Effect of Surface Roughness on the Performance of a Shallow Spiral Groove Liquid Mechanical Seal

Round 1

Reviewer 1 Report

The article ‘’ Effect of Surface Roughness on the Performance of a Shallow Spiral Groove Liquid Mechanical Seal’’ presented for the review. The topic is interested, however, there are some major comments for the authors to improve the quality of the paper. Some very important aspects and parameters are missing in the manuscript. Also, the English language and English language structure need to be considered for the improvements. My comments are appended below:

 

1. The article should start with the ‘’why/problem’’ of the study. Authors need to exclusively write the problem statement before explaining the working of the paper, so that the justification of the research work could be identified.
2. Line 13 of the abstract ‘’ The results indicated that’’ authors should add some main findings before straightforward jumping to the this line.
3. Authors should add some parametric values / statistical figured values considered for finding the effect of the roughness of the shallow groove seal.
4. In line 14-15 of the abstract, authors mentioned ‘’ . In different parts of the seal, the improvement in the opening force caused by roughness is not the same.’’ Instead of writing about this straight conclusion, it should be re-write with logical reasoning line that why this is so?
5. Line 17 of the abstract, instead of general discussion in the abstract section, authors should add numeric value for the ‘’ when the rotating speed is high’’. i.e. how much speed is high or what is the limit since the seal is very sensitive with particular value of the speed. So what is high or low value of speed, should be mentioned specifically.
6. Again for line 19, ‘’ The higher the speed, the larger is the positive leakage.’’ Above comment question.
7. Line 21: ‘’ Within the studied speed range’’ what is this speed? This is not a good way of scientific writing in the research papers.
8. Abstract should end with the solution of a problem and/or any application. There is nothing like why this study was important and which problem for a particular and/or general applications this research is useful. It is important so that the readers of this article can get benefit for some particular solutions.
9. Introduction started with very old literature from ‘’1968’’, I think this study is not so novel that we need to include the history of the literature.
10. Authors should have idea that what is appropriate place of mentioning the reference. At some places, authors have given 2-3 references combined and sometime important numeric figure values didn’t include any reference. There should be some uniformity and coherence.
11. In 2^nd para of the introduction, authors mentioned ‘’ Recently, the effect of roughness has frequently been ignored in studies on sealing performance’’, whereas the references are from 2015 and 2018. Authors should carefully look into this, while writing text and mentioning reference.
12. In the next para, authors again mentioned about 1966 literature, whereas in the last para authors talking about ‘’recently’’. This make no sense. Literature of the article should be revised appropriately and thoroughly.
13. Page 2, line 45: Normally, in the scientific writing personal nouns are avoided. Authors are advised to proof read the complete article for the deletion of personal nouns. i.e. ‘’I, we, You, They’’ etc.
14. Again in Line 46, authors used once again very old literature from 1973 and then 1979. These all should be replaced with the latest advancement and proposed solutions related to the article.
15. The complete literature review / introduction section need to be updated and this should be addressed seriously. Authors should consider the latest papers related to the topic from the processes journal of MDPI to match the readership.
16. The last para of the introduction in a research paper is very important and critical, which is totally missing here. Please include the relevant information as per the research papers standards.
17. In the section 2, ‘’ 2. Geometric and Mathematic Model’’ the authors have used extensive literature. Please note that the general equations and information related to the geometric models should be used in the introduction section unless it is very necessary.
18. The figure 3 caption is not understandable ‘’ Boundary conditions of the lubricating film calculation domain’’ The figure mention something different.
19. The axes values of figure 4 to 7 are not-readable. The authors should improve the quality of the figures for better understanding.
20. There are only 24 references in the article. Many of them are very old. Authors MUST revise the introduction section and add some more relevant literature.

Author Response

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Reviewer 2 Report

The paper is verry interesting and in certain way may contribute to the journal. 

