Study On Effect Of Disc Gap And Tooth Inclination On Fiber Morphology By Numerical Simulation

As one of the three types of wood-based panel, with greater intensity, more symmetrical structure, smooth surface and good machining properties, medium density fiberboard (MDF) has become widely accepted by the furniture, interior decoration markets, construction and other industries. During fiber production process, fiber separation is the crucial step of hot mill process. The fiber morphology quality of the fiber separation completed, has a significant impact on the fiber properties. Fiber separation strength of refiner disc determines the size of the fiber morphology.Rational disc tooth profile design can achieve the appropriate intensity of fiber separation. Study disc gap, tooth inclination on the quality of the fiber morphology with experiment and numerical simulation, analysis the impact of disc gap, tooth inclination changes on fiber separation environment variables, and establish mathematical relationship of Special Edge Load (abbreviations SEL) and fiber size, they are help to improve the design level of disc and guide the fiber separation to new depths, and for fiberboard production enterprises to improve fiber quality has important practical applications.Based on the theory of refiner plate fiber separation mechanism, the paper compared the eight test disc tooth structure parameter data and the eight kinds of fiber sample size measurement data and Analyzed tooth structure parameters, including teeth length, space width, tooth inclination and circumferential teeth, on the fiber morphology of comprehensive effect. Compared two groups in the eight kinds of mill. In comparison group, in addition to tooth inclination differences, other parameters are equal or close. Analyze the inclination of the single variable change on the quality of the fiber morphology.Combining hydrodynamic theory and computational fluid dynamics software, by numerical simulation method to analyze the fiber separation process of the thermal mill. Reveals the speed, trajectory, and wall shear stress distribution of dynamic grinding, grinding gap, static pressure grinding three basins that these environmental parameters cannot be detected in the actual working conditions. And combined hydrodynamic theory, analyzed the above distribution individually. Summarize the distribution of the parameters in the flow field of the disc model. Provide a theoretical basis for subsequent establishing the contact between fiber morphology and disc gap and inclination.On the basis of the above simulation result, combined the numerical simulation with the single variable experimental method, changing the disc gap and the inclination parameters respectively for4times in the model. Observe the effect of the disc gap changing on pressure, velocity, wall shear stress field of gap watershed in the two simulation groups, and the effect of the inclination change on the entire fiber watershed fluid trajectory and speed size. The above variables have influence on the strength of fiber separation and fiber separation time. It can be initially identified disc gap, tooth inclination changes on the quality of the fiber morphology. Also verified that the conclusions in the previous section.Based on the eight kinds of experimental disc tooth structure parameters data, calculating for each disc SEL。Used the SEL data and the corresponding to eight kinds of fiber samples dimension measurement data for simple regression analysis, and verified that the SEL has a significant linear relationship to the quality of fiber morphology. During the calculation of SEL formula, the inclination has been contained. The inclination influences the SEL, that is to say, it also has effect on the fiber size. The conclusion has also been verified on numerical simulation chapter.Study on fiber separation process by fiber separation process can improving fiber separation theory and provide theoretical support for disc tooth structure mechanism, providing a new idea and method for optimizing the disc tooth structure, but also for doing a positive attempt to use hydrodynamic theory to optimize the disc tooth structure.