Numerical Simulation Of Hydraulic Characteristics Of Combined Deformation Parts Of Tee Pipe And Valve

Ball valve and T-tee combination deformation parts are now one of the most important combination forms of water pipe network connection,to control the flow rate,change the direction of water flow,saving pipeline materials have played a very important role,the pipeline connection and pipeline and valve combination deformation of water is extremely complex,accompanied by a variety of flow forms and energy loss.In order to study the characteristics of water flow movement and comprehensive local water head loss of the combined deformation parts of ball valve and T-tee pipe,and to provide certain reference for the loss of water flow energy of the water transmission network,this paper chooses the combined deformation parts of ball valve and T-tube,which are commonly used in the water transmission network,as the research object,and adopts the numerical simulation method.By setting different working conditions(velocity change,valve opening change,shunt ratio change,pipe diameter change,valve position change,etc.),the combined deformation parts are studied and analyzed,and the comprehensive local resistance coefficient changes in different working conditions and the size of its influencing factors are obtained,and the distribution and change of the flow field and streamline of the combined deformation parts under different working conditions are studied.Moreover,flow rate before and after the valve,valve core changes.The specific research content is mainly divided into the following aspects:(1)Taking the combined deformation parts of ball valve and T-shaped tee pipe as the research object,the combined deformation parts of DN63 equal diameter T-tee pipe and DN63×50 reduced diameter T-tee pipe and ball valve as PVC pipe,respectively,using Realizable turbulence model,Fluent software was used to conduct numerical simulation.The variation law and influence of the comprehensive local loss coefficient on the combined pipe fitting under different valve opening,Reynolds number and shunt ratio were analyzed.(2)By analyzing the flow field characteristics of the combined pipe fitting at different valve openings,the changes of velocity and streamline distribution are obtained.The results show that:The opening degree of ball valve has the most significant influence on the comprehensive loss of combination pipe fitting.With the increase of the opening degree of valve,the flow gradient in the spool decreases obviously,and the eddy current area before and after the valve also decreases obviously.When the opening degree of valve is greater than 70°,the loss coefficient gradually becomes stable.(3)The comprehensive local loss of composite pipe fitting is affected by Reynolds number.When the inlet Reynolds number is below 1.0×10~5,the comprehensive loss of composite pipe fitting is large.With the increase of the inlet Reynolds number,the loss coefficient gradually declines,and becomes stable when the Reynolds number is greater than1.8×10~5.The smaller the diameter of the pipe,the more intense the flow turbulence,the flow from the main pipe to the branch pipe has a strong bending flow,and the strong extrusion and change of velocity direction at the valve,resulting in a violent vortex,so the larger local head loss.(4)When the water flow is diverted from the main pipe to the horizontal side pipe and branch pipe,with the change of the shunt ratio,the change form of the water flow at the side pipe and branch pipe is different.The pipeline connecting the valve even appears backflow and vortex,and the curved flow in the two pipelines is different in size.When the shunt ratio varies from 0.4 to 0.6,the hydraulic characteristics of the combined deformation are similar,and the eddy currents generated have little influence on each other,so the local head loss coefficient changes little.In other shunt ratios,the velocity difference between the two pipes is large,and the turbulence and eddy current intensity generated at the combined deformation is large,so more losses are generated.Therefore,in the combination of ball valves and T-tees,the shunt ratio is controlled at 0.5 as far as possible.Through numerical simulation,the hydraulic characteristics of the three combined models under different influencing factors were analyzed,and the changing rules of velocity,streamline and comprehensive loss coefficient were obtained under different influencing factors.In the combination of ball valves and T-tees,the local resistance is generally at the junction of the main pipe and straight pipe and the upstream and downstream of the valve and in the spool,the shear action caused by water bending and the severe vortex at the combined deformation,the size of the velocity gradient are the causes of local loss.