Unsteady flow and fluid-structure interactions in steam turbine control valves – measures for the stabilization of spherical control valves

随着可再生能源在整体电力供应中所占份额的稳步增长，传统发电厂的灵活运行变得越来越重要。在未来，蒸汽涡轮机将被期望提供平衡功率，这需要对涡轮机进行快速且鲁棒的调节。通常，短期负载变化可以使用控制阀来实现，对于控制阀而言，在部分负载条件下的延长时间可能是一个主要挑战。根据阀门的设计，节流条件下的非稳定流动条件可能导致流体-结构相互作用和严重振动，可能导致机械故障。除了更复杂的设计之外，球形阀作为一种特别有振动危险的几何形状仍然被安装在特别是较小的汽轮机中。为了确保安全可靠的部分负荷运行，对流动拓扑结构的良好了解以及对流动不稳定性的准确预测是必不可少的。为此，实验研究很重要，但蒸汽涡轮机调节阀的可用试验数据（尤其是弹性装置）很少。根据以前DFG项目的结果，将研究新的几何措施（整流、涡流和湍流产生），用于有针对性地操纵流场和抑制调节阀中的流动不稳定性。结果支持，一个更稳定的操作阀在部分负载的目的，也考虑到可能的升级现有valves.Different阀配置将进行实验研究的比例控制阀，捕捉不仅是时间分辨的压力场，但也动态的阀门。随着声激励的研究，它与流场的相互作用是另一个主要的兴趣。实验研究将伴随着瞬态三维CFD模拟，这将提供一个详细的了解空间流场后，其验证对测试数据。除了刚性阀门外，还将使用耦合流动和结构模拟评估弹性配置，以便更好地理解激励机制和所研究的几何变化的影响。对球形调节阀设计中不同的阀门改型和流体与声共振的声学相互作用进行分析，其目的是增加汽轮机的灵活性，同时在部分负载操作时提高效率和流动稳定性。

With a steady growth of the share of renewable energy in the overall power supply, a flexible operation of conventional power plants becomes increasingly important. In the future, steam turbines will be expected to provide balancing power, which requires a fast and robust regulation of the turbine. In general, short-term load changes can be realized using control valves, for which the extended time at part load conditions can represent a major challenge. Depending on the valve design, unsteady flow conditions at throttled conditions can result in fluid-structure interactions with severe vibrations, possibly leading to a mechanical failure. Besides more complex designs, the spherical valve as a particularly vibration endangered geometry is still installed especially in smaller steam turbines. To ensure a secure and reliable part load operation, good knowledge of the flow topologies as well as the accurate prediction of flow instabilities are therefore essential. For that purpose, experimental studies are important but available test data especially for an elastic setup is rare for steam turbine control valves.Based on the outcome of the previous DFG project, new geometric measures (flow-straightening, swirl- and turbulence generation) for a targeted manipulation of the flow field and suppression of flow instabilities in control valves will be investigated. Supported by the results, a more stable operation of valves at part load is intended, also considering possible upgrades for existing valves.Different valve configurations will be investigated experimentally on a scaled control valve, capturing not only the time-resolved pressure field but also the dynamics of the valve. With the examination of acoustic excitations, its interaction with the flow field is another major interest. The experimental studies will be accompanied by transient 3D CFD simulations, which will provide a detailed insight into the spatial flow field after its validation against test data. Besides the stiff valve, the elastic configuration will be assessed using coupled flow and structural simulations enabling a better understanding of the excitation mechanisms and the impact of the investigated geometric variations.In the medium-term, the analysis of different valve modifications and acoustic interactions of the flow with acoustic resonances for a spherical control valve design is intended to increase the flexibility of steam turbines and simultaneously improve efficiency and flow stability at part load operation.