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Reviewer 3 Report

The paper describes a simulation model that was used to investigate the effect of surface roughness on the performance of a shallow spiral groove mechanical seal, as well as the relationships between surface roughness, friction torque, and positive/negative leakage. I propose that the paper be published after the following revisions:

1. In the introduction, it would be beneficial to the reader to include further details regarding the background of mechanical face seals.
2. It would be nice to describe "sealing performance" more clearly in the introduction, as it is mentioned several times.
3. Most parameters in eqs. 3, 4, and 5 are not defined (e.g., v_mi), please clearly define all the parameters.
4. The reason for the skewed shape of the rough micro-element in Fig. 2 is ambiguous. Can you show how the element relates to the spiral groove with another illustration?
5. Can you confirm that the middle arrow pointing to the rotational wall in fig. 3 is correct? It appears to be pointing to the side wall rather than the upper surface.
6. Line 170: What is the number of dividing lines N? Please clearly define it.
7. Can you provide an illustration of the mesh you used? What is the relationship between resolution and groove size? How did you ensure that the resolution is fine enough near grooves? The discussion in section 2.3 does not make this clear.
8. In section 2.3, use dimensionless numbers to describe the mesh independence metrics (e.g., grid size vs groove size). It is not appropriate to use grid numbers without context (for example, on line 181: 1576243).
9. The logic in section 2.3 is difficult to follow; please explain the rationale and metrics used for grid independence validation first, then show the results.
10. How is the friction power dissipation calculated?
11. Can you describe the system and represent the results using dimensionless numbers? As a result, the presented results would be more generalizable and useful as a reference.
12. Because oil is a non-Newtonian fluid (and its value varies significantly depending on temperature or shear), I expect it to have a significant impact on the results presented here. Could you explain why a constant viscosity is used instead?

Author Response

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Reviewer 4 Report

The manuscript deals with a computational study of the effect of surface roughness on the sealing performance of a shallow spiral mechanical seal using a mixture model. The simulation of this process is quite complex and requires vast knowledge about the physics and computational aspects. Moreover, the numerical results are of interest since it considers the effect of roughness in different locations of the numerical domain. The manuscript deserves to be published, but certain minor issues should be considered before:

1. Why did the authors not consider the effect of thermal dissipation in their model? It is known that under high shear rates, oils may present this phenomenon.
2. Justify the use of the Zwart–Gerber–Belamri cavitation model.
3. If the flow is laminar, why is important to consider the effect of roughness? 
4. The authors mention several numerical parameters but they do not mention the implemented software. 
5. Please, improve the quality of the figures, increasing the font size.
6. The authors should describe the physical situation of the experimental set-up used for validation.
7. Why the numerical results obtained by the authors are so different from those numerically obtained in [24]?

 

Author Response

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Round 2

Reviewer 1 Report

Authors have addressed many comments, however, still there is improvement suggested in presenting the results logically with technical reasons. 

One main concern is still there that references are less in number. Also, there are many references from 1992, 2008, 2013. Authors are advised to add literature not older than 3-4 years, unless a very conceptual content from old literature, which might not be available in the recent past.  Authors are suggested to add some relevant references from the same journal so that it can enhance the relevancy with this journal and for better readership.

 

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Reviewer 3 Report

I suggest publication of the paper after the following minor revisions:

Point 4: "The reason for the skewed shape of the rough micro-element in Fig. 2 is ambiguous. Can you show how the element relates to the spiral groove with another illustration?"

Re: The author has not explained how the skewed element shown relates to the spiral groove; instead, they have simply increased the image's resolution. Please explain how the element is defined, either with an illustration or in-text, as it is not clear (in terms of explanation).

• The symbol N is used for multiple parameters (e.g., dividing lines, friction power dissipation, etc).
• The viscosity is assumed to be constant in Section 2.2, but the author's rebuttal mentions that they ignored the effect of viscosity. If this is the case, please correct assumption 4.

 

Author Response

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