Research On Impeller Design Of Water Flow-Controlled Turbo Couplings

As the development trend of large capacity and long distance of scraper conveyor,Traditional torque limiting and variable speed fluid couplings have been unable to meet it's needs.At present,Water flow-controlled turbo couplings for the scraper firstly adopts a double-cavity structure to improve the torque transmission capability,and the machine's heavy-duty soft start,overload protection and load balancing during multi-motor drive can be effectively solved by the liquid-filling amount in chamber controlled by the electro-hydraulic system during the operation,and widely used in the coal production industry.Impeller cavity shape is one of the most important factors affecting the characteristic curve of hydrodynamic coupling.In order to further understand the relationship between the cavity type and the original characteristic of the coupling,and to provide reference and basis for the cavity design and impeller of the coupling,this paper adopted the fluid simulation technology and combined with the beam theory analysis method to analyze and compare the flow situation inside the coupling and the original characteristic curve under different parameters,and studied the influence of the cavity type parameters on the output characteristic of the coupling.The main research contents and conclusions are as follows:(1)comparison of two cavity types commonly used.By using computational fluid dynamics software(CFD)and combining with the theoretical model of beam flow,the flow field of two types of peach cavity and XL cavity commonly used in water flow-controlled turbo coupling were simulated.Through analysis and comparison of internal flow field distribution and the original characteristic curve of them,it was found that the pump wheel import and export's maximum speed of XL cavity is smaller in braking condition,output characteristic curve is more flat at low speed ratio,maximum speed is more measurement under the rated conditions,curve is much steeper under the high speed ratio,characteristic curve of XL is closer to the ideal original characteristic curve.At the same time,it is found that the relative motion velocity distribution law is different from the beam current theory hypothesis;with the increase of the speed ratio,the relative velocity distribution law of the pump wheel inlet and outlet under different working conditions is changed,according to which the accuracy of the beam flow theory can be improved.(2)Influence of runner width B on original characteristics.On the basis of XLcavity,the pump wheel and turbine flow channel width B was changed,analysis of the change of the flow field and the original features were analyzed,it is found that the increasing of pump and turbine flow width B can reduce the overload coefficient under braking condition,increases the torque coefficient of measurement under the rated conditions,but when it increases to a certain width,the increase of coefficient of measurement under the rated conditions is not obvious.(3)Influence of inlet and outlet curvature radius of pump and turbine.On the basis of the peach cavity,the outlet curvature radius of the pump wheel and the inlet curvature radius of the turbine are respectively changed under the condition that the effective diameter remains unchanged.The changes in the flow field and the original characteristics are analyzed.It is found that the torque coefficient at rated working conditions can be improved by reducing the outlet curvature radius of the pump wheel.The overload coefficient under braking condition can be reduced by reducing the radius of turbine inlet curvature without reducing the torque coefficient at rated working conditions.(4)Cavity design method.The rated operating efficiency is improved by cavity design and the maximum torque is limited by baffle design.(5)Research on speed regulation characteristics.Although the traditional closed system can change the rotating speed by adjusting the liquid charge in the cavity,it has some problems such as unreliable performance,high heating in the system and easy blockage of the solenoid valve.Based on XL type cavity,through combining the baffle and width decrease on the right side of the turbine runner,the ideal speed curve was was obtained.the suitable and new method of speed control for water flow-controlled turbo coupling,this method has a wide range of speed regulation,and the advantages of cool quickly can make the water flow-controlled turbo coupling with full filled for long-term and stable operation.(6)Impeller strength check and experimental study.Firstly,the model of the water flow-controlled turbo coupling was established by impeller P/roe.The ANSYS Workbench was used to simulate the flow field under the braking condition and then the FSI one-way coupling analysis was carried out.It was found that the stress of the pump wheel was mainly concentrated at the bottom of the blade.The stress of the turbine is concentrated at the top step of the turbine hub,and the maximum stress of the intermediate shell appears at the inner ring step.The calculation shows that the impeller strength is safe;through the bench test of the coupling,the load is loaded tothe rated load,and the impeller is verified.reliability.The test results show that the XL cavity type and rated speed ratio(efficiency)are higher than the peach cavity,which verifies the correctness of the research methods and conclusions.This paper deepens the understanding of the flow field and original characteristics of the fluid coupling.The research content and conclusions of this paper can provide reference and basis for the design of valve-controlled hydraulic coupling.