Installation and Advanced Method for the Evaluation of Air Velocity over the Sieves of the Cleaning Unit of Combine Harvesters

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript is within the scope of the Journal. The English language is satisfactory, and readers will understand the information presented. The provided information on the design and velocity adjustments of cleaning systems at the level of sieve surfaces for combine harvesting. The manuscript is properly organized and thus meet scientific merit. However, there are some issues to be addressed as follows:

1. Objectives: The objectives in lines 120-124 should be clearly stated to understand the purpose of the study. Please, avoid the usage of 'purpose and objectives' of the study.
2. - etc in line 124 is inappropriate. 
3. The caption in Table 1 should expanded for clarity. 
4. Results should be 'Results and Discussion' or a 'Discussion' section should be provided.
5. Please, provide adequate in-text citations or related works of other Authors in the 'Results and Discussion' section or a section as 'Discussion' to meet scientific discussion standard. 
6. Lines 345-356 present conclusion statements. Please, merge those information with the Conclusions.
7. Line 388 should not start with the 'In conclusion....''. Ensure that the Conclusions provide the specific findings of the study without any repetitions of the results and discussion. 
8. Please, the results of the measurements or determined parameters done in triplicate in a Table with standard deviation and % coefficient of variation. 

Author Response

Comments 1: Objectives: The objectives in lines 120-124 should be clearly stated to understand the purpose of the study. Please, avoid the usage of 'purpose and objectives' of the study.

Response 1: Thank you for pointing this out. We agree with this comment. We have modified the content of the aforementioned sentence, with the following text:  

”As a result, given the importance of grain cleaning systems in combine harvesters, through this scientific approach we set out to design and create an original methodology and installation for measuring the air flow velocity profile at the sieve surfaces according to the specific settings of the harvesting technologies of various agricultural crops, such as: fan speed, the position of the deflectors in the air exhaust duct and the opening of the louvers of the two sieves.”.

For detailed revisions, please refer to lines 125-130 on pages 3-4 of the revised manuscript.

Comments 2: - etc in line 124 is inappropriate. 

Response 2: Agreed. It was removed and the whole sentence was rephrased.

For detailed revisions, please refer to lines 125 on pages 3 of the revised manuscript.

Comments 3: The caption in Table 1 should expanded for clarity. 

Response 3: We agree with this comment. The following note was added to Table 1:  Note: vane df.1 directs the air flow towards the upper sieve and vane df.2 directs the air towards the lower sieve; the positions of the vanes are shown in Figure 3: A1 and A2 for the upper one (df.1); B1 and B2 for the lower one (df.2).

Please refer to Table 1, page 7.

Comments 4: Results should be 'Results and Discussion' or a 'Discussion' section should be provided.

Response 4: Agree. We modified the name of the "Results" section to "Results and Discussions"

Please refer to page 8, line 253.

Comments 5: Please, provide adequate in-text citations or related works of other Authors in the 'Results and Discussion' section or a section as 'Discussion' to meet scientific discussion standard. 

Response 5: Agree. We appreciate the valuable comments of the reviewers regarding the alignment of our results with the research in this field conducted worldwide. To address this request, we have included the following articles in the list of bibliographical references:

40. Li, D.; He, Q.; Yue, D.; Geng, D.; Yin, J.; Guan, P.; Zha, Z. Research experiment on airflow field control technology of harvester cleaning system based on load distribution, Agriculture2024, 14 (5), 779; https://doi.org/10.3390/agriculture14050779
41. Zhang, C.; Geng, D.; Xu, H.; Li, X.; Ming, J.; Li, D.; Wang, Q. Experimental Study on the Influence of Working Parameters of Centrifugal Fan on Airflow Field in Cleaning Room. Agriculture2023, 13, 1368. https://www.mdpi.com/2077-0472/13/7/1368
42. Yang, L.; Lizhang, X.; Ying, Z.; Baijun, L.; Zhenwei, L.; Yaoming, L. Effects of throughput and operating parameters on cleaning performance in air-and-screen cleaning unit: A computational and experimental study.  Electron. Agric.2018, 152, 141–148.https://doi.org/10.1016/j.compag.2018.07.019
43. Liu, P.; Jin, C.; Yang, T.; Chen, M.; Ni, Y.; Yi, X. Design and Experiment of Multi Parameter Adjustable and Measurable Cleaning System.  Chin. Soc. Agric. Mach.2020, 51, 191–201.

These papers were cited in the "Results and discussion" section, as follows:

” The results obtained and presented regarding the air flow velocity profile, for the conditions presented above, are also supported by various research conducted under laboratory conditions, on different experimental models [40,41]”. 

See manuscript page 8, lines 272-274.

