Effect of Tip Clearance on Helico-Axial Flow Pump Performance at Off-Design Case
Round 1
Reviewer 1 Report
Review Report
This paper reports numerical results for a pump. The effect of the tip clearance gap on the performance and the flow behavior is considered.
The subject is of interest in the field of flow pumps. The topic and the methodology are not new. Additionally, the paper does add any novel contribution to the targeted research community. Further, the manuscript needs some enhancements regarding English. Accordingly, journal publication is not recommended. The are several issues in the manuscript as listed below:
Major comments
- The literature review needs to be significantly improved, considering also more recent papers. Several recent publications discussed very similar observations concerning the influence of the tip clearance gap on single and two-phase flows. The present work needs to be related to the prior work, highlighting the “new” contribution.
- Why did the authors use the “standard” k-epsilon model? There are many other better alternatives for pump simulations.
- No grid dependence test is given.
- Concerning the numerical method, several details are missing. Is a steady or transient solver considered? How many inner iterations? How many seconds were considered for the physical time of the simulations? For the numerical mesh, what is the wall Y+ value? What is the mesh quality?
- The case of a 0 mm tip clearance gap might be impossible in practical cases. What is the importance of this case?
- The validation shown in Figure 4 is done based on a qualitative way, which makes the comparison very weak. A quantitative comparison should be added.
- Are the results shown in the paper only for single-phase flow? If yes, the word multiphase is misleading.
- The location of the data in Figure 7 is unclear. A graphical representation for the radial coefficient r* and location of the data is need.
- What is the importance of the information shown in Figures 9, 10, and 11?
- The behavior of the data in many figures is just described without giving a real illustration of the physical reasons behind the behavior. This makes the discussions of the paper very poor.
Minor comments
- The specific type of the multiphase flow is not mentioned in the abstract.
- The color bar is missing in Figure 6, which makes the discussion in Section 4.3 meaningless.
- The zoomed views in Figure 13 are almost of the same size as the ones with zooming, adding nothing to the Figure.
- No nomenclatures are given
Author Response
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Author Response File: 
Author Response.docx
Reviewer 2 Report
The paper needs major ligvistic corrections.
Introduction should contain more detailled explanation about novelty of results presented in this paper.
Description of fluid parameters should be added to the section 3. Also information about number of elements, wall functions used and y+ are missing.
Section 3.3 Experimental validation should be more detailled and show that the simulation model describes reality with acceptable accurancy, i.e. do not compare only the flowfield but also other results if possible.
In Section 4, word pressure is used and it is not clear if static (probably) or total pressure is considered. Pressure scale is missing in figure 6.
Conclusion section should contain summary of the paper, not only the conlusion points. Current conclusion section is more like discussion section.
Author Response
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Author Response File: Author Response.docx
Reviewer 3 Report
This paper investigate the effect of tip clearance on helico axial flow pump performance, the topic is interesting but the manuscript needs significant improvement before acceptance for publication:
1. Please illustrate the TLV in the first appearance of TLV in the abstract part;
2. In the first paragraph, the author mentioned the multiphase transportation technology. This concept is very board. What is the multiphase transportation technology in detail?
This concept is not mentioned elsewhere in the manuscript;
3. In the literature review, you mention many scholars employ k-omega SST turbulence model to simulate the flow in the pump, why you choose k-epsilon turbulence model?
Could you please specify it in detail?
4. The introduction part is too short, the importance about the effect of tip clearance has not been fully investigated;
5. For the physical model of the helico axial flow pump, what is the basis of the design? Why you design such a pump?
6. For the mesh arrangement, the mesh distribution at the inlet pipe, impeller, diffuser and outlet pipe should be illustrated in detail;
7. For the numerical simulation, please specify the governing equations and turbulence model in detail;
8. For the comparision between the CFD and experimental flow fields as shown in Figure 5, the author say the TLV in the experiment is in good agreement with CFD result;
Could the author quantitatively analyze the difference between the two result? And how good it is?
9. Experiment part should be placed before the numerical simulation part. For the experimental part, the parameters of the experimental main component should be listed in a Table,
and the uncertainty analysis should be conducted;
10.For the nomenclature part, there are two TSV, please distinguish between these two statements to avoid confusion.
Author Response
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Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
Again, the introduction needs to be improved. Many recent studies, which discuss very similar and important observations concerning the influence of the tip clearance gap on single and two-phase flows, are unfortunately not included.
Author Response
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Author Response File: Author Response.docx
Reviewer 3 Report
The paper is probably publishable, but should be reviewed again un revised form before it is accepted. There are some points that the author doesn't respond to reviewer's comments in the revised manuscript:
1. For the mesh arrangement, the mesh distribution at the inlet pipe, impeller, diffuser and outlet pipe should be illustrated in detail;
2. For the comparision between the CFD and experimental flow fields as shown in Figure 5, the author say the TLV in the experiment is in good agreement with CFD result;
Could the author quantitatively analyze the difference between the two result? And how good it is?
3. Uncertainty analysis should be conducted;
Author Response
Please see the attachment
Author Response File: Author Response.docx
