Analysis of the Unsteady Flow Field in a Steam Turbine Control Valve using Spectral Proper Orthogonal Decomposition

Abstract

A significant share of the conversion of thermal into electrical energy is realized by steam turbines. Formerly designed for continuous operation, today’s requirements include extended part load operation that can be accompanied by highly unstable flow conditions and vibrations within the control valve of the turbine. The prediction of the flow at part load conditions requires large computational efforts with advanced turbulence modeling in order to compute the flow at a reasonable accuracy. Due to the unsteadiness of the flow, the evaluation of the numerical results itself is a major challenge. The turbulent structures require statistical approaches, of which the use of Spectral Proper Orthogonal Decomposition (SPOD) has proven itself as a powerful method. Within this paper, the application of the method on a critical operating point with a temporal excitation of pressure oscillations observed in the experiments with dry air is presented. Using SPOD, the dominating flow phenomena were isolated and flow structures visualized.

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“…Advanced turbine heat transfer concepts also been dealt through experimental and numerical studies (Wambersie et al [10], Trompoukis et al [11]). Unsteadiness attracts much interest in various fundamental research aspects as documented by the work of Brandstetter et al [12] and Windemuth et al [13]. Radial turbomachinery research is also considered in several details (Schroeder et al [14], Wittmann et al [15], Liao et al [16]).…”