Structure and Kinematics of the Vortex System in Axial Turbomachines

This investigation models the kinematics of the vortex system of an encased axial turbomachine at part load and overload applying analytical methods. So far, the influence of the casing and the tip clearance on the kinematics was solved separately. The vortex system is composed of a hub, bound and tip vortices. For the nominal operating point φ ≈ φ(opt) and negligible induction, the tip vortices transform into a screw. For part load operation φ → 0, the tip vortices wind up to a vortex ring, i.e. the pitch of the screw vanishes. For overload operation φ → ∞, the vortex system of the turbomachine forms a horseshoe, i.e. the pitch of the screw becomes infinite. Both, hub and tip vortices, are semi-infinite, straight vortex filaments.