” Therefore, the distribution and velocity of the air flow at the surface of the upper sieve, which determines the quality of the seed cleaning process, depends on the fan air flow, respectively, its velocity, the position of the deflectors, as well as the settings of the blinds of the two sieves, a fact demonstrated by other papers [42,43]”.

Details regarding the changes in the manuscript page 9 lines 294 -298.

 

”The distribution and velocity of the air flow at the surface of the upper sieve are parameters that are difficult to manage and regulate, while they have a major impact on the process of separating the mixture of seeds and MOG, aspects confirmed by other papers based on research carried out in laboratory conditions, using different experimental models and various simulation software [40-43]. Compared to the results obtained in the cited papers, which are based on experimental laboratory models, our research aims to test seed cleaning systems and MOG from real combines, used for harvesting cereals and technical plants. For these reasons, our research is original, and allows testing the performance of cleaning systems from any type of combine. ”

For details please check the manuscript page 12-13 lines 345-353.

Comments 6: Lines 345-356 present conclusion statements. Please, merge that information with the Conclusions.

Response 6: Agree. We have eliminated the sentences from lines 345-356 and introduced point 3 in the conclusions, regarding directions for the development of this research:

(3) The obtained results show the importance of this scientific endeavor and that, in the future, further studies and research are necessary, aiming to improve the the separation process of seeds and MOG.  In order to improve the uniformity of the air distribution at the level of the upper sieve surface the following directions must be taken into account: conducting comparative studies for different cleaning systems, equipped with different types of fans (centrifugal-tangential, axial and cross-flow); improving the desing of centrifugal-tangential type fans using variable suction sections; optimizing the construction of deflectors; improving the sealings of the cleaning system housings.

Please check the updated manuscript at page 15, lines 422-430.

Comments 7: Line 388 should not start with the 'In conclusion....''. Ensure that the Conclusions provide the specific findings of the study without any repetitions of the results and discussion. 

Response 7: Agree. We have removed this sentence to avoid redundancy with the rest of the conclusions. Please check the manuscript page 15.

Comments 8: Please, the results of the measurements or determined parameters done in triplicate in a Table with standard deviation and % coefficient of variation.

Response 8: Agree. Thank you for the proposal, it was welcomed. The standard deviation of the results was calculated and graphically represented in Figure 13a and Figure 13.b.

”The accuracy of the measurements is conditioned by the precision of the sensors with which the laboratory stand was equipped. For this purpose, statistical calculations were performed to determine the standard deviation. For the calibration of the anemometric sensors in the stand, the Testo 405i anemometer was used, which has an accuracy of ±0.1 m/s in the range 0 – 2 m/s and ±0.3 in the range 2 – 15 m/s, being used as a reference base. The number of 

individual measurements for each of the 52 measurement points on the surface of the sieve was 10.

 

 

Figure 13. Air flow velocity measured on the surface of the upper sieve and its standard deviation, with the deflectors in position B, with the upper sieve in position 3/4, with the lower sieve in position 1/2, and for the fan speed of: a - 400 (RPM); b - 800 (RPM); v – air flow velocity (m/s); 1, 2, 3, ..., 13 – air flow velocity measurement zones along the sieve; S1, S2, S3, S4 – anemometric sensors for measuring the air flow velocity in the transverse plane.

 

For these conditions, the average value of the velocity was calculated for each measuring point, and then the standard deviation was determined for each established position. The results obtained were represented graphically (Figure13), to make it easier to analyse. From the analysis of these results, it appears that the maximum value of the standard deviation of the anemometric sensors is 0.248 m/s, which is lower than the precision of the Testo 405i anemometer (of ±0.3 for the range of 2 – 15 m/s) used as a reference base. These results show us that the built stand and the research method were established correctly”.

For details, please check the manuscript on page 14, fig. 13.

 

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This article presents the installation and procedure for assessing the airflow velocity profile generated by the fan in the cleaning system of a New Holland combine harvester. The velocity profile was based on measurements taken at 52 points distributed across the entire surface of the upper and lower sieves, for various fan speeds, various air slat positions, and various sieve opening positions. The obtained experimental data were graphically presented using a Radial Basis Function (RBF) interpolation model, emphasizing that the airflow generated by the fan at the upper sieve level, in the longitudinal plane, and especially in the transverse plane, is unevenly distributed and depends on the fan impeller speed, the opening of the two sieve louvers, and the arrangement of the two deflectors. This concept and method of preparing the tests and measurements are valid. The research conducted is important because correct adjustment of the cleaning unit and correct assessment of the air velocity profile above the sieves result in reduced grain losses from the upper sieve due to grain flotation, reduced broken grain content in the grain tank due to reduced material flow from the auger, and reduced contaminant content in the tank.

The authors' research fills a research gap in the science of cleaning systems with louvered screens, thus complementing and expanding the current knowledge regarding the control parameters and airflow velocity values ​​generated by centrifugal fans.

