Weisong Zhao,Yongsheng Chen,Zhenwei Wang, Biao Ma,Baihe Han,Mingjiang Chen

(1.Nanjing Institute of Agricultural Mechanization，Ministry of Agriculture and Rural Affairs，Nanjing,210014，China;2.College of Mechanical and Electrical Engineering,Xinjiang Agricultural University,Urumqi,830052,China)

Abstract: In this study,considering the poor delivery uniformity,unstable feeding,and easy blockage during the delivery of crushed cornstalks,a straw conveying device was designed.A vibrating plate was combined with a shifting roller,the key structural parameters of which were determined via theoretical analysis.Based on the conveying efficiency and coefficient of variation,the primary factors of operational performance (poking roller speed,eccentric distance,and speed ratio)and the range of values for each factor were obtained via single-factor experiments using a discrete element simulation analysis software,EDEM.The optimal parameter combination was as follows:a poking roller speed of 30 r/min,an eccentric distance of 9 mm,and a speed ratio of 1.Five verification experiments were conducted using this combination.The experimental results indicated satisfactory performance of the conveying device for crushed cornstalk.The conveying efficiency was 37.09 m3/h,and the coefficient of variation was 13.77%.The experimental results were consistent with the simulation results,indicating that EDEM software optimization results are feasible and highly accurate.

Keywords: cornstalk;crashed;conveying

0 Introduction

The comprehensive utilization of straw is significant for promoting environmental protection,resource conservation,and sustainable development of the agricultural economy.In 2015,China’s total straw production reached 1.04 billion tons,with a comprehensive utilization rate of 80.1%.According to the requirements of the Chinese government,the comprehensive utilization rate of straw in the country is expected to exceed 85% by 2020[1].The comprehensive utilization of straw currently includes its use for energy,feed,base materials,raw materials,and fertilizers.Crushing and transportation of straw should be realized prior to its utilization.

European countries such as Denmark began to analyze straw conveying technology in the 1970s.Owing to the development of a comprehensive utilization technology for straw,straw conveying technologies have matured gradually;hence,the associated systems and equipment are widely used.The study of straw conveying technology in China commenced relatively late;however,it has undergone rapid development in recent years[2-3].Several studies on the transportation technology of straw harvested from fields have been conducted,focusing on loose grass and bale transportation[4-5].However,studies regarding the conveying technology of crushed straw in fields remain limited.The conveying methods of broken straw primarily include pneumatic,screw,belt,and scraper conveying.To solve problems associated with crushed corn straw conveying,researchers have analyzed a theoretical screw conveyor model and designed a screw conveying device and a screw-pneumatic coupling conveying device[6-9].To resolve uneven accumulation and inclusions during straw conveying,researchers have designed a four-phase crankshaft step device for conveying and conducted an analysis of impurity removal based on its mechanism[10].The effects of corn stalk moisture and length distribution on belt conveying performance havebeen analyzed[11].The crushed straw conveying technology in China is not robust;during resource utilization such as straw fertilizing and carbonization,appropriate straw crushing particle size,high conveying efficiency,and good uniformity are required.Straw must be crushed and conveyed efficiently and uniformly to facilitate carbonization and fertilizing.However,the problems of low conveying efficiency,easy clogging,and poor stability must be further resolved and improved[12].

Considering the gapin existing research regarding straw conveying technology,the low conveying efficiency and poor uniformity during pretreatment (such as straw carbonization)and resource utilization have not been resolved.In this study,experiments and simulation studies were performed to investigate the conveying characteristics of crushed cornstalks.A combination of vibrating plate and poking rollers was proposed to improve the conveying performance of crushed cornstalks.A crushed straw conveying device was designed and optimized,and the main structural parameters of the device were determined through theoretical analyses.The operating parameters of the device were optimized using EDEM,and a bench test to provide a reference for future investigations on crushed straw conveying technologies.

