Experimental Analysis of the Effect of Wear Factors on Guide Vane of Hydraulic Turbine

Round 1

Reviewer 1 Report

The paper offers the experimental and numerical results of the effect of wear factors on guide vane of hydraulic turbine.

The kind of research is interesting, but the reviewer would like to comment some problems:

• The manuscript should describe how their work can affect sustainability and efficiency improvement. In my opinion, the introduction should be expanded to describe sustainability aspects and the implications for increasing efficiency.
• In Conclusion, the design implications and limitations are not clearly presented. The authors should explain what kind of limitations their methodology has.

Line 11. Capital letters?

Line 38/63/64/71. References format

Table I grit or Sand?. In my opinion, it is more appropriate Sand.

Therefore, I am of the opinion that the article can be accepted in the present form after minor revision.

Author Response

Point 1: The manuscript should describe how their work can affect sustainability and efficiency improvement. In my opinion, the introduction should be expanded to describe sustainability aspects and the implications for increasing efficiency.

Response 1: I thank the reviewers for their valuable comments and in response to this issue, I have added an explanation of the operational efficiency and sustainability of the power plant unit from this test at the end of the introduction, as follows.

The experimental study provides guidance to the power station on the problem of wear of the internal parts of the turbine by sediment, a theoretical basis for the selection of spraying materials and polishing over the parts, and the need for the power station to pay attention to the influence of river acidity on the wear of the parts. Through the above considered wear factors, the overall operating efficiency of the turbine unit of the power station can be improved, providing a guarantee for the sustainability of the power station.

Point 2: In Conclusion, the design implications and limitations are not clearly presented. The authors should explain what kind of limitations their methodology has.

Response 2: I thank the reviewers for their valuable comments. I have noted the deficiencies regarding this trial in the conclusion of the article, and the trials we are doing now will help to reduce such errors and deficiencies, so the suggestions you gave are valuable. The specific explanation is as follows.

The design of this paper helps to analyze and study the influence of the guide vane under different working conditions by the sediment wear factor, but considering that the internal flow of the turbine is more complicated, a real model can be considered for the study if the fund is sufficient, in addition about the experimental measurement error cannot be neglected. In the next research, we are committed to the real model test and further reduce the test error by more times of measurement method.

Point 3: Capital letters?

Response 3: Thank you for the advice given by the reviewer, it was my mistake and I have corrected the capitalization issue.

Point 4: Line 38/63/64/71. References format

Response 4: Thanks to the advice given by the reviewers, I have corrected the problem.

Point 5: Table I grit or Sand?. In my opinion, it is more appropriate Sand.

Response 5: Thank you for the suggestions given by the reviewer, I have corrected them as you requested.

Reviewer 2 Report

The present paper “Experimental analysis of the effect of wear factors on guide vane of hydraulic turbine” deals with , a test bench built according to the actual internal flow of the hydraulic turbine of a power station.

This is an interesting topic, but some appreciations are made by this reviewer.

Abstract, This is adequate, resuming the main objectives and achievements of the present document. Nevertheless, in this reviewer opinion, the novelty and technical interest of this research would be welcome in this section, in order to aim readers to continue the reading of the text and to consider interest for other future actions.

There are no Keywords in the version received by this reviewer.

1. This section is well presented, depicting an analysis of the state of the art in the question of modelling wear factors in vanes of hydraulic machinery. Here authors present novelties but in this reviewer opinion, also objectives would be welcome in this section.
2. Test bench design and Prototype processing
   2.1. Test bench design. This section is well presented, with many details over the modelling questions. Some questions arise with the figures. Which sense have the colors in Figure 4?
   • Prototype processing. This is also a descriptive section, and it is detailed and interesting. In this reviewer opinion, Figures 8 and 9 are too similar. It would be interesting to see more description of the differences before and after the grinding. Figure 12 is also not very clear as the differences between simulations and real model can not be clearly contrasted.
3. . Analysis of test results

This is an interesting results section, but in this reviewer opinion, differences in Figure 15 an d 16 are also very subtle. Would it be possible to quantify these differences in any sort of indicator?. In general, these results are interesting and well documented.

4. Estimated life of guide vane

 This is a results section, According to the authors, the increment of life in the guide vane can be estimated. Is this proportional increase applicable to different cases?

5. Conclusions

This section presents a set of conclusions related to the previous analysis. In this reviewer opinion it would be interesting to see the degree of accomplishment of the objectives, the novelty of the results and the possible application of the present technique to other systems or cases in order to extrapolate the present research.

Author Response

Point 1: There are no Keywords in the version received by this reviewer.

Response 1: I would like to thank the reviewers for their valuable comments, and I sincerely apologize for not seeing the keywords I added, probably because of me. Here are my keywords for this article.

Keywords: guide vane, wear, Tungsten Carbide, pH, Roughness

Point 2: This section is well presented, depicting an analysis of the state of the art in the question of modelling wear factors in vanes of hydraulic machinery. Here authors present novelties but in this reviewer opinion, also objectives would be welcome in this section.

