Computational Study of Kelvin-Helmholtz Instability Created by Interaction of the Mainstream Flow and the Seal Flow in Gas Turbines

Abstract

The present paper gives a contribution to a better understanding of the emergence of Kelvin-Helmholtz instabilities (KHI) in gas turbines. In an earlier paper of the authors, the occurrence of the KHI’s near the rim cavity of a 1.5 stage gas turbine has been examined by use of CFD methods. It is shown that the KHI’s occur, when the swirl component of the hot gas flow is very strong. Due to the fact, that a high swirl is produced by the guide vanes of the first stage, this matter concerns all common gas turbines. In order to get a basic theoretical background of the emergence of the KHI’s, 2D CFD investigations of the flow behind a splitter plate have been performed showing the development of KHI’s downstream of the splitter plate. To validate the numerical results a comparison to test rig data is used. This shows that the numerical method can simulate the characteristics of the KHI’s. Furthermore, a parameter study is conducted to extract parameters describing the appearance of KHI’s, the vortex periodicity and stability criteria. The main intention of this paper is to deliver “KHI parameters”, which are able to describe the development of the KHI in gas turbine rim cavities.

Experimental Investigation of the Effect of Purge Flow and Main Flow Interaction in a Low-Speed Turbine Cascade Passage

“…Therefore, the vortices in P0 should be induced by the interaction of the main flow and the purge flow. Rabs et al [ 31 ] identified the Kelvin–Helmholtz vortices near the rim cavity, which is caused by the shear of the main flow and purge flow. The vortices in P0 should be the result of the downstream propagation of the Kelvin–Helmholtz vortices, which can also be proved by the low uniform local vortex strength in these regions.…”