Research On Feeding Device Design And Coupling Technology Of Straw Fiber Preparation Machine System For Straw Fiber-based Mulching Film Preparation

Straw fiber-based mulching film is a completely biodegradable film made from crop straw,which has the functions of temperature regulation,moisture conservation,weed inhibition and soil fertility enriching.D200 straw fiber preparation extruder can process the crop straw into the fiber material needed for preparation of film using extrusion explosion method.Extrusion explosion is a physical pretreatment method which has advantages such as low cost,simple operation,continuous work and environmental protection.However,due to special physical properties such as easy winding,high adhesion and poor fluidity of crop straw,the phenomenon of bridging and blocking often occurs when the moderately finely treated straw is fed into the feeding entrance of fiber preparation extruder.In order to guarantee continuous and stable operation of the extruder,it is necessary to design a feeding device to solve above problems.This research aimed at fiber preparation extruder,a semi-open turning diversion screw forced transporting and feeding device was designed,and parameters optimization experiments of feeding device performance and coupling operation between feeding device and fiber preparation extruder were carried out.The main research contents and conclusions were as follows:(1)Research on straw related physical property parameters determinationTwo kinds of crop straw(rice straw and corn straw)were chosen as research objects,straw diameter was determined.The change law of straw moisture content when soaking time increased was explored,and the nonlinear equation between straw moisture content and soaking time was established.Straw tap bulk density was determined using vibration shock method.Double-factor experimental design method was applied to determine straw sliding friction coefficient at different levels of moisture content and normal pressure.The determination of straw related physical property parameters can provide data reference for subsequent design and optimization of structural and working parameters of feeding device.(2)Research on key components design of straw raw material feeding deviceRice straw was chosen as research object and whose related physical properties were referenced,a semi-open screw transporting and turning diversion feeding device was designed based on screw transporting theory.The mechanical and kinematics models of screw transporting were established respectively,and main structural parameters of device were determined:screw outer diameter 250 mm,pitch 250 mm,core shaft outer diameter 51 mm and wall thickness 10 mm,radial clearance between screw outer edge and U-groove inner wall 9 mm.The adjustable surface turning diversion plate was designed by establishing the turning diversion model.(3)Research on parameters optimization of feeding deviceIn order to obtain the optimal working and structural parameters combination of feeding device,rice straw was chosen as research object.Four factors and five levels quadratic regression orthogonal rotation center combination experiment method was applied to carry out optimization experiment with straw length,straw moisture content,core shaft rotation speed and diversion angle as experiment factors,and discharge rate and variation coefficient of discharge rate as experiment indexes.The results showed that the optimal parameters combination was as follows:straw length 100 mm,straw moisture content56%～83%,core shaft rotation speed 75～96 r/min,diversion angle 36°.In this condition,discharge rate was 16.70～18.14 kg/min,and variation coefficient of discharge rate was 3.75%～10.00%.The verification experiment results were within the optimization range,meeting requirements of straw feeding.(4)Research on parameters optimization of coupling operation between feeding device and fiber preparation extruderIn order to obtain the optimized parameters combination of coupling operation between feeding device and fiber preparation extruder,rice straw was chosen as research object.Four factors and four levels orthogonal experiment method was applied to carry out parameters combination optimization experiment with straw moisture content,core shaft rotation speed,spindle rotation speed and die clearance as experiment factors,and fiber yield and tensile index as experiment indexes.The results showed that the optimized combination was as follows:straw moisture content 75%,core shaft rotation speed 85 r/min,spindle rotation speed 90 r/min,and die clearance 4 mm.In this condition,the verification experiment was carried out and results showed that relative error between the experimental value and the predicted value was less than 2%,indicating the results were true and reliable.Fiber yield was more than 85%,and tensile index was more than 15 Ng/m~3,meeting requirement of fiber preparation and film strength.The operation stability verification experiment results showed that variation coefficient of fiber productivity was less than 13%,which proved that coupling system between feeding device and fiber preparation extruder operated stably.The feeding device and fiber preparation extruder designed in this study can work in a coordinated and stable way.