Round 1

Reviewer 1 Report

In this study, the authors intend to improve the reflux characteristins of a deep-sea pump and they used CFD and experimental methods as the tools.

The work done is reported in good detail and would be useful to the improvement of the design of the deep-sea pumps.

The manuscript has been written well and the work done is of good quality. The following suggestions/comments need to be addressed before publishing the article.

1. Modify the title. The title can begin with "Design Optimization..." or "Optimizing the design of...". In its current form, the title is linguistically incorrect.

2. Give references to equations 1-7.

3. There are several symbols and subscripts. Include nomenclature with units

4. Rep (Reynolds number) is based on particle diameter, particle velocity or fluid velocity? Needs to be clarified.

5. A detailed schematic diagram indicating all the geometric features mentioned in Table 3 would be useful to the reader.

6. Figure 10 has 6 sub-figures. They need to be labelled as 'a', 'b', etc. for clarity in the discussion that followed.

7. In the Testing section,speeds are mentioned as 1100 rmp, 1200 rmp etc. Is it RPM (rotations per minute)? If not, what does 'rmp' stand for? 'rmp' appears in the conclusions section too.

8. In Table 4, efficiency is mentioned. Efficiency has to be defined in the manuscript.

9. Captions of figures 14 and 15 must be more detailed.

10. References in the conclusions is strange. Try to avoid.

Author Response

Dear Editor and Reviewers,

Thank you for your time and effort in reviewing our manuscript, and thank you so much for giving us an opportunity to revise our manuscript entitled " Optimization design of deep-sea lift pump based on reflux characteristics" (Manuscript ID:1777734). We are grateful for the detailed comments and suggestions provided by each of the reviewers. All of the comments are valuable and very helpful for revising and improving the quality of our paper and the important guiding significance to our follow-up research.

We have considered the comments carefully and have made revisions to address the concerns of each reviewer. The amendments are highlighted in red in the revised manuscript. A point by point response to the reviewers' comments is listed below this letter. We hope the changes listed have made the manuscript suitable for publication, and we look forward to your response.

Once again, thank you so much for your valuable comments and suggestions.

Sincerely,

Li yuanwen

Response to the Reviewers' Comments

(The following part presents point-by-point responses to the two reviewers' comments)

Reviewer #1

Comment 1: Modify the title. The title can begin with "Design Optimization..." or "Optimizing the design of...". In its current form, the title is linguistically incorrect.

Authors' Response: Thank you for your specific comment.

The title has been modified to Design optimization of deep-sea lift pump based on reflux characteristics

Comment 2: Give references to equations 1-7?

Authors' Response:

I have added references,

Hu, Q.; Chen, J.; Deng, L.; Kang, Y.; Liu, S. CFD-DEM simulation of backflow blockage of deep-sea multistage pump. J. Mar. Sci. Eng. 2021, 9(9), 987:1–987:19; DOI:10.3390/jmse9090987.

Comment 3: There are several symbols and subscripts. Include nomenclature with units

Authors' Response:

I have edited the text

Comment 4: Rep (Reynolds number) is based on particle diameter, particle velocity or fluid velocity? Needs to be clarified.

Authors' Response:

The Reynolds number is determined by the velocity of the particle relative to the fluid and the particle diameter.

Comment 5: A detailed schematic diagram indicating all the geometric features mentioned in Table 3 would be useful to the reader.

Authors' Response:

Thank you for your specific and insightful comment,

Figure 4 shows the pump shaft in profile. The colored areas show the main flow path through the pump, which is the computational domain in this study.

Figure 4. Axial section of impeller and diffuser.

The impeller is the main hydraulic work component of the pump. The main parameters of its hydraulic structure are the impeller inlet diameter D_j, minimum outside diameter D₁, inlet installing angle β₁, maximum outside diameter D₂, impeller outlet width b₂, outlet installing angle β₂, and blade wrap angle φ. These are shown in Figure 5.

Figure 5. Main structural parameters of the impeller.

The main hydraulic structure parameters of the space guide vane are the guide vane inlet width b₃, maximum inlet diameter D₃, maximum outside diameter D_4, inlet installing angle α₁, outlet installing angle α₂, and guide vane wrap angle φ₂. These are shown in Figure 6.

Figure 6. Main structural parameters of the guide vane.