1 Materials and methods

1.1 Design of test bench and operating principle

A stalk crushing and conveying test bench was designed.The overall structure primarily comprises a crushing roller,a stalk cleaning roller,a vibrating plate,a poking roller,an eccentric vibration mechanism,a frame,a belt conveyor,and other components,as shown in Figure 1.

The operating principle of the stalk crushing and conveying test bench is illustrated in Figure 2.When the machine is operating,cornstalk is fed into the crushing roller from the feeding hopper and then crushed into 3 cm to 5 cm segments under the low-speed shearing action of a dual-roller.The crushed cornstalks fall into asurge bin under the action of the stalk cleaning roller.The stalk cleaning roller and crushing roller operate simultaneously to achieve material return and mixing.The crushed cornstalks are then continuously deposited on the vibrating plate in the surge bin.When the space between the vibrating plate and poking roller is relatively filled with the crushed cornstalk,the poking roller starts to rotate,evenly delivering the crushed cornstalks to the belt conveyor.Thus,a stable and continuous feeding function is achieved.

Fig.1 Schematic of stalk crushing and conveying test bench structure1.Poking roller 2.Frame 3.Motor assembly 4.Feeding hopper 5.Crushing roller 6.Stalk cleaning roller 7.Surge bin 8.Vibrating plate 9.Crank-connecting rod 10.Belt conveyor

Fig.2 Operating principle of stalk crushing and conveying test bench

This design of the surge bin overcomes the problem of disordered and uncontrolled aspect of the stalk after crushed.Under normal operating conditions,the deposition density of cornstalks in the outlet area of the surge bin is high,exhibiting a relatively full and saturated state.The vibrating plate swung from left to right to compress the crushed cornstalks.The speed of the poking roller controlled the output of the crushed cornstalks;this speed and that of the belt conveyor should be equal to ensure appropriate thickness of the material layer on the belt conveyor.A quantitative and uniform conveying of stalk materials was achieved through the coordinated operation of the aforementioned components.Based on the operating requirements of stalk crushing and delivery,the main technical parameter requirements of the test bench are summarized in Table 1.

Tab.1 Main technical parameters of the stalk crushing and conveying test bench

1.2 Key structure design

1.2.1 Vibrating plate design

After free-falling into the surge bin,the crushed cornstalks were easily over-headed,resulting in abnormal operating conditions such as blockage of the surge bin and unstable discharge.Therefore,a vibrating platethat could discretize the crushed stalkagain to obtain a more evenly blended material and effectively prevent overhead and outlet blockage when excessive cornstalks are deposited in the surge bin was designed.

A schematic of the vibrating plate movement mechanism is shown in Figure 3.The vibrating plate,labeled asDE,was composed of a No.45 steel plate with a smooth surface and was connected to the poking roller shaftOthrough a connecting rod,DC.Based on the height of the test bench and the length of the crushing roller,the height of the vibrating plate was designed to be 500 mm.To ensure that the cornstalks falling on the vibrating plate can slide down smoothly,the minimum angleαbetween the vibrating plate and the horizontal line should be greater than the friction angle between the cornstalks and the 45 steel plate.The maximum value ofαshould be less than 90°,andEOshould belonger than the sum of the radius of the poking roller and the eccentric distancee1.The lengths ofDE,EO,andDCshown in Figure 3 were 280 mm,150 mm,and 265 mm,respectively.The eccentric distancee1affects the amplitude of the vibrating plate.If the amplitude is extremely small,it will not prevent arching and overhead.In contrast,if the amplitude is extremely large,it will be directed against the crushed cornstalks,thereby scattering them.This is unfavorable for the shifting of the poking roller.Initially,e1was set to 5 mm.

