Optimization Design of an Alfalfa Seed Airflow Collection and Drainage System Based on Numerical Simulation
Round 1
Reviewer 1 Report
The paper deals with the design and optimization of an Alfalfa seeding device. An auger conveyer with/without a churning wheel delivers seeds into the venturi tube wherein airflow delivers the seeds to the distribution assembly.
1. The introduction is missing the state-of-the-art review of contemporary seeding devices which are used for alfalfa with the appropriate references.
2. References for CFD-DEM simulation method are given just as "[4-20]", without particular comments and some of the references are not relevant for the topic of this paper.
3. Background (and references) for the simulation analysis of seed flow through the screw conveyor should be added.
4. CFD-DEM simulation is not a novel procedure and neither is modeling machinery with ADAMS. So, it is crucial to clearly state what is the main contribution of this research!
5. Paragraph 2.2, Fig.3. must be explained: what are points P, H and M, equation (2) - what is uo in equation (2) etc?
6. Please, explain what references [22], [23] and [27] are!
7. The adoption of time parameters for the EDEM and ADAMS Co-Simulation Test as well as the CFD-DEM Coupled Simulation Method should be explained better.
8. The shape of the venturi ejector is obtained for inlet air pressure set to 3kpa, and the seed feeding efficiency 5g/s - shape A. What will happen for some other combination of pressures and seed feeding speed?
9. Optimization (paragraph 5.) - what is the shape of the venturi ejector? Also, values for pressure and seed feeding speed are significantly smaller in comparison to those stated in paragraph 4., please explain!
Author Response
Reply to Reviewer 1:
The author would like to thank this reviewer for his/her critical reading and expert comments on the manuscript. The comments were of great help for further improvements and the revisions were marked in blue in the revised manuscript. Below, we will address the reviewer’s concerns point-to-point:
Comments and answers:
The paper deals with the design and optimization of an Alfalfa seeding device. An auger conveyer with/without a churning wheel delivers seeds into the venturi tube wherein airflow delivers the seeds to the distribution assembly.
Point 1: The introduction is missing the state-of-the-art review of contemporary seeding devices which are used for alfalfa with the appropriate references.
Response 1: We fully agree with the reviewer that there is no description of the research status of alfalfa seed metering device in the abstract. Therefore, some sentence are included in the abstract to clearly indicatethe state-of-the-art review of contemporary seeding devices as followed: “Zhao [4] designed a small mountain alfalfa seed drill, using shaped hole wheel metering device, its each line displacement consistency coefficient of variation is 4.09%. Zhai [5] designed a multi-line with one-device type forage seeds metering device, basing on the mechanical and physical properties study of forage grass seeds, it was composed of adjustable screw，stirrer，metering device housing and central metering sheave and so on, the sowing rate can be set by turning the screw to change working length of central metering sheave relative to metering device housing, the stirrer inside of the sheave housing was used to prevent seeds overhead, and metering of different sizes of seed was adjusted by changing the position of internal components of slot wheel mechanism．Yin [6] added a seed filling brush in the outer grooved wheel seed metering device box and removed the seed metering tongue, based on the study of the working process of the seed metering device, in order to meet the requirements of actual seeding amount. Zhao [7] designed a kind of seed metering device with spiral external grooved wheel, The seed output per rotation of the spiral outer grooved wheel is far less than that of the ordinary outer grooved wheel, and the range of change in the seed amount adjustment is small, but the seed amount is relatively stable, which is suitable for sowing small grains such as alfalfa, bermuda root, rape, etc.”.
Point 2: References for CFD-DEM simulation method are given just as "[4-20]", without particular comments and some of the references are not relevant for the topic of this paper.
Response 2: Thank you for pointing out the inappropriate description about the DEM-CFD research status. In response to your suggestion, some sentences are included in the abstract as“Yang [12] carried out the numerical analysis of particle movement of fertilizer separating device through the coupling simulation method of discrete element method and computational fluid dynamics. Han [13] used the EDEM-CFD coupling analysis method to optimize the structure of the internal inflatable seed metering device. Ding [14] used the coupling method of discrete element and computational fluid dynamics to simulate the working process of the air suction seed metering device, and analyzed the drag force and movement speed of the seed. Siamak [16] simulated the cuttings transport considering the dynamic collision process using a coupled Computational Fluid Dynamics and Discrete Element Method (CFD-DEM).”in the revised manuscript. At the same time, unrelated literature has been deleted.
