Pressure Pulsation And Vibration Testing And Numerical Calculation Analysis Of A Hydraulic Turbine In The Bladeless Zone

Hydraulic turbine pressure pulsation and hydraulic vibration is a very complex stability problem of hydropower station,which is also a common problem.Hydraulic turbine pressure pulsation and vibration will not only cause power oscillation of the unit,cracking of the runner blades,but also whistling sound,plant vibration and even unit damage,which will cause huge economic losses.In this paper,the hydraulic turbine pressure pulsation and vibration test and numerical calculation analysis are carried out for the abnormal pressure pulsation and vibration of Unit 4of a power station under the above conditions,and the research results provide a reference basis for safe operation of the power station and reasonable avoidance of abnormal operating conditions.The main work contents and research results are as follows.1.The cause of vibration is confirmed by on-site testing of the turbine as hydraulic vibration,which is related to water head.The abnormal working condition appeared at222.8MW load,110.19 m gross water head and 80.449% guide vane relative opening value.On the test day,no abnormal pressure pulsation appeared at 222.8MW load and 80.449%guide vane relative opening value,118.13 m gross water head,so it can be determined that the cause of abnormal working condition vibration is related to the only variable water head.2.By calculating the head loss of the pressure pipe,the working head under the abnormal working condition is obtained.The reason for the hydraulic vibration of this turbine operating under abnormal working condition is found through calculation: when the unit increases the guide vane opening process,the flow rate of the pressure pipe in the diversion system increases with the increase of the guide vane opening,the internal flow velocity of the pipe in the diversion system will increase,and the value of the head loss is proportional to the square of the velocity,which in turn makes the head loss of this abnormal working condition as high as 4m,and due to the reduction of the working head The working point of 222.8MW load,110.19 m gross head and 80.449% guide vane relative opening value falls outside the safe operating range of the operating comprehensive characteristic curve given by the turbine manufacturer.3.Through CFD(Computational Fluid Dynamics)software,a three-dimensional geometric model of the turbine overflow components is established,and a reasonable computational mesh division is made in the fluid domain,and a non-constant numerical calculation of the internal flow field of the turbine is carried out to further analyze the internal flow field of the turbine when the abnormal operating conditions occur.The hydraulic vibration occurs under the operating conditions of 222.8MW load,110.19 m gross head and80.449% relative opening of guide vane because the turbulence energy,velocity and pressure pulsation increase caused by the abnormal operating point is outside the safe operating range of the comprehensive operating characteristics curve provided by the manufacturer.4.The time domain diagram of the simulation results is FFT transformed to obtain the frequency domain diagram,and the accuracy of the numerical simulation is verified by comparing and analyzing the simulated and real values of the pressure pulsation and main frequency at the guide vane outlet.