Comment 6:Figure 10 has 6 sub-figures. They need to be labelled as 'a', 'b', etc. for clarity in the discussion that followed.

Authors' Response:

I have edited the text

Comment 7: In the Testing section,speeds are mentioned as 1100 rmp, 1200 rmp etc. Is it RPM (rotations per minute)? If not, what does 'rmp' stand for? 'rmp' appears in the conclusions section too.

Authors' Response:

I have modified to rpm

Comment 8: In Table 4, efficiency is mentioned. Efficiency has to be defined in the manuscript.

Authors' Response:

I have added the following:

,                                                    (13)

where ω3 is the rotational speed and M is the impeller torque, both of which can be ob-tained in the post-processing of the numerical simulation.

Comment 9: Captions of figures 14 and 15 must be more detailed.

Authors' Response: I have added the following:

For a rotational speed of 1450 rpm, the head and efficiency of the lifting pump at different flow rates were measured. The test results and numerical simulation results are shown in Figure 18.

Comment 10: References in the conclusions is strange. Try to avoid.

Authors' Response: I have deleted

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

The studies carried out by the authors are certainly relevant and of scientific interest, as they are aimed at increasing the capacity of the deep-sea lift pump, which is in demand in the conditions of mining.

I believe that the authors have conducted detailed and sufficient theoretical and experimental research on this topic, however, several questions and recommendations have appeared:

1) Add information at the end of the Introduction section about the advantages of the proposed studies compared to the rest. What do these developments allow us to achieve that previous studies by other authors could not achieve?

2) In conclusion, it is desirable to add information about the cost and payback assessment of the proposed upgrades to the design of the deep-sea lift pump.

3) Will the model work at other values of volume concentration and maximum particle size? It is desirable to justify the choice of modeling parameters.

4) A note on the design of the text:

-links to formulas should be on the right side.

-in Figure 2 there are fuzzy signatures

Author Response

Dear Editor and Reviewers,

Thank you for your time and effort in reviewing our manuscript, and thank you so much for giving us an opportunity to revise our manuscript entitled " Optimization design of deep-sea lift pump based on reflux characteristics" (Manuscript ID:1777734). We are grateful for the detailed comments and suggestions provided by each of the reviewers. All of the comments are valuable and very helpful for revising and improving the quality of our paper and the important guiding significance to our follow-up research.

We have considered the comments carefully and have made revisions to address the concerns of each reviewer. The amendments are highlighted in red in the revised manuscript. A point by point response to the reviewers' comments is listed below this letter. We hope the changes listed have made the manuscript suitable for publication, and we look forward to your response.

Once again, thank you so much for your valuable comments and suggestions.

Sincerely,

Li yuanwen

Response to the Reviewers' Comments

(The following part presents point-by-point responses to the two reviewers' comments)

Reviewer #1

Comment 1:  Add information at the end of the Introduction section about the advantages of the proposed studies compared to the rest. What do these developments allow us to achieve that previous studies by other authors could not achieve?

Authors' Response: Thank you for your specific comment.

To date, there have been few studies of pump reflux capacity that use numerical simu-lation methods. Thus, this study adopted the CFD–DEM coupling algorithm, considering the particle volume effect and particle collision effect. Numerical simulation was performed to analyze the reflux in a slurry pump, and the reason for reflux blockage of the pump was evaluated. The results provide a theoretical basis for the design of a reflux slurry pump.

Comment 2: In conclusion, it is desirable to add information about the cost and payback assessment of the proposed upgrades to the design of the deep-sea lift pump.

Authors' Response:  I have added in the text. Through this design optimization process, the head and efficiency can meet the design requirements, and the reflux performance is improved over that of the original pump.

Comment 3: Will the model work at other values of volume concentration and maximum particle size? It is desirable to justify the choice of modeling parameters.

Authors' Response:

Thank you for your specific comment.

According to technical requirements，this model is only designed for the working conditions of deep-sea mining, where the particle size is less than 20 mm, and the particle concentration is less thean 6%. The operation of the pump under other working conditions will be studied in future researches.

Comment 4: A note on the design of the text:

-links to formulas should be on the right side.

-in Figure 2 there are fuzzy signatures

Authors' Response: It has been correted.

Figure 2. Axial view of space guide vane of deep-sea mining pump.

Please see the attachment

Author Response File: Author Response.pdf

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.