Fig.3 Schematic of vibrating plate movement mechanism

1.2.2 Poking roller design

A poking roller was designed to output the crushed stalk in the surge bin uniformly,quantitatively,and continuously.As shown in Figure 4,the poking roller comprised a poking roller shaft,poking plate,and side flange,as well as five poking teeth evenly distributed around the inner shaft.The poking efficiency of the poking roller was affected by the length of the poking roller,diameters of the inner and outer shafts,and rotation speed.Based on the length of the crushing roller,the length of the poking roller (L)was determined to be 780 mm.To achieve the desired strength of the poking roller and to satisfy the requirements of poking efficiency,the inner diameter (d)and outer diameter (D)of the poking roller were preliminarily designed to be 120 mm and 220 mm,respectively.To improve the cutting ability of the poking roller on the crushed cornstalks,the outer edge of the poking plate was specifically designed to the tooth shape;furthermore,the tooth depth (h)was 35 mm,and the tooth width (w)was 30 mm,corresponding to a crushed stalk length of 30-50 mm.

Fig.4 Schematic illustration of poking roller structure

The formula to calculate the poking efficiency of the poking roller is as follows

(1)

WhereQis the discharge efficiency of the poking roller,m3/h;L,length of the poking roller,m;D,outer diameter of the poking roller,m;d,inner diameter of the poking roller,m;andn,speed of the poking roller,r/min.

Furthermore,

(2)

Whereηis the discharging efficiency of the crushed cornstalks,kg/h;ρ,bulk density of the crushed cornstalks,kg/m3(ranging from 35 kg/m3to 120 kg/m3),which was set to 50 kg/m3in this study[12].

Based on the design requirements in Table 1,the maximum stalk delivery efficiency was 1.8 t/h.Therefore,the maximum rotation speed of the poking roller was calculated to be 28.57 r/min using formulas (1)and (2).This should sufficiently increase the rotation speed of the poking roller to ensure maximum discharge efficiency;hence,the maximum value ofnwas set to 35 r/min,considering the effect of the stalk filling degree of the poking roller.Moreover,the rotation speed of the poking roller remained low,although it was set to the maximum.Hence,the tangential force of the poking teeth was relatively small,thereby preventing the scattering of crushed cornstalks and subsequently affecting the uniformity and stability of the discharge.Thus,the design requirements were satisfied[13].

As shown in the shaded part of Figure 5,the eccentric distancee0,labeled asOA,was set to 10 mm,whereas the initial phase ∠OABwas set to 45°.

Fig.5 Sweeping area of cross section of poking roller

When the discharge was not timely or the moisture content of the crushed cornstalks was extremely high,they squeezed against each other,increasing the adhesion force among them and decreasing fluidity,both of which prevented the shifting of the poking roller.To improve its adaptability to complex operating conditions,we designed an eccentrically rotating poking roller that increased the sweeping area of the poking teeth when it turned to the main shifting area.

1.2.3 Belt conveyor design

The belt conveyor is an important piece of equipment,particularly for the delivery of crushed cornstalks relative to this study.A belt conveyor with a conveying width of 800 mm and an apron height of 100 mm was selected.The crushed cornstalks were extracted by the poking roller;subsequently,they fell onto the conveying belt and were output as a stalk layer with a certain thickness at a constant speed equal to that of the belt.Because the poking speed was high and the moving speed of the belt was low,timely delivery could not be achieved.However,if the conveying belt offers rapid delivery,then the stalk flow will be interrupted and the material layer will possess low quality.Therefore,to obtain a better material layer that is uniformly thick and to realize continuous material flow,the rotation speed of the poking roller must be matched reasonably well with that of the belt conveyor.For convenient statistical analyses of the data,the ratio of the peripheral velocity of the poking roller to the linear velocity of the belt (hereinafter referred to as the speed ratio)was selected as the influencing factor.

Therefore,after determining the parameters of the stalk crushing device and the feeding conditions,it was revealed that the eccentric distance,rotation speed of the poking roller,and speed ratio contributed primarily to the conveying performance of the crushed stalk.

