accurate modeling results than the incompressible-flow model even for low-speed data. The model was also able to predict the bifurcation points located in the negative-sloped portion of the characteristic, which can not be predicted by incompressible-flow models. Compressor wheel speed was concluded to have a strong effect on the bifurcation diagrams of other system parameters and the qualitative difference between low-speed and high-speed bifurcation sets for several parameters gives the conclusion that Greitzer's B parameter should not be used to characterize high-speed compression system stability.