Pressure Fluctuation Characteristics Analysis of Centrifugal Pump as Turbine in Its Start-Up Process

Round 1

Reviewer 1 Report

The paper presents important findings on the characteristics of pumps as turbines (PAT) during its transient loading from zero. The computer simulation of the pressure distribution and fluctuation in the volute and around the impeller validated by experiment setup may provide useful information for various industries that utilize the PAT.  Unfortunately, the written is not well done and may improvements can be made over the completion of information and formats that would help readers.

The following are some criticisms and suggestions:

1. In the Introduction section, many citations do not provide sufficient conclusion. In line 40, there is no clear conclusion or “take-home” message from citations 5 to 8. This problem is repeated for citations 9 to 13 and 14 and 15. Readers are only informed about studies being presented but no brief results or important findings are discussed. In page 2, same issues appear. Clear conclusion from citations 16 to 24 are not clearly stated. So, please add these information in the Introduction section.
2. In the Research Method section, the description for variables in equations 1, 2, and 3 should follow immediately for easy reading.
3. For equation 5 – what is the time domain used here?
4. For equation 5 – is the head constant? Would it be fluctuated?
5. In the Calculation Method, there are many terms that are specific for the solver Fluent, for example “definite” condition, “sliding mesh”, “Compute_Force_And_Moment function”, etc. that need to be briefly explained.
6. The caption for Figure 1 should state the used in the algorithm
7. In the “Computational Model” please describe better how the impeller motion is represented in the model. What is the approach here?
8. In Line 107, please give reference to the PTC Creo software and ICEM CFD
9. In line 109, what is “y+” ?
10. In Figure 2 – how many elements used here ? Please describe briefly in the caption.
11. In Figure 3 – what do the left and right y axis represent? Which curve uses the let axis and which one uses the right axis ? Please enlarge the fonts here. What does “Grid Strategy” mean? Briefly describe in the caption.
12. In line 120 – what do points 1 to 8 represent ? Why you selected these locations?
13. In Line 126 – what does RNG mean? Please briefly describe and include citation.
14. In Line 127 – What does SIMPLEC mean and do?
15. In the “Experiment Verification” – please describe the philosophy of the experiment. What do you want to accomplish? How? What measurements you do to get that? And so on.
16. Also, in this section – as much as possible, provide references for the equipment used in the experiment
17. Figure 6 – please use arrows to show the flow direction
18. Figure 7 – please indicate using arrows or something which graphs use which y axis. The legends and fonts used in this graph are way too small.
19. Figure 8 (and many figures after this) – use t (s) for the x axis – so the unit is inside a parentheses – use this principle for the y axis as well. Please do this for all figures.
20. Line 170 – The test results are less than 3 mm/s which meets the allowable … - what does this mean? Give reference.
21. Line 179 – the rotating speed of what here? The blades? – I thought the speed is constant?
22. Fonts in figures 11 to 18 are too small
23. The rest are fine.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Dear Authors,

The subject of the work is very interesting. Issue of paper is an analysis of start-up process  of centrifugal pump as turbine.

Major revision:

Generally, the mathematical description is very poor and is not referred to in the following.

Table 1 shows the PAT data. A technical drawing of the PAT should be shown.

Figures 12, 14, 16 and 18 show the FFTs of the pressures. What is the basis for the occurrence of the dominant pressure peak frequencies.

Minor revision:

Line 126. What SIMPLEC means.

Line 171. “The test results are≤3 mm/s …” is correct unit mm/s, if acceleration is measured.

Why the units [m] (Fig. 3) and [kPa] (Fig. 11 or Fig. 12) are shown in the figures.

Overall, I like the work.

Reviewer

Author Response

Please see the attachment.

Author Response File: Author Response.pdf