Numerical Modeling of Flow-Induced Instabilities in a Cage-Type Steam Turbine Control Valve

Flow-induced vibration is a low-frequency failure phenomenon caused by the interaction between fluid flow and physical structure. This work aims to investigate the potential of flow-induced instability within a cage-type steam turbine control valve in which the throttle valve stem failed due to flow-induced vibration. In this work, a computational fluid dynamic (CFD) analysis was carried out based on a 3-dimensional, unsteady, finite volume method that solves Reynold-Averaging Navier Stokes at the cell-centred and Realizable k-ε as the turbulent modelling. In the present work, the double-seated throttle valve was utilized to regulate steam flow with a capacity of 10 kg/s, a rated pressure of 44 bar, and a temperature of 410 °C entering the control valve system from a vertical inlet to the horizontal outlet into the turbine. Based on the CFD analysis performed, it was found that the CFD predicted the existence of significant vortex-shedding activities due to strong aerodynamic interaction between the cage and the throttle valve component. The dominant broadband frequency determined by the unsteady calculation closely matches the frequency measured through the field measurement.