Study On Slurry Flow Mechanism And Structure Design Of Slurry Flow Channel Of Dilution Water Hydraulic Headbox

Tissue paper is a fast-moving consumer goods that is closely related to the lives of ordinary people and promotes the development of the national economy,and with the improvement of people's demands about the quality of tissue paper,the tissue paper machine has been renewed and upgraded.As a high technical device,the headbox play an extremely crucial role in the paper machine and has a great influence on the quality of sheet forming.Based on the production of a toilet paper,this paper designs the slurry flow channel structure of the hydraulic headbox,and study deeply the mechanism of each functional component by the computational fluid dynamics method which provide a scientific and reliable reference basis.The structural design of the slurry flow channel of the headbox should take account of various factors,which not only related to the quantitative,width and performance of the paper produced,but also related to the concentration and type of the pulp and the speed of the paper machine.The computational fluid dynamics method was utilized to simulate the slurry performance of the circular and conical sections of the tapered header.In terms of the uniformity of outlet velocity distribution,the uniformity of fiber concentration distribution,and the uniformity of outlet flow of each branch,the simulation outcome illustrates that the uniform slurry performance of the conical sections of the tapered header is higher than that of the circular section of the tapered header.On the basis of the original round pipe dilution water adding device,a ring dilution water adding device was invented,and the mixed flow state of the slurry and the dilution water in the two devices was numerically simulated.In terms of the mix content of the dilution water and the slurry,the uniform content of velocity distribution as well as the length required for the mixing are completed absolutely.the simulation consequent demonstrates that the function of the ring dilution water adding device is superior to that of the round pipe dilution water adding device.The cross-sectional area of the step diffuser will contribute to the diversification on the flow state of the slurry and this effect was investigated.The simulation results indicate that under the premise that the diameter of the tube bundle inlet is constant,when the diameter of the outlet tube bundle become larger,the turbulent kinetic energy will turn into more intense and the velocity distribution of the outlet plane transform more uniform.However,the distribution of fiber concentration is more uneven.Investigating the principle of submerged jet in the steady flow chamber,it is found that the adjacent jets injected from the respective tubes will interaction and attract each other.As the length increases,the difference of speed and pressure gradually become smaller,the slurry flow gradually become more uniform,and after sufficient development,a uniform outlet plane is finally formed on the steady flow chamber.Investigate the influence of the nozzle structure on the spray angle and jet velocity of the net slurry flow.The simulation results reveal that the spray angle will decrease with the increase of the ratio of the horizontal projection length of the lower lip and the opening ratio of the lip opening height X/h;the spray angle will decrease with the increase of the ratio of the vertical projection length of the metal plate to the lip opening height Y/h.As the inclination angle of the upper and lower lips increases,the spray angle increases to the highest point and then continues to fall.