A TEST RIG CONCEPT TO STUDY FLUID STRUCTURE INTERACTIONS IN A STEAM TURBINE VALVE

摘要

The power output of steam turbines is controlled by steam turbine inlet valves. These valves have a large flow capacity and dissipate a huge amount of energy in throttled operation mode. The dissipation process generates strong pressure fluctuations and leads to high dynamic forces potentially causing valve vibrations. A brief survey of the literature dealing with valve vibrations reveals that vibrational problems and damages mostly occur in throttled operation when jets, shocks and shear layers are present. Previous investigations of the authors reveal a feedback mechanism between the dynamic flow field and the vibrating valve plug. Depending on the flow topologies either axial or lateral forces will dominate the force spectrum. In this paper the design of a test rig including a scaled model of a steam valve is described. As it is difficult to analyse lateral forces in conventional experiments the model is designed not only to study the flow conditions but also the lateral and axial movement of the valve plug. To investigate and model the dynamic characteristic of the valve the entire periphery including the mechanical drive, sealing etc. needs to be considered. To ensure that fluid-structure-interactions are correctly scaled, dimensionless numbers derived with the Buckingham Pi Theorem are used as design criteria. Positions of the transmitters are selected based on results of numerical simulations.