1.3 Simulation platform construction

Discrete element simulation software EDEM was used to conduct the simulation and optimization analysis of the poking and conveying process.This was performed to determine the effects of the eccentric distance,rotation speed of the poking roller,and speed ratio on the operating performance of the stalk discharging device;determine the optimal parameter combinations;avoid blindness of device trial production;and reduce cost.A model depicting the interaction between the discharging device and crushed cornstalks was established to simulate the actual operating environment and select the delivery efficiency and variation coefficients of width as evaluation indicators to prepare for subsequent analyses.This was performed to investigate the effects of the factors on the operating performance of the device.

Prior to performing the simulation,it is necessary to establish the geometric model of the device and complete the preprocessing parameter settings,such as those of the contact and particle models.

1.3.1 Particle model

In this study,cornstalks,including cornstalk branches and leaves,were crushed using a dual-roller crushing device for raw materials.Random sampling revealed that more than 90% of the crushed cornstalks were less than 50 mm in length with a moisture content of 34.68%.A vernier caliper was used to measure the crushed corn stalks several times,and two sizes of quadrilateral stalks were selected for the particle model.The length,width,and thickness of the two-particle models were 24 mm×15 mm×5 mm and 40 mm×10 mm×5 mm,respectively.The 3D model of the crushed cornstalks was established using SolidWorks and then imported into EDEM in the “.stp”format.In EDEM,the “.stp”model was filled via multi-ball superposition to obtain a discrete element model of the crushed stalk.The physical and particle models of crushed corn stalks are shown in Figure 6.

(a)Crushed cornstalks

1.3.2 Parameter setting of contact model between materials

During operation,the contacts among the crushed cornstalks,vibrating plate,poking roller,and belt were modeled using the Hertz-Mindlin non-sliding contact model.The relevant parameter settings are listed in Table 2[14-17].

Tab.2 Parameter setting of contact model between materials

1.3.3 Verification and optimization of contact parameters

The crushed cornstalks were granular and exhibited a certain degree of liquidity.The contact parameter setting used between crushed cornstalks and the material significantly affected the simulation results.Considering the effects of the crushed cornstalk properties,such as the length and moisture content as well as the indicated surface roughness of the material on the contact parameters of the materials,the model parameters in Table 2 were first carried out to simulate the repose angle and compared with the actual repose angle test results before simulation test of crushed straw conveying[18].

First,the natural falling method was used to test the actual repose angle of the crushed cornstalks crossing the stainless-steel conical barrel (Figure 7(a))[19].The test was performed five times,and the average value of these results was used for subsequent analyses.As shown in Figure 7,the actual repose angleθ1of the crushed cornstalks was measured to be 49.3°.The same operating conditions were simulated in EDEM.The error between the actual repose angle and simulated deposition angle was compared and analyzed to further correct the friction coefficient and restitution coefficient in order to improve the accuracy of the simulation.Based on the parameter settings of the contact model,as shown in Table 2,the measured simulation repose angleθ2was 20.6°,and the error was 57.98%.After optimizing the restitution coefficient and the rolling friction coefficient,the deposition accumulation angleθ3was 48.3°,and the error was 2.02%,indicating high simulation accuracy.Meanwhile,the static friction coefficient (interaction with cornstalk)was 0.44,and the rolling friction coefficient (interaction with cornstalk)was 0.38,as shown in Table 2.

Fig.7 Repose angle of crushed corn stalks1.Funnel 2.Accumulative floor

1.4 Test methods

First,simulation tests were performed;subsequently,physical tests were developed.The effect of each factor on the assessment index was analyzed via a single-factor simulation test,and the appropriate range was determined.Subsequently,the best parameter combination was determined via an orthogonal test.In the simulation test,the rate at which the particle factory produced crushed cornstalk particles was set to 0.5 kg/s.The initial falling velocity when the particles were generated was set to 0.5 m/s.Eulerian time integration was used,and the fixed time step was 10%.The crushed cornstalks were deposited in the surge bin 2 s prior to the simulation time,then the poking roller and conveyor belt began operating.Data collection was performed 5 s after commencing the simulation test.The percentage of time step was set to 15%,the output time step was 0.01 s,and the total simulation time was 15 s.

