Effects of Tip Clearance and Impeller Eccentricity on the Aerodynamic Performance of Mixed Flow Fan
Round 1
Reviewer 1 Report
Accepted in present form.
Author Response
Dear Editors:
We gratefully appreciate the editor and all reviewers for their time spend making positive and constructive comments. These comments are all valuable and helpful for revising and improving our manuscript entitled ” Analysis of the Influence of Tip Clearance and Impeller Eccentricity of the Fan on Aerodynamic Performance” (ID: symmetry-2105670), as well as the important guiding significance to our researches.
We have studied comments carefully and have made correction which we hope meet with approval. Revised portions are marked in red in the revised manuscript.
Thank you and best regards.
Yours sincerely,
Yizhe Guo
Reviewer 2 Report
1. The title can be changed to Effects of tip clearance and impeller…
2. Frankly, the impact of tip clearance on the aerodynamic performance of blade is a common sense and such effect is well written in textbooks as well as some literatures (such as Ref 6,7 etc. in the manuscript). The impeller eccentricity also has detrimental effects on the blades. I just wonder what’s the main finding of this paper. If just changes the research object from centrifugal blade to axial fan or mixed-type fan, I can’t support to publish this paper, the authors should state the main difference between this paper and the textbook or literature. Or to explain the mixed type fan will bring some new flow problems when considering tip clearance. The gradient of fan efficiency this seems not a major problem.
3. Table 1 should list the corresponding values of atmosphere pressure and etc.
4. 90deg arc inlet nozzle, this term is confusing, the air flows from left to right in Fig1.b, it should not be called nozzle and 90 degrees is also not suitable. “Inlet” is sufficient.
5. Title of 2.2 should be changed to experimental setup.
6. How to measure the efficiency of the fan from Fig 1? This should be mentioned in the text.
7. In the section 2.3.1, the installation clearance should be non-dimensionalized.
8. What about the measuring error of the efficiency in Fig3
9. As the authors have performed CFD, it should compare the numerical obtained efficiency and the experimental values (Fig 3 -7).
10. A section of introduction of the numerical method as well as validation should be added.
11. The vectors can be replaced by streamlines in Fig 9.
12. Why the turbulent kinetic show a significant circumferential distortion in Fig.15?
13. The English writing should be improved greatly.
14. If the experimental and numerical sections can be collapsed, it will be much better to depicts why the tip clearance has detrimental effects on the fan.
To be summarized, I think such work is worth for publication, the authors should reorganize the whole paper, and make a major revision on the current version.
Author Response
Dear Editors:
We gratefully appreciate the editor and all reviewers for their time spend making positive and constructive comments. These comments are all valuable and helpful for revising and improving our manuscript entitled ” Analysis of the Influence of Tip Clearance and Impeller Eccentricity of the Fan on Aerodynamic Performance” (ID: symmetry-2105670), as well as the important guiding significance to our researches.
We have studied comments carefully and have made correction which we hope meet with approval. Revised portions are marked in red in the revised manuscript. The summary of corrections and the responses to the reviewer’s comments are listed in the Response to Reviewer 2 Comments.
Thank you and best regards.
Yours sincerely,
Yizhe Guo
Author Response File: 
Author Response.docx
Reviewer 3 Report
Dear Authors,
This is a very interesting and valuable manuscript.
The topic fits into the scope of MDPI Symmetry Journal. This is the appropriate place to publish the paper because it can reach a broad audience of readers.
The practical problems of tip clearance and rotor misalignment were investigated. The experimental setup has been shown. Next, CFD simulations were performed. The results have were using high-quality figures. The results have been discussed very carefully. I also think that some other researchers could reproduce the presented results.
The paper is original and clear. The length of the article is appropriate. English language and style are rather fine. I found several small mistakes (please see the attached pdf file).
However, I am of the opinion that some modifications should be introduced.
General concept comments
1. Could you improve state of the art? The research background should include more references. Also, the research gap should be mentioned using one or two sentences. You have cited some works, but it should be rather a critical review of the existing literature.
2. What is the main contribution of this paper when compared to existing literature? A short statement should be included in the introduction. This fact is not obvious at this moment.
3. I observed that sometimes the model is not very accurate. For example, please compare Figure 3a and 7a: the results are not the same. On the other hand, curves on Figure 3 c and 7c are fine. Could you explain these differences between reality and model? It seems that the model is quite “optimistic”.
4. The conclusion is well-written and appropriate but too short. Could you clearly indicate the novelty and importance of the paper? Please include some comments about your CFD model fidelity. I suggest that at the end of the manuscript, you should include a brief description of further possible research directions.
5. You have investigated two main important parameters (tip clearance and rotor misalignment). This is only a partial analysis of the system's performance. If I understand correctly you have assumed that the fan casing is perfectly circular. Are you able to investigate the influence of deformed casing (ellipsoid cross section) on the system operation? If not, please include a short comment in the paper.