 

The authors have addressed an exceptionally challenging research problem concerning traditional cleaning systems used in combine harvesters for a long time. The value of this article would be enhanced if the authors also included knowledge on innovative new solutions in grain cleaning, which use not only centrifugal fans but also axial fans. This would increase knowledge of cleaning problems and demonstrate the application of solutions that differ in grain cleaning technology and in combine harvester cleaning systems. I would suggest expanding the literature review to include the following:

1. DOI: 10.13031/trans.12110
2. DOI: 10.13031/trans.13575
3. https://doi.org/10.3390/pr8030346DOI: 10.13031/trans.12110

or others related to the development of cleaning systems in combine harvesters, for example:

4. https://www.sciencedirect.com/science/article/abs/pii/S1537511023002325#preview-secti

I have no comments on the research methodology or the way it was conducted. The text of the article is original and interesting to the reader. The authors answer the questions posed. The concept of the article is appropriate. In analyzing tire safety, the authors take into account tire design, material structure, the manufacturing process, tire stresses, and tire strength. The authors emphasize the research methods, summarizing the results of tests on the mechanical properties of DPO under various operating conditions.

The article is well-written and understandable, and will be of interest to readers, especially combine harvester users. Such original works are scarce because researchers are reluctant to address issues related to grain and seed cleaning. I congratulate the authors on their success in this research.

The conclusions are drawn from the text of the article and the research; I would only suggest adding conclusions regarding what was not achieved and conclusions regarding future research directions.

Author Response

Comments 1. I would suggest expanding the literature review to include the following: DOI: 10.13031/trans.12110; DOI: 10.13031/trans.13575; https://doi.org/10.3390/pr8030346; DOI:10.13031/trans. 12110, or others related to the development of cleaning systems in combine harvesters, for example: https://www.sciencedirect.com/science/article/abs/pii/ S1537511023002325#preview-secti

Response 1: Thank you for pointing this out. We agree with this comment. We have inserted the following text in the introduction:  

” part of the research carried out worldwide was on the conception, design and realization of various experimental models, based on other operating principles, such as those coordinated by Krzysiak, who experimented with an innovative mechano-pneumatic seed cleaning system with a rotating drum [26,27];”.

For detailed revisions, please refer to lines 104-107 on pages 3 of the revised manuscript.

Reviewer 3 Report

Comments and Suggestions for Authors

• Research methodology and measurement system
  The development of the research methodology and the design of a cost-effective yet efficient measurement system constitute a valuable contribution. However, it should be clarified what specific parameter serves as the key indicator of combine harvester performance — the uniformity of airflow velocity distribution or the efficiency of grain separation.

• Scope of experimental validation
  The experiments were conducted using only a single model of a combine harvester. The absence of a comparison with another model (e.g., from a different manufacturer) limits the generalizability and robustness of the results.

• Boundary conditions and model assumptions
  The assumption that the air velocity at the frame boundary equals 0 m/s requires further justification. Does the frame edge adhere perfectly to the channel wall through which the air flows? To strengthen model validation, it is recommended to experimentally introduce a non-zero velocity at the boundary and analyze the model’s behavior under such conditions.

• Influence of the measurement frame
  The measurement system frame appears to introduce additional airflow disturbances. The authors might consider reducing the number of rods, particularly the edge rods located near the channel wall, to minimize such effects.

• Asymmetry in airflow velocity
  The results indicate a slight difference in air velocity between the two sides of the frame. The cause of this discrepancy should be investigated — whether it is related to the combine’s structural design or to measurement system inaccuracies. It is suggested to swap the sensors to verify whether the difference persists.

• The manuscript should also include detailed information on the electric motor model and its parameters used in the measurement system.

 

The manuscript presents an interesting and practically relevant study on the development of a measurement system for assessing combine harvester performance. The approach demonstrates technical ingenuity and potential for real-world application. However, to improve scientific rigor and reproducibility, the study would benefit from additional validation experiments, clarification of boundary conditions, and discussion of possible measurement uncertainties. With these improvements, the paper could make a valuable contribution to the field of agricultural machinery and process monitoring.

Author Response

Comments 1: Research methodology and measurement system
The development of the research methodology and the design of a cost-effective yet efficient measurement system constitute a valuable contribution. However, it should be clarified what specific parameter serves as the key indicator of combine harvester performance — the uniformity of airflow velocity distribution or the efficiency of grain separation.