The crushed cornstalk delivery efficiency and the coefficient of variation were selected as the test evaluation indicators.Delivery efficiency is expressed as the ratio of the total mass of cornstalks delivered by the belt conveyor to the time consumed.The coefficient of variation is a parameter that characterizes the uniformity of the crushed cornstalks.As depicted in Figure 8,a 1 000 mm×800 mm area on the conveyor belt was selected as the test area and segregated into 20 sampling cells (4×5).

Fig.8 Schematic of sampling

Several cells were randomly selected from 20 sampling units,and the quality of materials in the cells were measured.Subsequently,the coefficient of variation was calculated.The formula for calculating the variation coefficient is as follows

(3)

(4)

(5)

Using the EDEM software,the quality of broken straw can be obtained directly using the post-processing module setting of the “Grid Bin Group”.

Pretests indicated that the stalk crushing device satisfied the design requirements shown in Table 1.Therefore,the straw crushing test simulation was not performed in this study;instead,the interaction between conveying components and the crushed cornstalks was investigated.During the simulation,the straw crushing device was omitted,and the vibration device and power transmission mechanism were simplified.The physical mechanism was replaced by the motion parameter setting in the EDEM software.SolidWorks was used to build the simulation device,which was then imported into EDEM in the “.stp”format[20].The simulation device model is shown in Figure 9.

Fig.9 Simulation device model1.Mass flow sensor 2.Cornstalks 3.Vibrating plate 4.Poking roller 5.Belt conveyor

As shown in Figure 9,the Grid Bin Group in the EDEM post-processing module segregates the crushed cornstalks covering the region on the conveyor belt into several areas.The mass flow sensor measures the weight of the crushed cornstalks in each area to calculate the coefficient of variation.The delivery efficiency is calculated as the ratio of the total mass of delivered cornstalks to the simulation time.

2 Results and analysis

2.1 Single-factor tests

To determine the range of various factors in the orthogonal tests,single-factor simulation tests at different levels for the three following factors were initially conducted:roller speed,eccentric distance,and speed ratio.According to the theoretical calculation results in Section 2,the eccentric distance,poking roller speed,and speed ratio ranged from 0 to 10 mm,0 to 35 r/min,and 0.8 to 1.2,respectively.In the single-factor test,other factors were set to intermediate levels.The simulation results (delivery efficiency and coefficient of variation)were obtained during EDEM post-processing,and Origin software was used to provide illustrations.

2.1.1 Effect of roller speed on delivery performance

During the delivery of crushed cornstalks,the speed of the poking roller directly determines the delivery efficiency.The effect of roller speed on the delivery efficiency and uniformity of the discharge is shown in Figure 10.Considering speeds up to 30 r/min,the higher the roller speed,the higher is the delivery efficiency.However,when the roller speed exceeded 30 r/min,the increment in delivery efficiency declined,even when increasing the speed continuously.This was because when the roller rotated at a low speed,the space between the poking plates was relatively filled with cornstalks each time the poking roller rotated;therefore,the delivery efficiency increased significantly as the rotation speed increased.In contrast,at high rotation speeds,when the stalk filling between poking plates decreased,the increment in delivery efficiency reduced.Compared to the coefficient of variation,the roller speed exerted a more significant effect on the uniformity of the crushed cornstalk delivery.When the speed was low,the coefficient of variation was high and the uniformity deviated,whereas a high speed improved the uniformity of delivery.Based on this analysis,the delivery amount increased with speed;therefore,when the speed of the belt conveyor remained constant,the amount of crushed cornstalks per unit area increased,reducing the weight difference in various regions.Consequently,the coefficient of variation decreased.

