Analysis Of The External Flow Field Of The PVA Fibers Dispersion Machine’s Hammers And Its Dispersion Performance Test

With the continuous development of the application of fiber reinforced concrete,polyvinyl alcohol fiber with its high quality physical,chemical properties and low price had gradually been paid attention to.The research and application of PVA fiber reinforced concrete was also more and more.The study found that high strength and high modulus PVA fiber in the concrete can form a uniform disperse three-dimensional grid system,because the grid system could help the concrete absorb kinetic energy under impacted.However,PVA fiber packaging bagged out often into clusters of fascicular,it’s difficult to form an ideal grid system after mixing with the concrete,and will seriously affected the fiber concrete performance.Therefore,the dispersity of PVA Fiber had become the focus of research at home and abroad.On the basis of studying the physical,chemical properties and geometrical characteristics of PVA fiber,the paper analyzed the working principle of PVA fiber dispersion and the relationship of the fiber’s the momentum and energy conversion in the mixing chamber.Reducing the distance between cylinder wall and the hammers sheet,changing the shape of the tube wall,expanding the outer diameter of the rotor,increasing speed and number of the hammer could enhance the dispersion machine productivity and fiber dispersity.Besides,according to the dispersion machine motion state of the fluid in the mixing chamber,increasing the turbulence intensity of the flow field could also improve the fiber dispersity.The paper induced the idea of fluid finite element into the PVA fiber material,considering PVA fiber flow as the fluid medium in the simulation and operation,and established the finite element model of PVA fiber flow.According to the motion characteristics of the external flow field of the hammers,the out flow field model of the hammers of the dispersion machine was established in Fluent,and obtained the pressure,velocity and turbulence distribution in the flow field.The results showed that the area from the lower part of cylinder to the outlet should be designed arc shape to increase of the force of the fiber on the cylinder wall.In the light of the influence parameters of the mixing hammers in the fiber dispersion,the study compared the distribution turbulent kinetic energy out flow of hammers of three groups of different hammer spacing.The results indicated that the smaller the spacing of the hammer was,the more favorable the dispersion of the fiber was,confirming the ideal spacing of the hammers in this study.Compared the distribution turbulent kinetic energy between hammers of seven groups of different wheelbase.The turbulent kinetic energy of the external flow field of the hammers was strongest when two hammer wide margin contact,determining the ideal wheelbase of this study.The difference between the highest point and the lowest point of the hammers,analyzing the velocity difference curve,confirm the optimum rotating speed.Determining the structure and parameters of the tube on the basis of the structure parameters,paper establish the integral model of the dispersion machine.At last,through field test,using the method of sample extraction,dispersion performance test machine of PVA fiber,when the speed reaches 700r/min,meet the engineering requirements on the dispersion properties.