Increase of Efficiency of Turbine Setting Based on Study of Internal Flows

Abstract

Turbo efficiency largely depends on the internal overflows. Labyrinth seals are used as internal ones. To determine their flow characteristics a simplified calculation model of the opening with a sharp edge is used. It is supplemented with the experimental coefficients obtained under conditions which are significantly different from as-build. These ratios do not take into account the ring gap shape, flow vortexes on the inlet, eccentricity, shaft rotation, scale factor. When designing, simplification data do not allow using a labyrinth seal with a minimum leak value. The aim of this work is to upgrade knowledge about the workflow in the labyrinth seals using the modern methods of computational fluid dynamics (CFD), which are going to increase the efficiency of the internal labyrinth seals. At the same time, the numerical and experimental studies of the labyrinth seal element were carried. The research tasks are to establish the correctness of CFD methods application for studying the flows in the essentially narrow slits and obtaining the visualizations of the workflow under various geometric and regime parameters, to give practical recommendations on the design of such seals. Velocity fluctuations in the labyrinth seal are identified. They result from the uneven distribution of pressure along its length. The seal design with a variable pitch that allows reducing the leakage to 30% is proposed. Shaft rotation causes leakage reduction to 20%.