Global stability analysis of an idealized compressor blade row. II. Multiple-blade interactions

Abstract

A direct-adjoint mean flow global stability investigation of self-excited instabilities in an idealized, two-dimensional compressor blade row at off-design conditions is carried out. In this second part of the paper, the single-passage analysis is extended to multiblade passages by exploiting the properties of block-circulant matrices and Bloch-wave theory. By using this method, analyses for a large number of blade passages become computationally tangible, and the modal and nonmodal single-passage analysis from the first part of the paper can be augmented by considering multiblade effects arising in larger systems. This work shows that multiblade passages introduce additional unstable 10- and five-periodic synchronization structures arising from a tuned optimal phase relationship that is supported by the larger system. Self-excited low-frequency structures, which cannot be represented within a single-passage computation, are also uncovered and analyzed.