| The process of China's agricultural modernization and urbanization has made great progress and generally crop productivity is on the rise.As an important renewable resource,hundreds of tons of straw are directly burned or discarded every year,causing serious air pollution and waste of resources.This is contrary to the concept of green development in agriculture.The reason for this phenomenon can be summarized as the excessive amount of straw,the lack of spatial distribution and the difficulty of collection.D-200 crop straw fiber extruder is the fiber preparation equipment which is high-yield,non-polluting and low-energy.Therefore,this study selected wheat straw,one of the main food crops,as the research object.The study is experimented by a combined method of theoretical analysis,three-dimensional modeling and finite element analysis.The main contents and achievements are summarized as follows:(1)Taking the cutting wheat straw as the research object,the key technical parameters are provided for the device designing by detecting the granularity and the friction characteristics under certain compaction conditions.The three factors of exercise at five levels orthogonal design and the linear mixed models analysis were used to detect the coefficient of sliding friction and internal friction separately.The results of sliding friction test show that the positive pressure and moisture content have a significant effect on the sliding friction coefficient of stainless steel plates(P<0.01).The length of straw affected the sliding friction coefficient of stainless steel plate significantly(P<0.05),with the sliding friction coefficient ranging from 0.565 to 0.767.The length of straw and moisture content have a significant effect on the friction coefficient of rubber sheet(P<0.01),but the positive pressure have no significant effect on the friction coefficient of rubber sheet(P>0.05).with the sliding friction coefficient ranging from 0.661 to 0.791.(2)Propose the overall plan of the raw material supply system,and design the immersion,stirring device,screw feeding device and the pressure regulating device of the machine.The three-dimensional modeling method was used to design and process the immersion stirring device and the size and model of variable clearance mould head.With the finite element analysis method,the statics of the screw feeding device frame is analyzed,and the sixth-order mode of the feeding spiral is also analyzed.(3)Based on the theoretical analysis of wheat straw friction characteristics,main structure parameters were determined by establishing a mechanical model of straw transmission,and the inclined spiral feeding device was designed.Experimental investigations were carried out with the method of L16(45)orthogonal test to obtain the optimal parameter combination.Spiral angle,speed of screw shaft and moisture content of straw raw materials were selected as research factors,and transfer efficiency was chosen as the evaluating indicator.The results showed that spiral angle,rotating speed of screw shaft and moisture content of straw raw materials had very significant effect on transfer efficiency(P<0.01).The order of the influence extent on feeding efficiency of wheat straw raw materials is moisture content,spiral angle and speed of screw shaft.The optimal combination of parameters occurred with spiral angle is 40°,speed of screw shaft at 200 r/min,moisture content is 65% when maximum transfer efficiency per unit time was 1040.8 kg/h and variable coefficient was 0.09.Practice proves that it is able to meet the design requirement.(4)The wheat straw was soaked and immersed as the test material,and the self-made variable clearance mould head was used as the test equipment.Experimental investigations were carried out with the method of L16(45)orthogonal test to obtain the optimal parameter combination.Clearance of mould head,working temperature and the speed of preparation machine were selected as research factors,and the initial beating degree and fiber yield were chosen as the evaluating indicator.The results showed that clearance of mould head and the speed of preparation machine had very significant effect on initial beating degree(P<0.01).Working temperature had effect on initial beating degree(P<0.05).Clearance of mould head and the speed of preparation machine had very significant effect on fiber yield(P<0.01).Working temperature had effect on fiber yield(P<0.05).The optimal parameters combination with initial beating degree occurred with the clearance of mould head is 5mm,working temperature is 90 °C and the speed of preparation machine at 105 r/min.The optimal parameters combination with fiber yield occurred with the clearance of mould head is 5mm,working temperature is 90°C and the speed of preparation machine at 120 r/min.Because there are differences in the combination of parameters selected by the two indicators,the fuzzy comprehensive evaluation method is used to compare the indicators,and finally the selected working parameters combination is: the clearance of mould head is 5mm,the working temperature is 90°C,and the speed of preparation machine at 110 r/min.The initial beating degree of the fiber parameters after processing is 21.9 °SR,and the fiber yield is 82.7%. |
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