Influence of a circular strainer on unsteady flow behavior in steam turbine control valves

Abstract The influence of a circular strainer on unsteady flow behavior in steam turbine control valves, which are commonly placed between an intermediate-pressure turbine and a boiler in thermal power plants, was numerically studied. A porous-medium model, which established the dependencies of the pressure drop through the strainer on the magnitude and direction of the fluid flow’s velocity, was validated by experimental measurements in a water flow test rig. As the benchmark configuration, a valve without a strainer was used for comparison. The turbulent steam flow in the complex serpentine channel was simulated with the implementation of the proposed porous model for the strainer. The numerical results demonstrated that placing the strainer in the main valve resulted in dramatic changes of the flow patterns in the main valve’s chamber and its diffuser, and even in the downstream throttle valve. The complex steam flow in the main valve was efficiently managed by the circular strainer, significantly reducing the cross-sectional force on the main valve’s spindle; this is attributed to attenuated oscillation of the annular flow around the main valve’s seat. As for the downstream throttle valve, the pressure drop and the fluctuating lateral force on the spindle were intensified, which was shown to be closely related to the continuous impingement of the flow onto the throttle valve’s cavity wall. In comparison with the configuration without a strainer, the placement of the strainer in the main valve gave rise to a pair of intensified secondary vortices in the diffuser section behind the throttle valve.