Mixing in Axial Flow Compressors: Part II — Measurements in a Single Stage Compressor and a Duct

This paper follows directly from Part I which contains not only the description of the facilities and the results for the C106 four-stage compressor but also the background, list of nomenclature, acknowledgement and references. The discussion and conclusions for Part I and Part II are given here. The single stage compressor results show the significant effects of inlet guide vane (IGV) wakes on mixing across the stage in the so called ‘free stream’ region; in the casing region tip clearance flow is shown to play an important role in mixing. Explanations for these results are given. Investigations were also carried out in a two-dimensional rectangular duct flow to reveal the mixing mechanism in the corner region similar to those formed by blade surfaces and endwalls in a compressor. Turbulent diffusion has been found to be the dominant mechanism in spanwise mixing; anisotropic inhomogeneous turbulent diffusion is mainly responsible for the non-uniform mixing in the corner region. The larger spread of tracer gas in the tangential direction than in the radial direction is mainly caused by the wake dispersion and relative flow motions within the blade wakes as well as secondary flow contributions in the end-wall regions.