Fig.10 Effect of roller speed on delivery performance

2.1.2 Effect of eccentric distance on delivery performance

As shown in Figure 11,the delivery efficiency of the crushed cornstalks increased gradually with the eccentric distance.An eccentric distance of 8 mm to 10 mm yielded the highest delivery efficiency,followed by the eccentric distance of 4 mm to 8 mm.The eccentric distance of 0 to 4 mm presented the least increment in delivery efficiency.This is because when the eccentric distance increases,the swing amplitude of the vibrating plate increases,thereby effectively promoting the flow of crushed cornstalks and the filling of more crushed cornstalks in the poking plates.Therefore,at a constant speed,an increase in the eccentric distance can effectively improve delivery efficiency.However,when the difference remained within 1%,the eccentric distance did not significantly affect the uniformity of delivery,based on the coefficient of variation.This is because although the vibration of the vibrating plate can promote the flow of crushed cornstalks,the mixing effect still requires improvement.

Fig.11 Effect of eccentric distance on delivery performance

2.1.3 Effect of speed ratio on delivery performance

When the rotation of the poking roller is set to a constant speed of 30 r/min,the speed ratio can be changed by adjusting the rotation speed of the belt conveyor.The effect of speed ratio on the delivery performance of crushed cornstalks is shown in Figure 12.When the speed ratio increased from 0.6 to 1.8,the maximum and minimum delivery efficiencies were 14.1 kg/min and 13.82 kg/min,respectively,translating to a difference of approximately 2%.This suggested the insignificant effect of changing the speed ratio on the delivery efficiency of the crushed cornstalks,supported by the fact that altering the speed ratio did not change the rotation speed of the poking roller.The maximum and minimum coefficients of variation were 16.21% and 14.52%,respectively,translating to a difference of approximately 10.43%.The minimum coefficient of variation was observed at a speed ratio of approximately 0.9.It was evident that the speed ratio significantly affected the uniformity of the delivered crushed cornstalks.Reasonably matching roller and belt conveyor speeds reduced the coefficient of variation and improved the uniformity of the delivery.

Fig.12 Effect of speed ratio on delivery performance

2.2 Orthogonal tests

An L9(34)orthogonal test table was used in the simulation test to investigate the effects of structural parameters on the delivery performance and to determine the optimal combination[21].After comprehensively considering the single-factor test results,the eccentric distance,roller speed,and speed ratio of 3 mm to 9 mm,25 r/min to 45 r/min and 1 to 1.4 were set,respectively.The factor levels are listed in Table 3.The coefficient of variation and delivery efficiency were selected as the test indicators.The test results and analysis of variance are shown in Table 4,whereA,B,andCindicate the test factors.

Tab.3 Orthogonal test factors and levels

The test programs and results of the range analysis are shown in Table 4;variance of the simulation test results was analyzed by SPSS software,as shown in Table 5.

Tab.4 Test results and range analysis

Tab.5 Variance analysis result of orthogonal test

The roller speed significantly affected the delivery efficiency index.Based on the results of the range and variance analyses,the eccentric distance had a significant effect,unlike the speed ratio.The primary and secondary factors affected the delivery efficiency in the following order:A>B>C.The best combination wasA3B2C2,i.e.,a roller speed of 40 r/min,an eccentric distance of 6 mm,and a speed ratio of 1.2.

Considering the coefficient of variation,results of the range and variance analyses indicate that both the roller speed and speed ratio significantly affected the coefficient of variation,unlike the eccentric distance.The primary and secondary factors affected the coefficient of variation in the following order:C>A>B.The best combination wasC1A2B3,i.e.,a roller speed of 30 r/min,an eccentric distance of 9 mm,and a speed ratio of 1.