Point: Background (and references) for the simulation analysis of seed flow through the screw conveyor should be added.
Response 3: Thank you for the expert comments. In response to your suggestion, background and references for the simulation analysis of seed flow through the screw conveyor has been added as followed“However, in the air flow collection and drainage system, the mechanical seed feeding device usually uses the external grooved wheel seed metering device. Due to its own structural characteristics, the seed flow pulse usually occurs during the seed feeding process, which leads to the increase of the coefficient of variation of the consistency of the discharge capacity of each row of the collection and drainage device. The screw feeder has the advantages of simple structure and steady flow transportation, and is often used as the core component of wheat and rice seed metering device. Mei [8] designed a seed metering device with spiral tube scooping for rice and wheat , its main components include seed feeding tube, front, middle and rear shells, central shaft, seed chamber, seed bailing tube assembly fixed disk, seed outlet hole length adjustment block, seed metering tube, base, and spiral seed bailing tube assembly. Pan [9] based on the external grooved wheel seed metering device, a rice precision direct seeding spiral grooved seed metering device is designed. The seeds enter into the spiral groove under their own gravity and the interaction force between the seeds. With the rotation of the seed metering wheel, the surplus seeds are brushed back to the seed filling area by the seed brush. The seeds in the spiral groove are protected by the seed guard plate. When they turn through the seed protection area, they fall down to realize sowing. In the field of simulation optimization, Wu [10] carried out a simulation experiment on the conveying process of the grain conveyor by using the software of EDEM and orthogonal test method. According to the principle of least square method, the response surface model of conveying capacity and energy dissipation index was constructed by MATLAB data fitting program, and the influence relationship between structural parameters and operating parameters of vertical screw conveyor on performance index was obtained. Guo [11] Established the discrete element model of the screw conveyor,and simulated the process of conveying rice by the screw conveyor by using the EDEM software, taking the 20°inclined screw conveyor as an example, the optimal combination of the inclined screw conveyor is obtained by using orthogonal experiments.“
References:
Mei, Z.X.; Xia,J.F.; Zhang, J.M.; Du,J.; Yang,Q.; Hu, M.J.; Luo, S.C.; Liu, Z.Y.; Li, Z,Y. Seeding performance of seed metering device with spiral tube scooping for rice and wheat. Journal of Huazhong Agricultural University. 2020, 39(5), 136-146.
Pan, X.J.; Dong, Z.Y.; Li, Y.; Li, C.; Bai, M,C.; Yang, S.; Design and optimization of rice spiral groove seed metering device. Jiangsu Agricultural Sciences. 2020, 48(17), 233-239.
Wu, Z.Y.; Cheng, Y.Y.; Gao, M.Y.; Zhang, Y.X.; Zhang, Z.X.; Performance Analysis of Grain Vertical Screw Conveyor Based on EDEM. Sci-Tech Innovation & Productvity. 2022, 3, 62-64.
Guo, C.; Pu, X.L.; Numerical Simulation Analysis for Screw Conveyor Based on EDEM. Journal of Yanbian University (Natural Science). 2018, 44(2), 179-182.
Point 4: CFD-DEM simulation is not a novel procedure and neither is modeling machinery with ADAMS. So, it is crucial to clearly state what is the main contribution of this research!
Response 4: We fully agree with the reviewer that CFD-DEM simulation is not a novel procedure and neither is modeling machinery with ADAMS. In order to improve the working performance of alfalfa pneumatic header, we innovatively combined the horizontal screw conveyor with the pneumatic header, and added a stirring device. At present, the same structure has not been found in related fields. We used the EDEM software and ADAMS software to jointly simulate the working process of the horizontal screw conveyor, and obtained the influence of the seed mixing mechanism on the population movement characteristics, population force, seed mass flow rate at the seed drop mouth and coefficient of variation of various indicators. The results show that the seed mixing mechanism can effectively improve the population mobility, reduce the local dead zone of the population, increase the material filling coefficient between the spiral blades, and the horizontal screw conveyor with seed mixing function has higher conveying efficiency and better conveying uniformity. In addition, in order to optimize the structural parameters of the Venturi ejector diffusion tube and improve the efficiency and uniformity of seed metering, EDEM software and Fluent software were used to jointly simulate the seed feeding process, and finally the optimal working parameters and structural parameters were obtained. In this study, the traditional numerical simulation method was used to reveal the working mechanism of the screw conveyor with seed mixing function, explore the reasons for the good flow uniformity of the seed flow, and optimize the overall parameters of the collection and drainage system. The results of this study can provide a theoretical reference for improving the performance of forage seeds and other small grain seeders.
