Abstract
The startup process occurs frequently for pumped storage units. During this process, the rotating rate that changes rapidly and unsteady flow in runner cause the complex dynamic response of runner, sometimes even resonance. The sharp rise of stress and the large-amplitude dynamic stresses of runner will greatly shorten the fatigue life. Thus, the study of start-up process in turbine mode is critical to the safety operation. This paper introduced a method of coupling one dimensional (1D) pipeline calculation and three-dimensional computational dynamics (3D CFD) simulation to analyze transient unsteady flow in units and to obtain more accurate and reliable dynamic stresses results during start up process. According to the results, stress of the ring near fixed support increased quickly as rotating rate rose and became larger than at fillets of leading edge and band in the later stages of start-up. In addition, it was found that dynamic response can be caused by rotor stator interaction (RSI), but also could even be generated by the severe pressure fluctuation in clearance, which can also be a leading factor of dynamic stresses. This study will facilitate further estimation of dynamic stresses in complex flow and changing rotating rate cases, as well as fatigue analysis of runner during transient operation.
Highlights
Pumped storage units have great significance to the power grid
Pumped storage units are required to absorb extra electric energy generated by wind or sun, maintaining the safety and stability of power grid
As the critical component of pumped storage unit, the pump turbine runner may suffer from dynamic stresses, and sometimes cracks at the location of stress concentration
Summary
Pumped storage units have great significance to the power grid. Recent years have witnessed the development of new renewable energy sources such as wind and solar. Both wind and solar are not stable and continuous, causing large oscillation for the load of electrical power grid. Pumped storage units are required to absorb extra electric energy generated by wind or sun, maintaining the safety and stability of power grid. Pumped storage units can help solving the problem of frequency modulation, phase modulation as well as peak regulation for their effective storage and flexible switch between turbine mode and pump mode [1]. As the critical component of pumped storage unit, the pump turbine runner may suffer from dynamic stresses, and sometimes cracks at the location of stress concentration. Damages have been reported by many researchers [2,3,4] and may cause a great loss to power station
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