Research On Torque Characteristics Of Guide Vane In A Pump Turbine

With the booming development of the electric power industry,the large-scale and high-capacity hydropower,wind power and nuclear power units are established one after another.In order to meet the flexible and efficient use of power systems,pumped storage units emerged.As the core energy conversion component of pump storage units,pump turbine is required keep safe,stable and efficient operation.High standards and strict requirements are put forward for the design and operation of modern pump turbine.In recent years,it is of great significance to study the stability of pump turbines,because of the frequent occurrence in the unit due to guide vane misstrip and raising-turbine accident et.al.The force conditions of the guide vane in the flow field are studied based on the experiment and numerical simulation.The three aspects of the guide vane at the hydraulic turbine mode and the pump mode are made a deep going exploration,which include hydraulic torque of the guide vane,the distribution of internal flow field and relevancy between hydraulic torque fluctuation and pressure fluctuation.The main contents are as follows.1.Relying on the hydroelectric equipment test-bed of high head in a domestic research laboratory,hydraulic torque of guide vanes in turbine mode and pump mode are measured under different guide vane opening.The torque measured by a resistive strain gauge,and the energy characteristic of typical operating conditions are measured too.The energy characteristics and the hydraulic torque distribution of the guide vane under the hydraulic turbine mode and the pump mode are obtained.The hydraulic torque coefficient of the guide vane at turbine mode is linear distributions,while at pump mode presents the parabolic distribution.2.A guide vane is set as non-synchronous guide vane at the position of the common non-synchronous locations.And the hydraulic torque of the non-synchronous guide vanes under different opening is measured.The effect because of non-synchronous vanes to the hydraulic torque of adjacent synchronized vanes is studied too.From the point of view of hydraulic torque,the maximum opening of the non-synchronous guide vanes is obtained.The flow field of the distributor is made changed by the use of the pre-opened guide vane.Optimal maximum opening of the non-synchronous guide vanes is related to the opening of the synchronous guide vane,and the difference value of two opening should less than 16.4%.3.The three-dimensional model and mesh generation of the pump-turbine is built.The two-equation SST k-? model is used to simulate the flow field in the typical operating modes of the pump-turbine,because the acquisition of internal flow field involving the analysis of the unsteady flow.The corresponding relationship between the torque distribution of guide vane and the internal flow field is studied.A large number of vortices produce in the runner field under the small opening of synchronous guide vanes at the turbine mode.Come to the reason,the mainly one is the excess flow area is small under the small opening,fluid cannot be fully filled with the channel of runner,so the vortex structure origin from runner crown then move to downstream gradually.4.The periodic fluctuation is existed during the operation of the unit due to the flow of the runner area and the distributor area.The pressure monitoring based on point average and the hydraulic torque monitoring of the guide vane is set in the internal flow field during the unsteady numerical simulation.The time-domain and frequency-domain characteristics of the hydraulic torque fluctuation and pressure fluctuation are analyzed.It is found that the low frequency pulsation of large amplitude is existed under small opening,and the amplitude is the highest at the shaft frequency and the blade-passing frequency.