Flow-induced vibration analysis of a prototype pump-turbine runner during turbine start-stop transient process

Abstract

Recently more start-stops per day of the pump-turbine units are required by the power grid for load regulation. During the turbine start-up and shut-down transient processes, the flow and pressure of the prototype pump-turbine change dramatically at different guide vane opening angles. The extremely unsteady pressure fluctuation in the flow passages can induce large deformation, stress concentration, and strong vibration of the pump-turbine runner. Therefore, it is significantly important to study the unsteady flow characteristics and the corresponding flow-Induced vibration of the runner during turbine start-up and shut-down transient process. In this investigation, a 3D model of the pump-turbine unit including the flow passages of the spiral casing, stay vane, guide vane, runner, and draft tube, crown chamber, band chamber, labyrinth seals, and balance pipes are constructed. The flow characteristics of the unit during the turbine start-up and shut-down process were analysed by coupling the 1D pipeline calculation and 3D turbine flow domain calculation. By mapping the pressure distribution of the fluid domain to the runner structure domain, the flow-induced dynamic behavior of the pump-turbine runner is performed, and the large deformation and stress concentration of the runner are investigated in detail. The flow-induced vibration results achieved are able to provide meaningful suggestions for safe operation and for improving the pump-turbine runner design.

Numerical Investigation of Flow and Structural Characteristics of a Large High-Head Prototype Pump–Turbine during Turbine Start-Up

“…[21,22]. Researchers have further confirmed the reliability of the numerical investigation according to the field measurement data for the turbine start-up of the pump-turbine units [23,24]. The results show that under the condition of limited computational resources, selecting key time points for static calculations is an efficient means to analyze the flow characteristics of the unit during the transient process.…”

FSI simulation of a high-head pump-turbine during load rejection process

“…He [12][13][14] et al took the clearance flow into the fluid calculation and successfully simulated the resonance curves of the runner start-up process. Zhou [15] et al studied the stress characteristics of the runner during the start-stop process, and found that the location of the maximum stress is transferred at different stages of the start-stop process. Biner [16,17] studied the stress and damage of a variable speed pump-turbine during start-up, and pointed out that the total damage can be reduced by 7.7 times if applying the variable speed best efficiency point (BEP) tracking strategy.…”