A Procedure for Experimental and Numerical Investigations of Turbine Machinery Labyrinth Shroud Seals

Abstract

Labyrinth seals installed in turbine machines serve for decreasing the working fluid leakage through the clearances between the rotating and stationary structural elements in order to increase its flowrate through the flow path. The operational efficiency and reliability of all types of turbine machines (steam, gas, and hydraulic turbines; compressors; fans; pumps; etc.) depend to an essential extent on the type of seals (labyrinth, groove, etc.), which determine the working fluid leakage and intensity of hydrodynamic forces acting on the rotor. Therefore, those who design turbine machines should use a close-to-reality model of the flow pattern in labyrinth seals. Such a model was developed in the 1970s by A.G. Kostyuk with his coworkers at the Moscow Power Engineering Institute and is quite widely used in analyzing the dynamics of turbine machines. However, the procedures for thermal and aerodynamic design analyses of turbine machines, as well as relevant standards and handbooks, do not contain a description of this model nor do they contain recommendations for using it. At present, such a state of things becomes especially dangerous in connection with wide application of numerical methods of 3D design and analysis, when the use of an inadequately selected flow model (in particular, in seals) may give rise to essential errors. The article presents a review and scrutiny of the used numerical and experimental models of shroud seals; their drawbacks are shown, and a model adequately representing a real flow is described.