Response 1: Thank you for pointing this out. We agree with this comment. You have noticed very well that the seed and MOG cleaning system in the combines is based on a mechanical-pneumatic separation, so the efficiency of the separation depends largely on the velocity and uniformity of the air flow distribution, in this regard, we have inserted the following remark in the text:

” The distribution and velocity of the air flow at the surface of the upper sieve are parameters that are difficult to manage and regulate, while they have a major impact on the process of separating the mixture of seeds and MOG, aspects confirmed by other papers based on research carried out in laboratory conditions, using different experimental models and various simulation software [40-43]. Compared to the results obtained in the cited papers, which are based on experimental laboratory models, our research aims to test seed cleaning systems and MOG from real combines, used for harvesting cereals and technical plants. For these reasons, our research is original, and allows testing the performance of cleaning systems from any type of combine.”

For detailed revisions, please refer to lines 345-353 on pages 12-13 of the revised manuscript.

Comments 2: Scope of experimental validation
The experiments were conducted using only a single model of a combine harvester. The absence of a comparison with another model (e.g., from a different manufacturer) limits the generalizability and robustness of the results.

Response 2: Agreed. We appreciate the valuable comments on the substantiation of the purpose and objectives of our research and we specify that we have conducted studies on several brands of combine harvesters, such as New Holland TC 5050, Deutz-Fahr 5660 HTS, Claas Tucano 320, Gloria C14P (under the LAVERDA license), but these results will be the subject of another paper, to be published in the future. To convince you that our results are substantiated, I attach a photo from September 2025, from a stubble field, where you can see the wheat samulastra, resulting from grain losses, which are not uniform across the width of the header due to the unevenness of the air flow. The harvesting was performed with the John Deere T6 combine.   

Comments 3: Boundary conditions and model assumptions
The assumption that the air velocity at the frame boundary equals 0 m/s requires further justification. Does the frame edge adhere perfectly to the channel wall through which the air flows? To strengthen model validation, it is recommended to experimentally introduce a non-zero velocity at the boundary and analyze the model’s behavior under such conditions.

Response 3: We agree with this comment. Thank you, your observation is correct. It is true that local resistances appear in the area of ​​the side walls of the screen housing, due to both friction with the vertical walls, and especially the frames and blinds of the two screens. In order to avoid introducing new obstacles that would produce local resistances, when designing the stand we took into account the following aspects: the width of the side bars of the frame should not exceed the size of the screen frame (see Figure 5 b). Also, from the data analysis it was found that the side ridges, with maximum speeds, are positioned along the screen in the areas 100-300 mm and 600-900mm (Figure 12), as a result the device frame does not influence the results obtained.

We have noted your recommendation and will take it into account in the next tests.

Comments 4: Influence of the measurement frame
The measurement system frame appears to introduce additional airflow disturbances. The authors might consider reducing the number of rods, particularly the edge rods located near the channel wall, to minimize such effects. 

Response 4: Agree. Thank you for your observation. As I mentioned above, when designing the stand, it was taken into account that its constructive elements should not create areas of local resistance that would produce additional disturbances. Also, the sensors were mounted at a distance of 50 mm above the sieve surface to avoid measuring in areas with turbulence created by the sieve shutters. To avoid errors, 10 identical repetitions were made for each variant, the stand being fully automated, and the data were saved directly to a computer.

Also, the RBF model was used for the graphic representation. Radial basis function (RBF) interpolation is an advanced method in approximation theory for constructing high-order accurate interpolants of unstructured data, possibly in high-dimensional spaces.

Comments 5: Asymmetry in airflow velocity
The results indicate a slight difference in air velocity between the two sides of the frame. The cause of this discrepancy should be investigated — whether it is related to the combine’s structural design or to measurement system inaccuracies. It is suggested to swap the sensors to verify whether the difference persists.

Response 5: We agree with your question and thank you for the effort you have made to carefully analyze our work. The distribution of the air flow, in the transverse plane, is uneven, especially in combines equipped with centrifugal-tangential fans, because the air intake is carried out through the side areas and the share of the flow is discharged through these areas. So, in the middle area the air flow velocity decreases significantly. To demonstrate this, we measured the air flow velocity at the end of the fan discharge connection. As a result, the cause of the uneven air flow comes from the fan. In order to mitigate the lateral ridges, we will carry out research through which we will make constructive modifications to the centrifugal-tangential fan. In fact, for this reason, combine manufacturers have replaced the centrifugal-tangential fan with cross-flow fans or axial fans.

Comments 6: The manuscript should also include detailed information on the electric motor model and its parameters used in the measurement system.

Response 6: Agree. Thanks for the suggestion, I have inserted the following clarification into the text

” The stepper motor is of the NEMA 17 type, and the A4988 driver was used for its command and control.”

For details please see page 6, lines 188-189.

 

Response 2: The English is fine and does not require any improvement.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The revised version has potential for publication consideration. However, in Lines 125 -130 need to be revised as this:

Therefore, the objectives of the study were to .................................................................................................

Please, Lines 125 - 130 should be revised during the proofreading stage when the manuscript is accepted.