No abstract

The surge and rotating stall post-instability behaviors of axial flow compressors are investigated from a bifurcation-theoretic perspective, using a model and system data presented by Greitzer (1976a). For this model, a sequence of local and global bifurcations of the nonliner system dynamics is uncovered. This includes a global bifurcation of a pair of large-amplitude periodic solutions. Resulting from this bifurcation are a stable oscillation (“surge”) and an unstable oscillation (“anti-surge”). The latter oscillation is found to have a deciding significance regarding the particular post-instability behavior experienced by the compressor. These results are used to reconstruct Greitzer’s (1976b) findings regarding the manner in which post-instability behavior depends on system parameters. Although the model does not directly reflect nonaxisymmetric dynamics, use of a steady-state compressor characteristic approximating the measured characteristic of Greitzer (1976a) is found to result in conclusions that compare well with observation. Thus, the paper gives a convenient and simple explanation of the boundary between surge and rotating stall behaviors, without the use of more intricate models and analyses including nonaxisymmetric flow dynamics.

No abstract

AC electrified railway systems show power quality problems such as harmonic current pollution, feeder voltage perturbation, and reactive power demand. These power quality problems have a bad effect on the AC railway system itself as well as other electric systems connected together. This paper investigates comparatively two configurations of a shunt active power filter (SAPF) for improving power quality in the AC railway systems. Different control algorithms corresponding to the installation position of the active power filter at the substation or at the sectioning post are proposed respectively. A comparative case study on the two positions of SAPF has been performed comprehensively.

No abstract