Response 2: First of all, I would like to express my sincere gratitude to the reviewers for their appreciation and I will continue to do my best. In addition, I added at the end of the introduction that the objective of this test is to provide guidance on the wear of the guide vane of the power station, so that the power station personnel can analyze the specific service life of the guide vane based on our test and provide a basis for power station maintenance, and also give different treatment options to increase the service life of the guide vane, as follows.

The experimental study provides guidance to the power station on the problem of wear of the internal parts of the turbine by sediment, a theoretical basis for the selection of spraying materials and polishing over the parts, and the need for the power station to pay attention to the influence of river acidity on the wear of the parts. Through the above considered wear factors, the overall operating efficiency of the turbine unit of the power station can be improved, providing a guarantee for the sustainability of the power station.

Point 3: Test bench design. This section is well presented, with many details over the modelling questions. Some questions arise with the figures. Which sense have the colors in Figure 4?

Prototype processing. This is also a descriptive section, and it is detailed and interesting. In this reviewer opinion, Figures 8 and 9 are too similar. It would be interesting to see more description of the differences before and after the grinding. Figure 12 is also not very clear as the differences between simulations and real model can not be clearly contrasted.

Response 3: First of all, I would like to thank the reviewers for their valuable comments. Figure 4 shows the velocity distribution of the fixed guide vane and guide vane in the full flow channel of the turbine, because this article is an experimental study, so the simulation study can only be used as a reference. Regarding the problem of Figure 8 and Figure 9, it may be due to my improper expression. This is actually a polishing and grinding to reduce the surface roughness of the guide vane, because it is indeed difficult to distinguish with the naked eye, so I added the roughness picture after the 3D morphometer test. Regarding the problem of Figure 12, because of the limitation of simulation technology, we cannot control the change of working condition during the calculation, so the simulation calculation result is the wear condition of a single working condition, while the turbine operation of the power station will have several working conditions, but the serious parts of wear given in the calculation working condition are reflected in the physical picture we took, so I personally think this should be appropriate.

Point 4: This is an interesting results section, but in this reviewer opinion, differences in Figure 15 an d 16 are also very subtle. Would it be possible to quantify these differences in any sort of indicator?. In general, these results are interesting and well documented.

Response 4: First of all, I would like to thank the reviewers for their valuable comments, and thank you for your appreciation of my article. Regarding the comments you gave, I think it is difficult for us to solve the problem because we obtained the wear data by measuring the surface of the specimen after the test, which is a specific expression of the test results. Regarding the application of indicators to quantify this difference, we will find out the variation pattern of the wear amount and give a specific expression in the next experimental study. Again, I thank the reviewers for their comments, and I apologize for not being able to fully address this issue.

Point 5: This is a results section, According to the authors, the increment of life in the guide vane can be estimated. Is this proportional increase applicable to different cases?

Response 5: First of all, I would like to thank the reviewers for their valuable comments. Regarding this issue, the wear of the guide vane depends to a large extent on the sand content of the river where the power station is located, and this test is proportioned according to the sand content of the power station for many years. The article gives the life usage under two operating conditions, so this paper is based on the life prediction of the guide vane according to the wear of the power station under these two operating conditions. Once again, we thank the reviewers for their valuable comments.

Point 6: This section presents a set of conclusions related to the previous analysis. In this reviewer opinion it would be interesting to see the degree of accomplishment of the objectives, the novelty of the results and the possible application of the present technique to other systems or cases in order to extrapolate the present research.

Response 6: First of all, I thank the reviewers for their valuable comments on this issue, and I explain the significance of this experiment at the end of the conclusion and give the deficiencies as follows.

The design of this paper helps to analyze and study the influence of the guide vane under different working conditions by the sediment wear factor, but considering that the internal flow of the turbine is more complicated, a real model can be considered for the study if the fund is sufficient, in addition about the experimental measurement error cannot be neglected. In the next research, we are committed to the real model test and further reduce the test error by more times of measurement method.

Reviewer 3 Report

The following comments need to be addressed by authors:

1. Justify the reason for selection of tungsten carbide coating although many coating materials are available.
2. What is the coating thickness used and hardness of coatings need to be explained.
3. Have you tested any corrosion studies, if so kindly provide details. Please note that material undergoes corrosion with parts working in fluid environment.
4. Highlight all parts name correspond to all figure.
5. Improve the resolutions of all figures.
6. There is no significant difference in results of surface of guide vanes (refer to Fig. 15 and 16).
7. Highlight white and grey patches in figures.
8. Thermal spray parameters need to be reported with a focus on how those values are selected and set in a machine.
9. It is not clear, how the life of guide vanes are determined.

Author Response

Point 1: Justify the reason for selection of tungsten carbide coating although many coating materials are available. What is the coating thickness used and hardness of coatings need to be explained.

