Investigation of the Starting-Up Axial Hydraulic Force and Structure Characteristics of Pump Turbine in Pump Mode

Abstract

During the starting up of the pump mode in pump turbines, the axial hydraulic force acting on the runner would develop with the guide vane opening. It causes deformation and stress on the support bracket, main shaft and runner, which influence the operation security. In this case, the axial hydraulic force of the pump turbine is studied during the starting up of pump mode. Its influences on the support bracket and main shaft are investigated in detail. Based on the prediction results of axial hydraulic force, the starting-up process can be divided into “unsteady region” and “Q flat region” with obviously different features. The mechanism is also discussed by analyzing pressure distributions and streamlines. The deformation of the support bracket and main shaft are found to have a relationship with the resultant force on the crown and band. A deflection is found on the deformation of the runner with the nodal diameter as the midline in the later stages of the starting-up process. The reason is discussed according to pressure distributions. The stress concentration of the support bracket is found on the connection between thrust seating and support plates. The stress of the runner is mainly on the connection between the crown and the blade’s leading-edge. This work will provide more useful information and strong references for similar cases. It will also help in the design of pump turbine units with more stabilized systems for reducing over-loaded hydraulic force, and in the solving of problems related to structural characteristics.

Research on the Flow-Induced Stress Characteristics of Head-Cover Bolts of a Pump-Turbine during Turbine Start-Up

“…Since the model tests and prototype tests of large hydraulic turbines are usually very expensive and time-consuming, scientific numerical simulation becomes an alternative method to investigate the fluid dynamics and the structural dynamics of the turbine units. Many researchers [25][26][27][28][29][30][31][32][33] have verified the reliability of numerical calculations of hydraulic turbines by comparing the calculated results with the measured ones. Several studies [34][35][36] have used the dynamic mesh technique to simulate the unsteady flow of PT units in transient processes, and the simulation results were in good agreement with the experimental ones.…”

“…However, a transient process calculation took months even with many computational resources, which could not provide fast feedback to the PT designers of real engineering projects within a given time frame. For this reason, some scholars [26,27,[37][38][39] have proposed a simplified method to calculate the fluid flow at each critical moment of transient processes and to study the flow-induced stresses of PT structures. This calculation method requires substantially less time and computational resources, and the simulation results agree well with corresponding measured ones.…”

“…The k-ω model is used to simulate the flow near the wall, while the k-ε model is used for the flow away from the wall. It gives highly accurate predictions of the onset and the amount of flow separation under adverse pressure gradients [26,27,44]. The spiral case, stay vane, guide vane, pressure-balance The SST k-ω turbulence model, which effectively blends the k-ω and k-ε models, was used to perform the fluid dynamic calculations.…”

Analysis of Internal Flow Characteristics of a Startup Pump Turbine at the Lowest Head under No-Load Conditions

“…Meanwhile, the pump turbine is installed vertically, and the changing characteristics of the axial water thrust directly affect the safe and stable operation of the unit. Excessive axial water thrust causes accidents such as unit lifting and tile burning [20,21]. Runner gap and pressure-balance pipe are important factors that affect the axial water thrust of the unit.…”

Effect of the Diameter of Pressure-Balance Pipe on Axial Hydraulic Thrust

“…As far as the research is concerned, the larger the selection range of different load values is, the more intensive it is; the data in this paper comes from the test of 100%, 75% and 50% load turbine conditions provided by the power station, and the specific conditions are shown in Table 3. The research and calculation methods of the axial force in this research group are very mature, and the relevant accuracy can be referred to in the published article [14]. The comparison results of the unit parameters calculated under each working condition and the interpolation of the unit parameters according to the model test are shown in Table 4.…”