| Fiberboard is widely used because of its excellent physical and mechanical properties,decorative performance and processability.Fiber separation is an important part of fiberboard production.The refining plate is the executive component of fiber separation,and its performance is related to the quality and cost of fiberboard products.The groove structure is one important factor affecting the fiber separation performance of refining plate and the quality of fiber.The main objective of this dissertation is groove structure,which affects the state of fiber motion significantly.This thesis studied the influence of groove structure on the flow characteristics of fiber and fiber separation performance of refining plate.It provides a theoretical basis for the design of a new refining plate with a twist surface groove structure.This paper expounds the current research status of refining theories at home and abroad,discusses the Specific Edge Load theory,Specific Surface Load theory,C-Factor theory and their application difference.The dissociation process of wood chip in different regions of the refining plate is analyzed,according to the mechanism of thermo-mechanical refining plate separating fiber,and lay a foundation for performance evaluation of the refining plate and the establishment of mathematical model of fiber motion along the groove.In this paper,a mathematical model for the movement of wood fiber along the groove was established by using the theory of fluid kinematics based on fiber material fluid motion characteristics in grinding zone.The model was solved by the Navier-Stokes equation and motion trajectory equation for the two-dimensional flow of wood fiber along the groove to obtain the two-dimensional motion law of fiber flow in the groove flow field.Analysis of the groove structure parameters,which influence the energy loss of fiber motion in the grooves,by the formula of energy loss of viscous fluid flow,provides the theoretical basis and optimization direction for optimization design of the groove structure.The 3D model of refining plate flow field was established,the mesh was generated and construction of flow field mesh model which height fitting to real flow field.Calculation and analysis of the pressure and velocity distribution law of the groove flow field and 3D motion trajectory of the fiber particle,makes the motion law of fiber fluid in the flow field of refining plate more perfect.Analysis of the effect of disc groove structure parameters on the fiber flow state,comparison of numerical simulation results of different disc groove flow field,puts forward the design idea of refining plate with a twist surface groove structure.The new refining plate was designed with a twist surface groove structure according to the numerical simulation of the flow characteristics of the refining plate.Fiber separation of wood raw materials in the same condition were tested by using the refining plate with a trapezoid groove structure and new refining plate,performance of the refining plate with a twist surface groove structure was comprehensively evaluated through theoretical and experimental analysis.Results show that the fiber separation performance of the new refining plate was better than the traditional one.The conclusions of the numerical simulation of flow field of refining plate and the reasonability of structure design of the new refining plate were verified experimentally.A new idea for improving the quality of fiber preparation and reducing the cost of production is provided in this paper,including theoretical support for the design of the refining plate with new groove structure.The results described here will help improve the domestic research level on tooth structure of the refining plate and promote the development of fiber preparation in the direction of high quality and low energy consumption,promoting technological innovation and scientific and technological progress in China's fiberboard manufacturing equipment industry. |
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