Point 5: Paragraph 2.2, Fig.3. must be explained: what are points P, H and M, equation (2) - what is uo in equation (2) etc?
Response 5: Thank you for the expert comments.We are sorry for causing the confusion. P. H and M are the focal points between auxiliary lines in the process of analyzing the movement direction of seed particles, which have no practical significance. To avoid ambiguity, we have deleted them in Figure 3. uo in equation (2) is the friction coefficient between seed and helical surface.
Point 6: Please, explain what references [22], [23] and [27] are!
Response 6: Thank you for pointing out the false description in references, the format of these three references is wrong. We have revised them as followed.
Zhang, D.H. The optimization research of screw conveyor. 2006, Dalian University of Technology
Xia, R.X. The research on mining truck loading process using EDEM and ADAMS joint solution. 2015, Northeastern University.
Lei, X.L. Design and working mechanism of air-assisted centralized metering device for rapeseed and wheat. 2017,Huazhong Agricultural University.
Point 7: The adoption of time parameters for the EDEM and ADAMS Co-Simulation Test as well as the CFD-DEM Coupled Simulation Method should be explained better.
Response 7:Thank you for pointing out the inappropriate description of time parameters in two simulation tests. We have supplemented the following descriptions in the corresponding paragraphs of the paper.“In the spiral conveying simulation experiment, the EDEM simulation time step is 6×10 - 6 seconds, and the simulation time is set as the 3rd second. Considering that the particle movement reaches a stable state, the ADAMS simulation time step should be an integral multiple of the EDEM time, so it is set to 3×10 - 5 seconds. After the simulation test starts, record the seed mass flow rate every 0.01 second.The test effect is verified at the 3rd second. In the venturi simulation test, we set the EDEM time step to 1×10 - 6 seconds, and the Fluent time step to 5×10 - 5 seconds, which is 50 times of the EDEM; Set the number of Fluent steps to 60000, the simulation time is 3 seconds; Set each time step to iterate 50 times at most; To extract particle motion information as detailed as possible, data is saved every 0.01 seconds in EDEM and Fluent. The test effect is verified at the 1st second. “
Point 8: The shape of the venturi ejector is obtained for inlet air pressure set to 3kpa, and the seed feeding efficiency 5g/s - shape A. What will happen for some other combination of pressures and seed feeding speed?
Response 8:Thank you for the expert comments. In order to explore the effect of different shape parameters of the Venturi tube on the pressure and velocity changes in the internal flow field of the tube, as well as the speed and force of the seed particles, we selected two variables, namely, the limited inlet pressure of the tube and the seed feeding rate. Based on the optimized shape of the venturi, in the subsequent actual test, we conducted the delivery performance of the venturi under different inlet pressure (0.8~2.4kPa) and different seed feeding efficiency (0.6~2.2g/s), and obtained an ideal combination of parameters. The purpose of this research method is to improve optimization efficiency. As mentioned in your suggestion, the optimization test in this article has some limitations, which is also the research we will carry out next.
Point 9: Optimization (paragraph 5.) - what is the shape of the venturi ejector? Also, values for pressure and seed feeding speed are significantly smaller in comparison to those stated in paragraph 4., please explain!
