异速对辊式玉米秸秆粉碎还田装置设计与试验

Design and experiment of double rollers maize stalk chopping device with different rotation speeds

针对玉米秸秆量大、韧性强,导致还田后秸秆粉碎不均匀影响后续整地和播种等问题,该研究提出了一种异速对辊及动态双支撑形式的玉米秸秆粉碎还田方式,并研制了相应的玉米秸秆还田装置,主要由捡拾粉碎单元、对辊滑切支撑单元、支撑板和机壳等组成。在异速动态双支撑条件下,通过对作业过程中玉米秸秆动力学分析和秸秆漏捡面积分析,对捡拾粉碎刀和对辊滑切支撑刀进行设计,建立了影响秸秆粉碎合格率的数学模型。以捡拾粉碎刀转速、L型甩刀折弯角、L型甩刀刃口长度和滑切支撑刀滑切角为因素,秸秆粉碎合格率为试验指标进行Box-Behnken试验。田间试验结果表明:当滑切支撑刀滑切角45°、捡拾粉碎刀转速1 700 r/min、L型甩刀刃口长度45 mm和L型甩刀折弯角40°时,玉米秸秆粉碎合格率为92.58%,与预测值误差<5%,满足国家标准要求。该研究提出的秸秆粉碎还田方式和研制的秸秆粉碎装置为玉米秸秆粉碎还田机设计和优化提供新的方案和技术支撑。

A large amount of maize stalks are produced each year,due to the maize is serving as one of the main grain crop in China.Maize straw retention to the field after chopped is widely used in most disposal approaches.However,the currently used single shaft maize stalk chopping and retention machine can not meet the quality requirements of stalk chopping,such as too long maize stalk after chopping,and the low chopping pass rate of maize stalk,particularly when the amount of maize stalk was large,while the scarf skin of maize stalk was toughness.The shortcoming of maize stalk chopping directly determines the next seeding production,seed germination,and final crop yield.This paper aims to propose a novel chopping method,and thereby to design a double rollers type stalk chopping and retention device with different rotation speed and dynamic double support.The device mainly included the shell,supporting plate,suspension device,gearbox,transmission,chopping and collecting blade,shaft of chopping,collecting blade,blade shaft of slide-cutting supporting blade,and slide-cutting supporting blade.In operation,the chopping and collecting blade with anticlockwise rotation,firstly collected and chopped maize stalk in the field;then the maize stalk was chopped in dynamic support of side-cutting supporting blade with same rotation direction of chopping and collecting blade.A mechanical analysis of maize stalk was conducted under the effect of chopping and collecting blade,as well the slide-cutting supporting blade.The results showed that the rotation speed of chopping and collecting blade,and the slide-cutting angle of slide-cutting supporting blade were the main factors to affect the stalk chopping process.Furthermore,a motion analysis of chopping and collecting blade was carried out,including two L-type blades and a straight blade.The results revealed that the bend angle and length along the cutting-edge of L-type blade,and the rotation speed of chopping and collecting blade,were the main factors to affect the unpicking rate of maize stalk,and chopping pass rate,when the number of chopping and collecting blade and operation speed of device were fixed.In the slide-cutting supporting blade,the cutting-edge curvilinear equation was in the form of the logarithmic spiral equation.Moreover,the range of slide-cutting angle was 30°-60°,due to the slide-cutting angle can be more than frictional angle between maize stalk and slide-cutting supporting blade,according to slide-cutting principle.Importantly,the cutting edge of slide-cutting supporting blade with sawtooth was designed to increase the fraction of maize stalk and slide-cutting supporting blade.Prior to accurately coordinating between chopping and collecting blade,and side-cutting supporting blade,the rotating speed range of chopping and collecting blade was determined as 1 150-2 500 r/min,to ensure the high stalk chopping pass rate.The rotation speed of slide-cutting supporting blade was one half that of chopping and collecting blade,to guarantee the speed of backward spread of chopped maize stalk.Simultaneously,the chopping and collecting blade,and side-cutting supporting blade,both were double helix arrangement to reduce machinery vibration,while increase machinery life.One device was installed 20 chopping and collecting blades,and 40 slide-cutting supporting blades.A quadratic rotation orthogonal combination test was used in the field research,to obtain the optimal structure parameters,where the chopping pass rate of maize stalk was set as test index.Some test factors were selected,including the cutting-edge bend angle of L-type blade(20° ≤γ≤60°),and cutting-edge length of L-type blade(30 mm ≤k≤60 mm),rotation speed of chopping and collecting blade(1200 r/min≤nY≤2 000 r/min),and slide-cutting angle of slide-cutting supporting blade(30°≤τ≤60°).The Design-Expert 8.0.6 software was applied to analyze the double factors interaction on stalk chopping pass rate,thereby to obtain the regression model between test factors and index.The primary and secondary factors that affect the maize stalk chopping pass rate were the rotation speed of chopping and collecting blade,the length of cutting-edge bend angle,the cutting-edge length of L-type blade,and the slide-cutting angle.In multiple objective optimization,the optimum ranges can be achieved,including the cutting-edge bend angle of L-type blade(41°≤γ≤57.64°),the cutting-edge length of L-type blade(41.7 mm≤k≤51.71 mm),the rotation speed of chopping and collecting blade(1 657.37 r/min≤nY≤1 889.97 r/min),and slide-cutting angle of slide-cutting supporting blade(36.55° ≤τ≤49.08°).In the field test,the rotation speed of chopping and collecting blade,the length of cutting-edge bend angle,and cutting-edge length of L-type blade,and slide-cutting angle were set as 1700 r/min,40°,45 mm,and 45°,respectively.The field test results demonstrated that the maize stalk chopping pass rate was 92.58% under the optimal working parameters,while the error with the predictive value(93.96%) was less than 5%,indicating the reliable optimization of parameters.The finding can offer a sound reference to improve the chopping quality of maize stalk in the chopping and retention machine.