6. The organization of the paper must be changed (please see specific comments below). Figures and tables should be placed in proper locations.
7. I suggest publishing the experimental data as supplementary material. In that way, the results might be useful for some other researchers.
Specific comments
Lines 74-74
Table 1 should be placed after the sentence: “The measured results were calculated and processed using the system software for the collected signals, and the parameters to be measured are demonstrated in Table 1.”
Lines 100-104
I think that it will be much better to paste Figure 2 after the sentence, "The eccentricity between the impeller and the housing was changed by adding padded rubber pads between the two split devices above (Figure 2 (b)).”
Lines 121-125
The same issue as earlier: Figure 3 should be placed after “The comparison of total pressure efficiency and static pressure efficiency under different clearances was shown in Figure 3.”
Lines 196-208
Have you tried to investigate the solution accuracy for various grid types and turbulence models? For example, using 6.6, 7.6, and 8.6 million elements. Could you briefly discuss how you determined the number of required grid elements? I think that you can present the computational mesh and some details in separate figures.
Line 416
Citation 5 should be corrected.
Citation 17 is unclear.
The Bibliography should be formatted according to MDPI requirements. It must be pointed out that you have cited papers from the last five years (this is a good practice).
Summary
This paper has significant potential. I will recommend the paper to the publication when the abovementioned issues are solved. I hope that the manuscript can be published in the Symmetry Journal.
I highlighted my comments using yellow color in the attached pdf file.
Kind Regards,
Reviewer
Comments for author File: 
Comments.pdf
Author Response
Dear Editors:
We gratefully appreciate the editor and all reviewers for their time spend making positive and constructive comments. These comments are all valuable and helpful for revising and improving our manuscript entitled ” Analysis of the Influence of Tip Clearance and Impeller Eccentricity of the Fan on Aerodynamic Performance” (ID: symmetry-2105670), as well as the important guiding significance to our researches.
We have studied comments carefully and have made correction which we hope meet with approval. Revised portions are marked in red in the revised manuscript. The summary of corrections and the responses to the reviewer’s comments are listed in the Response to Reviewer 3 Comments.
Thank you and best regards.
Yours sincerely,
Yizhe Guo
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
The authors have modified the some of my concerns. There still remains some of minor problems, as listed below:
1. Title should be "Effects of Tip Clearance and Impeller Eccentricity on the Aerodynamic Performance of mixed flow fan"
2. Caption of Fig 2, number 2 is still nozzle, it is incorrect,please check the whole paper.
3. page 4, line 121, G/T1236 2000 is incorrect.
4. the authors have added a new section of grid independence, this is good. But, the validation of numerical method is needed.
5. A Q-criterion visualization of the tip vortex can be added into the paper.
Author Response
Dear Editors:
We gratefully appreciate the editor and all reviewers for their time spend making positive and constructive comments. These comments are all valuable and helpful for revising and improving our manuscript entitled ” Analysis of the Influence of Tip Clearance and Impeller Eccentricity of the Fan on Aerodynamic Performance” (ID: symmetry-2105670), as well as the important guiding significance to our researches.
We have studied comments carefully and have made correction which we hope meet with approval.
Thank you and best regards.
Yours sincerely,
Yizhe Guo
Author Response File: Author Response.docx
Reviewer 3 Report
Dear Authors.
I appreciate that you responded to all my comments. I think the manuscript might be accepted for publication in the proposed form or after small modifications. Of course, the final layout will be a bit modified by the Editorial Staff. The data collection process was described in detail. Especially thank you for presenting “Table 3”. Some additional conclusions were formulated. However, I have found some minor mistakes (please see the attached pdf file).
Specific comments:
Line 103 (Table 1)
“torque” should be replaced by “Torque” (please use capital letter).
Line 243
“The Realizable k-ε model is selected as the turbulence model[23]…” should be replaced by “The Realizable k-ε model is selected as the turbulence model [23]…” (missing space).
Lines 275 and 297
“Where…” should be changed to “where” (this is the explanation of some symbols).
In my opinion, obtaining a more reliable model is possible, but you explained this issue in the cover letter. I recommend revising the text again to eliminate typographical and language errors and publishing the manuscript.
Kind regards,
Reviewer
Comments for author File: Comments.pdf
Author Response
Dear Editors:
We gratefully appreciate the editor and all reviewers for their time spend making positive and constructive comments. These comments are all valuable and helpful for revising and improving our manuscript entitled ” Analysis of the Influence of Tip Clearance and Impeller Eccentricity of the Fan on Aerodynamic Performance” (ID: symmetry-2105670), as well as the important guiding significance to our researches.
We have studied comments carefully and have made correction which we hope meet with approval.
Thank you and best regards.
Yours sincerely,
Yizhe Guo
Author Response File: Author Response.docx
