Research On Pressure Fluctuation Of A Pump Turbine Under Various Operation Conditions

At present, the electric power system of China is developing in the direction of large units and large power grids. In order to ensure the safe and economic operation of power grid, it must improve the ability of regulation of the entire power system. At the same time, the grid needs a substantial proportion of the energy storage device to improve the operating conditions of various types of power plants or improve the quality of their power supply. In this context, the pumped storage power station technology is widely used, which is the world’s most sophisticated large-scale energy storage technology. Now, China has become the fastest growing country for the pumped storage power station project. Pump turbine, which is the core equipment of pumped storage power station, is developing quickly in the direction of high head and large capacity. Its stability has long been concentrated by the researchers. Compared to the conventional pump and turbine, the pump turbine needs to balance the requirements between those two properties, so the stability problem of pump turbine is more prominent.In this paper, the pressure fluctuation of a high head pump turbine under various conditions was researched by numerical calculation and model test. The main work of this paper is shown as follows:(1) The three dimensional model for the pump turbine model machine was established. The unsteady numerical calculation for the pump turbine at various operating points was carried out. And the pressure fluctuation value was obtained. The calculation scheme was verified by comparing the calculation results and test results.(2) The monitoring points were set at the vaneless space and vane passages and the pressure fluctuation with different guide vane openings was studied. The study included the changing of pressure fluctuation in the circumferential direction of the vaneless space and the pressure fluctuation characteristics with different guide vane opening. Further, the unsteady inner flow field with different openings was revealed, including velocity, pressure and turbulence kinetic energy distribution. And the inner flow change with time was also shown. The pump turbine can be operated at pump mode and turbine mode, so the pressure fluctuation under pump mode was also researched, which was compared with the fluctuation under turbine mode.(3) In order to research the influence of the misaligned guide vanes on the pressure fluctuation characteristics, a synchronized guide vanes condition and a misaligned guide vanes condition were researched. The pressure fluctuation distribution and its propagation were compared between these two conditions. The emphasis was placed on the characteristic change at the pre-opening guide vane nearby area. And then, the evolutions of the flow over time under the misaligned guide vanes condition were researched.(4) In the conventional numerical calculation for the pump turbine pressure fluctuation, the calculation usually calculated the pump turbine itself. The piping system was not included. The boundary conditions of the three dimensional numerical calculation were set in advance and cannot be a true condition of its boundary. Therefore, this paper used one dimensional characteristic method for the calculation of pumped storage power station piping system, and embedded it in the three-dimensional calculation. The piping system calculation program was coded by C programming language, based on Fluent user defined function. Then the pressure fluctuation of the prototype machine with the consideration of pipeline was researched. The pressure fluctuation characteristics of the prototype machine and the model machine were compared.