Calculation And Analysis Of Tail Vortex Of Pump As Turbine

The massive consumption of non-renewable energy has caused my country to face serious energy shortages and environmental pollution problems.How to use energy efficiently has become the focus of the world’s attention.In many industrial productions,a large amount of residual pressure liquid is generated.Usually,these liquids flow through the pressure reducin g valve and the multi-layer orifice plate,and are discharged after the pressure is reduced,causing energy waste.The hydraulic turbine can be used to recycle this part of the liquid residual pressure and convert it into mechanical energy,so as to achieve the long-term goal of energy reuse,energy saving and emission reduction.In industrial applications,it is found that hydraulic turbines often have problems such as low hydraulic efficiency and unstable operation caused by pressure pulsation,and the tail water vortex is closely related to the above problems.This paper takes IS80-50-250 centrifugal pump reversing hydraulic turbine as the research object to carry out numerical simulation,and studies the structural characteristics and motion law of the t ail water vortex under different working conditions of the hydraulic turbine and its effect on energy loss and machine operation stability.The impact caused by the study found:The calculation of constant constant value for this hydraulic turbine model sh ows that there is a tail water vortex at the outlet of the pump reversing hydraulic turbine impeller,and its structure is helical and axially propelled.The more it deviates from the optimal working condition,the more obvious the vortex structure is.The vortex is closely related to the flow and speed of the turbine.Generally speaking,the larger the flow,the smaller the speed,the more obvious the axisymmetric of the vortex,the higher the coincidence of the centerline of the vortex core with the axis of the draft tube,the rotation direction of the vortex is opposite to the direction of rotation of the impeller;the smaller the flow,the higher the speed.The less obvious the axial symmetry of the vortex distribution is,the more obvious the deviation between the centerline of the vortex core and the axis of the draft tube,the rotation direction of the vortex is the same as that of the impeller,the vortex breaks and merges along the flow direction,and the flow is more turbulent.The tail water vortex will cause the hydraulic loss inside the hydraulic turbine.As the flow rate increases,the hydraulic loss caused by the tail water vortex increases,and the energy loss of the draft tube reaches 15.6%;as the speed decreases,the tail water vortex causes The hydraulic loss increased,and the energy loss of the draft tube reached a maximum of 24.7%.The non-constant value of the hydraulic turbine model is calculated,and the results show that the smaller the flow,the more obvious the change of the tail wa ter vortex structure with time,the more easily the vortex is attenuated and broken,the pressure pulsation caused by it has no obvious law and the greater the pulsation amplitude Large(the maximum is about 0.1),its influence on the stability of the machine cannot be ignored.The larger the flow,the less obvious the structure of the wake vortex changes over time,and the structure is more stable.The pressure pulsation caused by the wake vortex changes periodically and the amplitude is smaller(the minimum is about 0.05).The greater the flow,the greater the strength of the vortex,and the greater the draft tube loss caused by the vortex;the smaller the flow,the smaller the strength of the vortex and the smaller the loss of the draft tube.In order to control the tail water vortex of the pump reverse hydraulic turbine,a"cross"type deflector was installed inside the draft tube in this paper.The study found that after adding the deflector,the energy loss in the draft tube is reduced,especially for large flows.It is obviously reduced at low speed(n=800r/min,qv=85m~3/h).The results obtained in this paper provide a certain reference for understanding the shape and law of the tail water vortex of the pump reverse hydraulic turbine,and the energy loss and unstable operation caused by it.