This work presents an optimization study for designing a shrouded turbine diffuser. The goal of the study was to obtain the geometry of the hydrofoil shaped diffuser which maximizes the hydraulic power of a turbine with a given set of constraints. The optimization process has been based on an automatic cycle of geometry modification, meshing and CFD analysis of the flow field, including a loaded diffuser (actuator disk). Bezier curves were implemented to describe the diffuser section, which allowed exploring non pre-existent hydrodynamic shapes for the shroud, and the optimization process has been driven by the Simulated Annealing algorithm. The optimal diffuser was also simulated with various conditions of disk loading and considering different tip clearances between the disk and the shroud. The results have showed that the optimum diffuser achieves a power coefficient of approximately 118%. Also, this methodology provides the data to the rotor design process (flow rate and pressure drop), and can be used as a first step to define the preliminary characteristics of the whole equipment based on an optimized pre-design. Considerations about the optimal actuator disk loading for a shrouded turbine considering viscous effects and turbulence, tip clearance effects and rotor design guidelines are also discussed.

这项工作提出了设计带罩涡轮扩散器的优化研究。该研究的目的是获得水翼形扩压器的几何形状，该几何形状可在给定的一组约束条件下最大化涡轮的水力。优化过程基于流场的几何修改，网格划分和CFD分析的自动循环，包括加载的扩散器（致动器盘）。实施贝塞尔曲线来描述扩压器截面，从而允许探索护罩的不存在的流体动力学形状，并且模拟退火算法驱动了优化过程。在不同的磁盘加载条件下，并考虑了磁盘与护罩之间的不同尖端间隙，还对最佳的扩散器进行了仿真。结果表明，最佳扩散器的功率系数约为118％。而且，这种方法为转子设计过程（流速和压降）提供了数据，并且可以用作基于优化的预设计定义整个设备的初步特性的第一步。还讨论了考虑粘性效应和湍流，叶尖间隙效应和转子设计准则的带罩涡轮机最佳致动器盘负载的考虑。