Abstract:
Compression systems used in the power generation plants and aerospace propulsion
applications are prone to the aerodynamic instabilities of stall and surge. Both of these
instabilities result in reduced off-design of the compressors, and raise safety concerns.
This research focuses on the analysis of surge phenomena in axial flow compressors.
Mathematical model developed by Moore and Greitzer (1985, 86) [1, 2] has been used for this
purpose. The axisymmetric compressor characteristic employed by the Moore-Greitzer Model
has been generalized to study the effect of the parameters involved over a wider set of values.
The pure surge case of the Moore-Greitzer Model is then subjected to Method of Multiple Time
Scales (MTS), and a closed-form solution has been obtained for the problem.
Subsequent application of Bifurcation theory on the closed-form solution reveals that
surge manifests itself as a sustained Limit Cycle Oscillation (LCO) subject to fulfillment of a
necessary condition dictated by the compressor characteristic. It has been found that the
behaviour of surge oscillations is significantly dependent upon the choice of compressor
characteristic.
From combination of the various parameters involved in the Moore-Greitzer Model, two
new parameters have been obtained, and the condition for the stable limit cycle oscillations has
been obtained, which revolves around these parameters.
The analytical solution has been verified against the numerical simulation of the Moore Greitzer Model, thus implying that Method of Multiple Time Scales has successfully captured
the qualitative and quantitative aspects of the surge phenomena.
viii
The results of the analyses presented in this research work can provide useful
guidelines to the turbomachinery designers in developing a better understanding towards the
surge problem and in improving off-design performance of axial compressors.
