| In recent years,in order to meet the requirements of energy saving,environmental protection and power supply stability in production and life,the development speed of pumped storage power stations is gradually accelerating.As an important flow component,pump turbines have received more and more attention for their overall performance and local parameters.However,after the long-term development of turbines,the external characteristics such as overall machine efficiency and output power are no longer the focus of investigation.The stability of the unit and more detailed internal flow characteristics and adjustment of local parameters are the current research directions.The flow turbulent action of the turbine of the pump turbine is mainly due to the rotor and stator interface between the vaneless area between the guide vane and the runner,and the vortex-band vibration inside the draft-tube.These two main factors constitute the periodic pulsation in the flow channel.In addition,the computational resources required for the conventional flow simulation are large,so the method of changing the channel layout is considered to reduce the calculation time.Finally,in order to build a holistic understanding of the pulsation feature,the fluctuating distribution in the unsteady flow of all channels under one operating condition is emphatically analyzed.Based on the above research directions,the main contents of this paper are as follows:(1)The method of calculating the amplitude of variable sampling points is introduced to reduce the frequency leakage due to non-periodicity of the signal,thereby reducing the random error on the related frequency amplitude.The method was applied to the pulsation of the measuring point in the vaneless area under all working conditions,and the relationship between the amplitude-frequency characteristics,the opening degree and the unit speed was obtained.The pulsation analysis of the single-open draft tube was performed to extract the main frequency characteristics within the positioning range,and the failing of existing experimental datas in calculating the low frequency were analyzed.(2)In order to save computational resources,investigate the simulation strategies for different channel layouts with different openings such as 11 mm,13mm,21 mm,27mm,and 35 mm,and compare the corresponding frequency amplitudes to verify the type of TBR analysis' s feasibility.At the same time,the relevant pulsation characteristics of the traditional whole-channel flow settings and the unsteady calculation of the traditional periodic transient analysis under variable channel arrangement are also calculated for some conditions.(3)Perform a full-channel numerical simulation on a working condition of 13 mm opening and analyze the frequency amplitude distribution of the rotor and stator interaction's pulsation.Before the calculation,the measurement points on multiple monitoring surfaces are arranged in the pre-processing,and after calculation,the measurement data is derived to perform the frequency distribution of frequency amplitudes in several ways.All above will provide reference for experiments and calculations for future turbine's retrofit design and for more complex flow simulation. |
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