Flow-Induced Dynamic Behavior of Head-Cover Bolts in a Prototype Pump-Turbine during Load Rejection

Abstract

In order to ensure stable grid operatiFon and improve power quality, active or passive load rejection of pumped storage power stations (PSPS) inevitably occurs from time to time. The rapid closing of the guide vanes will cause drastic changes in pressure pulsations in the flow channel of the pump-turbine (PT) unit. The high-level pressure pulsations during load rejection transfer to the entire flow passage of the PT unit and generate strong vibrations on the head-cover and the connecting bolts. In this study, the 1D/3D joint simulation of the pipeline in a pumped storage power station and the turbine flow channels including the flow domains of the runner, crown chamber, band chamber, upper and lower labyrinths and pressure balance tubes is carried out first. Then, by applying the calculated pressure loads on the head-cover, stay vanes and bottom ring of the PT unit, the flow-induced dynamic behavior of the structures including the head-cover bolts is analyzed in detail. The results demonstrate that pressure loads on head-cover bolts change dramatically during the load rejection process. The flow-induced deformation of the inner head-cover during the load rejection is larger than that of other structures, and the flow-induced displacement and stress of different head-cover bolts are not uniform. The achieved conclusions in this study can be a useful reference for the design and operation of head-cover bolts for other PT units and high-head Francis turbine units.

Application of Multi-Dimensional Hill Chart in the Condition Monitoring and Cost Estimation of the Francis Turbine Unit

“…Therefore, when the hydraulic turbine is operating at partial load (generally 40% to 75% of the full load), the vortex band will oscillate significantly due to the complex vortex motion in the draft tube. The strong vortex zone will cause the formation and expansion of fatigue damage zones in the metal and welds of the unit parts, causing cracks or even damage, which shortens the maintenance cycle [17]. Loose connecting parts will not only cause the breakage of these fasteners themselves, but also aggravate the vibration of the connected parts, causing them to be damaged quickly; the pulsating pressure of the water flow in the draft tube can cause cracks in the draft tube wall [18][19][20].…”

Force Characteristics Analysis of Yixing Pump-Turbine Head Cover Bolts

“…With the rapid development and application of fluid structure coupling technology, the calculation method of flow induced stress in pump turbines(PT) has also achieved certain results [18][19][20][21][22]. Some literatures have analyzed the steady-state and partial transient process stresses of the head cover bolts of PT [23][24][25][26][27][28][29]. Based on existing research, this article obtains accurate water pressure distribution on the head cover bolts of the Yixing pump turbine by the 3D flow field calculation method firstly, and then further loads them on the overall structure of the connection between the head cover and the stay ring.…”