Active Flow Control of Hydrodynamic Instabilities in Francis Turbines based on Linear Stability Theory

基于线性稳定性理论的混流式水轮机水动力不稳定性主动流量控制

• 批准号: 429772199
• 负责人: Professor Dr.-Ing. Kilian Oberleithner
• 金额: --
• 依托单位: Institute of Thermophysics
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/429772199?language=en
• 关键词: Active; Flow; Control; Hydrodynamic; Instabilities

To guarantee a stable electricity grid in the future, flexible energy sources are needed to balance the intermittent contribution from weather-dependent renewables such as solar or wind power. Hydropower plants are a well suited energy source for balancing intermittent energy contributions due to their flexible operation capabilities. Most hydropower plants are running Francis turbines, which need to be operated at part load to provide the required energy balance. Under these operating conditions a strong swirling flow is generated in the draft tube that gives rise to a helical vortex structure known as the precessing vortex core (PVC). Recent developments in linear stability theory allow to identify this structure as a globally unstable mode that is triggered by a hydrodynamic feed-back process in the draft tube of the turbine. In this project we use global linear stability theory and related adjoint methods to develop flow control solutions that are tailored to this instability. Key goal is to develop a control solution that suppress the PVC with minimal energy input. The main innovation of this approach in comparison to previous control attempts is that the methodology is based on a rigorous theoretical framework that allows to derive an optimal flow control solution. This control will be validated first on a turbine mock-up using air as a working fluid and in the final state at a hydro turbine facility. The developed control methods range from open- to closed-loop periodic and constant forcing as well as shape modifications. The project is structured in a baseline study, controller development phase and an optimization phase. To characterize the flow dynamics at natural and controlled conditions, experimental measurements in air and water as well as numerical simulations are conducted in conjunction with novel empirical data reduction strategies. The project benefits from the strong background in linear stability theory and flow control of the group at the TU Berlin and the excellent experimental facilities and experience of the group at the Institute of Thermophysics within the field of Francis turbine flows.

为了保证未来稳定的电网，需要灵活的能源来平衡太阳能或风能等依赖天气的可再生能源的间歇性贡献。由于其灵活的运行能力，水力发电厂是平衡间歇性能量贡献的非常合适的能源。大多数水电站都运行弗朗西斯涡轮机，需要在部分负荷下运行以提供所需的能量平衡。在这些操作条件下，在尾水管中产生强烈的旋流，其产生被称为旋进涡核（PVC）的螺旋涡流结构。线性稳定性理论的最新发展允许将该结构识别为全局不稳定模式，其由涡轮机的尾水管中的流体动力反馈过程触发。在这个项目中，我们使用全局线性稳定性理论和相关的伴随方法来开发针对这种不稳定性的流量控制解决方案。关键目标是开发一种控制解决方案，以最小的能量输入抑制PVC。与以前的控制尝试相比，这种方法的主要创新在于，该方法基于严格的理论框架，该理论框架允许导出最佳流量控制解决方案。该控制将首先在使用空气作为工作流体的涡轮机模型上进行验证，并在水力涡轮机设施的最终状态下进行验证。开发的控制方法范围从开环到闭环周期性和恒定的强制以及形状修改。该项目分为基线研究、控制器开发阶段和优化阶段。为了表征在自然和受控条件下的流动动力学，在空气和水中的实验测量以及数值模拟结合新的经验数据减少策略进行。该项目得益于柏林工业大学在线性稳定性理论和流动控制方面的强大背景，以及热物理研究所在弗朗西斯涡轮机流动领域的优秀实验设施和经验。