Contribution to the dynamic response of hydraulic turbomachinery components

Resumen

Fatigue cracks, caused by flow-induced vibration, appear on some prototype trash-racks and turbine runners in the hydropower plants. Broken trash-racks are not uncommon producing a lot of damage in the turbines, and many cases have been reported. In order to avoid fatigue damages on the hydraulic turbomachinery components, it is extremely important to investigate the dynamic responses of these components. The dynamic responses are very complicated because these structures are submerged and are connected to other structures. A systematic research to accomplish this purpose has been carried out. Before studying the complex structures, the scaled models were analyzed to validate the finite element method (FEM). Firstly, dynamic response analysis of a trash-rack (one grille) was carried out in air and still water by experiment and simulation to validate the numerical method. Then the dynamic responses of two typical types of prototype trash-racks in hydraulic power plants have been investigated experimentally and numerically. The influences of fluid, and attachment conditions on the dynamic response of trash-racks were studied in detail. Before studying the complex turbine runners, the dynamic responses of circular disks and disk-blades- disk (DBD) structures were estimated to determine the influences of the design parameters. Then a reduced scaled model pump-turbine runner has been adopted to carry out dynamic response analysis by experiment and simulation. Natural frequencies and mode shapes of the model runner were calculated both in air and in water. The influence of fluid added mass on the dynamic response of the scaled model runner was evaluated by considering the effect of fluid-structure coupling (FSC). Subsequently, with the same procedure, the dynamic response analysis of the prototype pump-turbine runner was performed experimentally and numerically in air and with water. The effect of the fluid added mass and the influences of rotor system, including generator, main shaft, bearings, and head-cover and bottom ring components on the dynamic response of the prototype runner have been discussed in detail. The dynamic response analysis of the head-cover component was also conducted considering the boundary constrain of the rotor system.