Unsteady flow and fluid-structure interactions in turbines with full- and partial admission

由于可再生能源的使用越来越多，对汽轮机的灵活性和部分负荷运行提出了更高的要求。使用控制级，可以实现蒸汽涡轮机的有效部分负载操作。在控制级的部分负荷进气期间，在进气和不进气部分之间出现高速度和压力梯度，这是造成不稳定流动条件和转子叶片的强循环应力的原因。这些复杂的流体和结构力学现象的实验研究非常有限，可以在公开文献中找到。部分进气涡轮的数值研究是提高对这些现象的物理理解的适当工具。然而，验证的数值代码使用实验是必要的，但限制由于不良的实验数据库。 在这个项目中，将在大型轴流空气涡轮机中进行详细的实验研究。计划将联合收割机的流动研究与激光光学测量系统、流道内和侧壁处的时间分辨测量以及转子叶片上的非定常型面压力测量相结合。基于这些详细的流量测量，将以高的时间和空间分辨率描述流量状况。首次通过组合实验捕捉部分进气对控制级来流场的影响、与叶片通道内流场的相互作用以及叶片的时间分辨结构-机械激励。此外，还将使用商用RANS求解器进行瞬态三维CFD模拟，并通过实验进行验证。数值结果将获得深入了解流动的细节，这不能捕捉到的实验或太多的努力，分别。此外，计划补充参数变化，以提高物理理解，并检查其他机器的应用结果。通过耦合的流体-机械/结构-机械研究，将研究部分进汽引起的转子叶片的激励。这些研究的目的是提高对汽轮机中部分进汽引起的三维时间分辨流动现象以及流体-结构相互作用的物理理解。未来，该项目的结果将有助于改进汽轮机的设计过程，以提高运行灵活性和部分负荷运行的效率，这是下一代汽轮机所必需的。

Due to the increasing use of renewable energy sources, higher demands on the flexibility and part-load operation of steam turbines arise. Using a control stage, an efficient part-load operation of steam turbines can be realised. During part-load admission of the control stage, high velocity and pressure gradients between admitted and not admitted sections appear, which are responsible for unsteady flow conditions and a strong cyclic stress of the rotor blades. Very limited experimental investigations of these complex fluid- and structure-mechanical phenomena can be found in open literature. Numerical investigations of partial-admitted turbines are an appropriate tool for improving the physical understanding of these phenomena. However, a validation of the numerical codes using experiments is necessary, but restricted due the poor experimental data base available. In this project detailed experimental investigations in a large-scale axial air turbine will be performed. It is planned to combine flow investigations with a laser-optical measurement system, time-resolved measurements within the flow channel and at the sidewalls as well as measurements of the unsteady profile pressures on the rotor blades. Based on these detailed flow measurements the flow conditions will be described with high temporal and spatial resolution. For the first time, the influence of partial admission on the incoming flow field of the control stage, the interaction with the flow field within the blade passages as well as the time-resolved structure-mechanical excitation of the blades can be captured with combined experiment.In addition, transient 3D CFD-simulation using a commercial RANS-solver will be carried out and validated with the experiments. The numerical results will gain insight into flow details, which cannot be captured by the experiments or with too much effort, respectively. Further on, supplementary parameter variations are planned in order to improve the physical understanding and to check the application of the findings to other machines. By coupled fluid-mechanical / structural-mechanical investigations the excitation of the rotor blades due to the partial admission will be investigated.Aim of these investigations is to improve the physical understanding of the 3D time-resolved flow phenomena as well as fluid-structural interactions due to partial admission in steam turbines. In future, the results of this project will contribute to an improved design process of steam turbines for higher operational flexibility and improved efficiency for part-load operation, necessary for forthcoming generations of these turbomachines.