Dynamical Study of Surge Behavior in Axial Flow Compressors

Der-Cherng Liaw, Li-Feng Tsai

Axial flow compressor, bifurcation, stability.

It is known that two types of unstable phenomena might occur while the compressor operates near its maximum achievable pressure rise. Those might limit the operation of gas turbine jet engines. Under either one of the two unstable conditions, a moderate disturbance can result in system instability so that the compression system might either experience a large amplitude oscillation (corresponding to the so-called surge) or jump into a very inefficient operation at constant mass flux and low pressure-rise (corresponding to the so-called stall). In a previous study (Liaw and Abed, 1996), we had presented the study of stall behaviour in axial flow compressors by using Moore-Greitzers model proposed in 1986. Not only the condition for the occurrence of stall wave was derived, a quadratic type control law was also proposed to prevent the appearance of stall in compressor dynamics. In this paper, we extend those results to focus on the study of surge behaviour by using the same model without considering the dynamics of stall wave. Conditions for local stability and non-local dynamical behavior of axial flow compressor are analytically obtained by using system linearization and bifurcation theorem. Numerical results will also be presented to show the linkage between bifurcation phenomena and system instabilities.