Response 9: Thank you for pointing out the adequate description of the parameters about shape, pressure and seed feeding speed in paragraph 4. and paragraph 5. The shape parameters of the venturi ejector in paragraph 5. is consistent with the shape parameters of type A injector in the numerical simulation test, which the diffusion angle is 5°, the diffuser length is 200mm, and the length of mixing pipe is 50mm. The reason for this setting is to compare the effect of actual test and simulation test and verify the rationality of DEM-CFD simulation method. When the pipe diameter is the same, the air flow velocity is 30m/s, and the corresponding air flow pressure is 3kPa; In addition, according to the calculation of the average seed weight of alfalfa seeds, the feeding efficiency of 5g/s is equivalent to feeding 780 seeds per second, so the two parameter settings in the preceding and following articles are consistent. Thank you for finding these description ambiguities, which have been reflected in the revised version.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Transport and separation of granular mixtures in pneumatic channels requires uniformity in channel loading. The authors designed an innovative seed feeding system, performed simulation and verification tests on a real model.
I have serious doubts about the interaction of two elements of the mechanism: a mechanical stirrer and a screw. Do these elements damage the seeds? Does mechanical friction increase over time? Has it been tested?
There is also the question of whether the venturi ejector would not be better placed in the vertical section of the pipeline?
Detailed comments:
(1) The title of the work is too broad; in addition, keywords should not duplicate title phrases.
(2) Physical units should be consistently written exponentially in both text and drawings.
(3) Conclusions should synthetically emphasize the obtained results of research and development works. It is unnecessary to repeat the purpose of the work and the methods used.
Author Response
Reply to Reviewer :
The author would like to thank this reviewer for his/her critical reading and expert comments on the manuscript. The comments were of great help for further improvements and the revisions were marked in blue in the revised manuscript. Below, we will address the reviewer’s concerns point-to-point:
Comments and answers:
Transport and separation of granular mixtures in pneumatic channels requires uniformity in channel loading. The authors designed an innovative seed feeding system, performed simulation and verification tests on a real model.
Point 1: I have serious doubts about the interaction of two elements of the mechanism: a mechanical stirrer and a screw. Do these elements damage the seeds? Does mechanical friction increase over time? Has it been tested?
Response 1: Thank you for pointing out the deficiencies in this study. Considering the problem of seed damage caused by mechanical extrusion, we have appropriately increased the gap between the seed mixing mechanism and the screw conveying mechanism in the design stage to ensure that the seed group has enough flow space. However, due to the defects of mechanical structure, some parts will inevitably be damaged due to extrusion. According to the actual supplementary test results, the damaged seeds accounted for 3% in the continuous 10min seed supply test. In the next stage of research, we will focus on solving the problem of mechanical wear, such as using flexible materials to process the seed mixing mechanism, and conducting structural optimization tests based on the damage rate.
Point 2: There is also the question of whether the venturi ejector would not be better placed in the vertical section of the pipeline?
Response 2: Thank you for your inspiration to us in the placement of Venturi ejector.In this study, the reason why we placed the Venturi ejector horizontally is that after the seed flow is accelerated in the Venturi ejector, it needs to pass through the seed delivery elbow and the corrugated reducer before reaching the distributor for distribution. In this process, due to the effects of air flow disturbance and pipe wall collision, the seeds will have enough kinetic energy and be in a relatively uniform distribution state, which will help improve the distribution uniformity of the air flow collection and exhaust system. If the Venturi ejector is placed vertically, although some power consumption can be saved, the seeds will enter the bellows without passing through the seed conveying elbow stage, which will be detrimental to the uniform distribution of seeds in the pipeline.Of course, this is only a theoretical analysis. We are very interested in the placement direction of the ejector you suggested, and we are ready to verify your proposal through numerical simulation.
Point 3: The title of the work is too broad; in addition, keywords should not duplicate title phrases.
Response 3: We fully agree with the reviewer that the title and phrases are not suitable, in response to your suggestion, the title was changed to“Optimization Design of Alfalfa Seeds Airflow Collection and Drainage System Based on Numerical Simulation“, and the keyworks were changed to“seeding device; pneumatic; EDEM; Fluent; Adams“.
Point 4: Physical units should be consistently written exponentially in both text and drawings.
Response 4: Thank you for pointing out the wrong description about the physical units, and we have conducted full text inspection and modification for this problem.
Point 5: Conclusions should synthetically emphasize the obtained results of research and development works. It is unnecessary to repeat the purpose of the work and the methods used.