Two superior combinations were obtained from the two performance indicators of delivery efficiency and coefficient of variation,i.e.,program 1 (A3B2C2)and program 2 (C1A2B3),where the latter afforded a delivery efficiency of 33.33 m3/h and a coefficient of variation of 11.61%.Program 1 (A3B2C2)was replicated thrice,with an average delivery efficiency and a coefficient of variation of 35.67 m3/h and 12.76%,respectively.By comparison,the delivery efficiency of both programs reached 30 m3/h.However,compared with the design values,the delivery efficiency and coefficient of variation of program 2 were 7.8% and 1.15% larger than those of program 1,respectively.

Because the primary design purpose of the device is to achievea uniform and stable cornstalk delivery,ensuring the uniformity and continuity of crushed cornstalk delivery is the main consideration based on the design requirements of delivery efficiency.Hence,the closer the delivery efficiency is to the design purpose,the smaller should be the coefficient of variation,which is preferable and reflects the ideal effect on delivery.Therefore,after comprehensive considerations,the optimal combination was determined to be program 2 (C1A2B3),i.e.,a roller speed of 30 r/min,an eccentric distance of 9 mm,and a speed ratio of 1,which afforded a delivery efficiency of 33.33 m3/h and a coefficient of variation of 11.61%.

2.3 Verification test

Based on the simulation and optimization results of the structure parameters of the conveying mechanism,the stalk crushing and conveying test bench trial was performed,and a verification test was conducted.The test bench was designed by Nanjing Institute of Agricultural Mechanization,Ministry of Agriculture and Rural Affairs and processed by Jiangsu Hehai Water Supply and Drainage Complete Equipment Co.,Ltd.Bench tests were conducted in Taixing City,Jiangsu Province,in November 2019.The test material comprised of cornstalks crashed in bundles with an average moisture content of 39.7%.During the experiment,the cornstalks were manually placed on the harvest cutting table and delivered to the crusher.The quality of corn was counted after crushing per 15 minutes.Based on the principle shown in Figure 8,the coefficient of variation was calculated by random sampling.The parameters of the straw conveying and discharging device were optimized based on the results:a poking roller speed of 30 r/min,an eccentric distance of 9 mm,and a speed ratio of 1.The test was repeated five times,the results were shown in Table 6,and the average value was used.

The field test and its effect are shown in Figure 13.The test result indicated an efficiency of 37.09 kg/min,which implies an error of 11.28% compared with the optimized simulation result;the coefficient of variation was 13.77%,whereas that of the optimized simulation result was 18.6%.This was because the feeding speed during the field test was significantly affected by human factors and broken straw;therefore,the accuracy of the parameter setting achieved during simulation could not be ensured.However,the errors were within the acceptable range and satisfied the design requirements,thereby verifying the feasibility of the parameter combination and accuracy.

Tab.6 Results of verification test

Fig.13 Verification experiments of optimal parameters for conveying device1.Crusher 2.Harvest cutting table 3.Conveying device 4.Belt conveyor

3 Conclusion

1)To address the problems of low efficiency and poor uniformity in crashed straw conveying,a design method combining a vibration plate and poking roller discharge was proposed.A straw crushing and conveying device was designed,and the main structural parameters of the conveying device were obtained through theoretical calculations.

2)Using the discrete element software EDEM,single-factor and orthogonal experiments of crashed cornstalk conveying were simulated to investigate the effects of operation parameters on conveying performance.The optimal combination of structural parameters was determined,and a reference for prototype production was provided.Simulation test results indicated that the poking roller speed and eccentric distance significantly affected the conveying efficiency,unlike the speed ratio.The poking roller speed and speed ratio significantly affected the coefficient of variation,unlike the eccentric distance.The optimal parameter combination selected based on the simulation results was as follows:a roller speed of 30 r/min,an eccentricity of 9 mm,and a speed ratio of 1.Using these parameters,optimal straw conveying performance was achieved.

3)Based on the optimized simulated test results,a straw crushing and conveying device was developed,and actual verification tests were conducted.The field test results indicated a conveying efficiency of 37.09 kg/min and a coefficient of variation was 13.77%.Results of comparative tests indicated the feasibility and high accuracy of the optimized results of the EDEM software.