Response 1: Thank you for the comments given by the reviewer, for this issue I have added the advantages of using tungsten carbide coating and provided the thickness of tungsten carbide coating for this test is 0.3mm hardness HV=1264. as follows.

Tungsten carbide coating is highly dense, with high bonding strength, porosity can be less than 1%, bonding strength can be more than 70 Mpa. low oxidation of the coating material, less carbon loss, high hardness of the coating. High-speed impact and strong deformation distort the lattice of the material and increase the activity of the material, thus increasing the possibility of physical bonding with adjacent particles or substrate materials, which makes the coating highly reliable.

Point 2: Have you tested any corrosion studies, if so kindly provide details. Please note that material undergoes corrosion with parts working in fluid environment.

Response 2: Thanks to the valuable comments made by the reviewer, the corrosion study conducted in this test is based on the PH value of the water body where the power station is located, the average PH value of the water body of the power station is 6.73, because the pH value of water is 4 to 9, the corrosion of steel mainly depends on the concentration of oxygen, with the increase in oxygen concentration, the flow rate of water increases, the diffusion rate of oxygen reaching the metal surface increases, the stagnant liquid layer on the metal surface also becomes thinner, oxygen consumption Corrosion rate is accelerated. The oxygen content of the water changes with the temperature, so we simulate the average water temperature in the dry and flood periods of the power station to carry out the test. Considering that the maximum objective magnification of the 3D morphometer we used is 50 times, so a higher magnification is needed to take into account the oxygen consumption corrosion of the guide vane surface, so we measured the relationship between the change of wear amount at these two temperatures to study the oxygen consumption corrosion. We intend to analyze the oxygen-consuming corrosion of the guide vane surface in detail with the help of higher-level equipment given by other institutions in our next experiments. Once again, we thank the reviewers for their valuable suggestions.

Point 3: Highlight all parts name correspond to all figure.

Response 3: I thank the reviewers for their valuable comments, and I have revised accordingly to your meaning.

Point 4: Improve the resolutions of all figures.

Response 4: Thank you for the valuable comments from the reviewers, I have modified the images accordingly according to your meaning, but some images (e.g. Figure 7, Figure 15, Figure 16) were produced by the corresponding instruments, I have tried my best to adjust them as clear as possible, I hope you can understand.

Point 5: There is no significant difference in results of surface of guide vanes (refer to Fig. 15 and 16).

Response 5: First of all, I would like to thank the reviewers for their valuable comments. Figure 15 and Figure 16 show the surface morphology of the guide vane under high magnification objective, and my explanation for these figures is to let the readers guide that the wear at the head of the guide vane (that is, near the engraving point 29) is mainly in the form of sediment particle impact wear, and the wear at the tail of the guide vane (that is, near the engraving points 1 and 2) is in the form of scouring wear, as can be seen. The wear is more serious at P=42.8MW, which may not be visible at the tail position, because we took the surface morphology picture, and the wear amount is depicted in Figure 13. The change of wear at the head position can be seen clearly. At P=42.8MW, there are many large pits on the surface morphology of the guide vane, while at P=30.9MW, the pits are relatively small, which confirms our conjecture is correct. Once again, we thank the reviewers for their valuable comments.

Point 6: Highlight white and grey patches in figures.

Response 6: I would like to thank the reviewers for their valuable comments, and I am willing to make changes as you intended, but I may be rather obtuse, so could you please suggest me exactly which images I need to change. Thank you again for your valuable comments and I sincerely apologize to you for my stupidity.

Point 7: Thermal spray parameters need to be reported with a focus on how those values are selected and set in a machine.

Response 7: First of all, I would like to thank the reviewers for their valuable comments, and I am sorry for this problem. Since our organization does not have tungsten carbide coating equipment, we invited other organizations to do the tungsten carbide coating process, and our requirement is to spray 0.3mm thickness of tungsten carbide coating and the hardness should be above 1200. I asked the organization if they could give us specific values, but the answer was negative. All they can give us is the hardness value and the physical properties of the tungsten carbide used. Again, I apologize, but I have added the physical properties of the tungsten carbide used in this test to the article in tabular form.

Point 8: It is not clear, how the life of guide vanes are determined.

Response 8: First of all, I would like to thank the reviewers for their valuable comments and I apologize to you for not expressing myself clearly. I would like to explain to you in detail about the estimated life of the guide vane. First of all, we find the sum of the wear at each point of the guide vane on the front and back side according to the test, and find the maximum wear, which can be obtained in Figure 22-24. Secondly, we divide the maximum wear amount by the total time of the test operation to get the wear rate under this condition, of course, the wear test under different water temperature corresponds to the wear condition of the power station in the flood and dry water period. Finally, the maximum wear depth of the guide vane does not exceed 8 mm (this is explained in the article and cited in the corresponding article) to obtain the service life of the guide vane.

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.