Response 5: Thank you for pointing out the inappropriate description about the conclusions, in response to your suggestion, the conclusions were changed to “A kind of horizontal screw conveyor with seed mixing function was designed to improve the uniformity of air conveyed alfalfa seed collection and exhaust. EDEM software and Fluent software were used to jointly simulate the seed feeding process of Venturi injector. The influence of the structure parameters of the diffuser on the working performance of the ejector was analyzed based on the changes of the pressure and velocity of the flow field inside the pipe, the velocity and force of the seed particles. The results showed that when the diffusion angle was 5 °, the length of diffusion section was 200 mm, and the length of mixing section was 50 mm, the pressure loss of Venturi ejector was the minimum, the outlet air velocity was the maximum, the uniformity of seed supply was the best, and the seed supply efficiency was the highest. With the inlet air pressure and particle feeding efficiency as the test factors, and the coefficient of variation of the ejector discharge as the test index, the two factor five level all factor test was conducted, and the range and variance analysis were conducted. The results showed that seed feeding rate and inlet wind pressure had significant effects on the coefficient of variation (P<0.05), while the interaction between them had no significant effect on the coefficient of variation (P>0.05); Compared with the particle feeding efficiency, the inlet air pressure has a more significant effect on the coefficient of variation of the displacement. The optimal working parameter combination is the inlet air pressure of 1.6 kPa and the particle feeding efficiency of 1.8 g/s.”
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
All the comments on the manuscript have been carefully considered and satisfactory explanations and adequate changes have been provided.
Still, there are typing and style language errors (some of them are listed bellow), so I strongly suggest proof reading and reediting of the manuscript. After that manuscript can be accepted for the publication.
The calculation formula is (0.2 ~ 0.35) l l d D = , considering the requirements of strength and stiffness, the design diameter of the rotating shaft is 8mm. - red text is marked as omitted but without that formula sentence has no meaning.
Import the established screw conveyor model into ADAMS, define the material properties of each component, and use Boolean operations to integrate the relatively static parts into one. Add a rotating pair to the auger and the churning wheel respectively, and add a contact between the two, and set the damping to 100. etc. - this paragraph is written in a manual style: Do that and that... which is inappropriate for journal writing style
The high-speed airflow enters from the nozzle inlet and joins the seeds at the shrinking tube, and the airflow inlet velocity is set to 3000Pa0m/s - red text is marked as omitted but velocity unit can not be pascal (Pa)
Author Response
Reply to Reviewer :
The author would like to thank this reviewer for his/her critical reading and expert comments on the manuscript. The comments were of great help for further improvements and the revisions were marked in blue in the revised manuscript. Below, we will address the reviewer’s concerns point-to-point:
Comments and answers:
All the comments on the manuscript have been carefully considered and satisfactory explanations and adequate changes have been provided.
Still, there are typing and style language errors (some of them are listed bellow), so I strongly suggest proof reading and reediting of the manuscript. After that manuscript can be accepted for the publication.
Point 1: The calculation formula is (0.2 ~ 0.35) l l d D = , considering the requirements of strength and stiffness, the design diameter of the rotating shaft is 8mm. - red text is marked as omitted but without that formula sentence has no meaning.
Response 1: Thank you very much for pointing out the error. We have added the calculation formula “dl=(0.2~0.35)Dl” to this description.
Point 2: Import the established screw conveyor model into ADAMS, define the material properties of each component, and use Boolean operations to integrate the relatively static parts into one. Add a rotating pair to the auger and the churning wheel respectively, and add a contact between the two, and set the damping to 100. etc. - this paragraph is written in a manual style: Do that and that... which is inappropriate for journal writing style
Response 2: Thank you for the expert comments. In response to your suggestion, the description in this paragraph is modified as "After the 3D model of the screw conveyor is imported into ADAMS software, the material properties of each part are defined, and the relatively static parts form an integral part through Boolean operation, so that only the auger and seed mixing wheel can rotate. In order to better simulate the real environment, the damping value of 100 is added between the auger and the seed mixing wheel."
Point 3: The high-speed airflow enters from the nozzle inlet and joins the seeds at the shrinking tube, and the airflow inlet velocity is set to 3000Pa0m/s - red text is marked as omitted but velocity unit can not be pascal (Pa)
Response 3: Thank you very much for pointing out the error. Here, the 3000Pa refers to the airflow inlet pressure, so we have changed the “velocity” to “pressure”.
