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by
  • Ziming Kou 1,2,*,
  • Lin Zhang 1 and
  • Buwen Zhang 1

Reviewer 1: Anonymous Reviewer 2: Anonymous

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

1. Overall comments

 

The manuscript designed a two-speed buffer valve to improve the transition dynamics of the hydraulic support pushing system under high pressure, flow, and water-based medium for coal mining. Two channels are machined on the valve spool to connect the inlet and outlet ports to reduce the pressure peaks at the opening and closing of the electro-hydraulic reversing valve. The pressure and flow characteristics were studied by CFD and experimental tests. It was concluded that the designed two-buffered valve can improve the pressure distribution and the cavitation from CFD results and can reduce the steady-state error of the position tracking from experimental results. The manuscript introduced an extra component instead of modifying the electro-hydraulic reversing valve as in the existing literature. The language and writing quality needed to be improved and some revisions are required before the manuscript can be published. Please see the specific comments below.

 

 

 

2. Specific comments

 

1) In line 33-48, the improvement of previous work was not quantified, for example, what and how has been improved by their work? It would be easy to compare with the work presented in this manuscript if the authors could present some quantitative values.

2) In line 49-59, the authors did not identify the research gap accurately. What is the disadvantage of optimising/modifying the electro-hydraulic reversing valve? Why did the authors decide to design an extra two-speed buffer valve instead of optimising the electro-hydraulic reversing valve? Some explanation of the motivation needs to be added.

3) In line 63, it mentioned the theoretical analysis of the pushing system is conducted. However, there was no theoretical modelling found anywhere in the manuscript. Please consider deleting this sentence or adding the theoretical part and comparing it with the experimental results.

4) In line 73, did the authors mean “ … always connect the liquid inlet and outlet”? Please clarify and correct it.

5) In Table 1 of CFD modelling, the water is used as the medium. Does it mean that the hydraulic support pushing system uses water instead of hydraulic oil as the working fluid?

6) In Figure 4(a) and (b), the subfigure captions were wrong. (a) should be “without throttling runner”and (b) should be “with throttling runner”. Please correct this.

7) In Figure 7, the flow rate or speed versus time can be added to show the speed change because of the opening and closing of the buffer valve.

8) The buffer valve enables the pushing system to start and stop at a low speed to reduce pressure peaks. However, this makes the system slower as in Figure 10(a) and (b). It is about 1-2 s slower with the buffer valve. In addition, the buffer valve adds more resistance to the hydraulic line, which throttles the flow and dissipates much more energy. The authors may add some discussion on the disadvantages caused by the designed buffer valve.

9) The word “mutation” used in the manuscript is strange and difficult to understand. The authors may consider changing it to “sudden change”.

10) The texts in all figures are difficult to read. Please use clearer and bigger fonts and update all figures.

11) There are typos on punctuation marks and grammar mistakes. The manuscript needs some editing for language and writing quality.

Comments on the Quality of English Language

There are typos on punctuation marks and grammar mistakes. The manuscript needs some editing for language and writing quality.

Author Response

  • In line 33-48, the improvement of previous work was not quantified, for example, what and how has been improved by their work? It would be easy to compare with the work presented in this manuscript if the authors could present some quantitative values.

 

This part has been adjusted in the revised paper.

 

  • In line 49-59, the authors did not identify the research gap accurately. What is the disadvantage of optimising/modifying the electro-hydraulic reversing valve? Why did the authors decide to design an extra two-speed buffer valve instead of optimising the electro-hydraulic reversing valve? Some explanation of the motivation needs to be added.

 

As for the explanation of motivation, I have explained it in my revised paper. Here is a brief explanation : because the underground hydraulic support system uses a near-water medium, under this working condition, some existing high-performance proportional servo valves are rarely used ( proportional servo valves generally use gap seals, oil can be sealed, and water seals will leak ). Although some schemes of using proportional private service valves to transform electric directional valves are studied in many studies, they are rarely used in industry. Therefore, this cartridge cone valve ( using a two-speed buffer valve, placed in front of the electro-hydraulic directional valve can directly control the rear liquid supply mode ) is used.

 

 

  • In line 63, it mentioned the theoretical analysis of the pushing system is conducted. However, there was no theoretical modelling found anywhere in the manuscript. Please consider deleting this sentence or adding the theoretical part and comparing it with the experimental results.

 

I have supplemented the part of the theoretical model of the passage system in the revised paper.

 

  • In line 73, did the authors mean “ … always connect the liquid inlet and outlet”? Please clarify and correct it.

 

This part has been adjusted in the revised paper.

 

  • In Table 1 of CFD modelling, the water is used as the medium. Does it mean that the hydraulic support pushing system uses water instead of hydraulic oil as the working fluid?

 

Because the downhole system is mainly used in the emulsion and water to form a transmission medium, the emulsion accounts for about 5 %, basically the same as the nature of the water. So the simulation approximates water.

 

  • In Figure 4(a) and (b), the subfigure captions were wrong. (a) should be “without throttling runner”and (b) should be “with throttling runner”. Please correct this.

 

This part has been adjusted in the revised paper.

 

  • In Figure 7, the flow rate or speed versus time can be added to show the speed change because of the opening and closing of the buffer valve.

 

Because in the experiment, because the sensor used to study the pressure characteristics is the displacement sensor when the line is drawn, it is impossible to measure the speed. At the beginning, there is no high pressure flowmeter, only the pressure characteristics. For the velocity flow characteristics, only some experiments with large flow rate and small flow rate were carried out. Due to the influence of the experimental platform and the environment, this part cannot be tested.

 

 

  • The buffer valve enables the pushing system to start and stop at a low speed to reduce pressure peaks. However, this makes the system slower as in Figure 10(a) and (b). It is about 1-2 s slower with the buffer valve. In addition, the buffer valve adds more resistance to the hydraulic line, which throttles the flow and dissipates much more energy. The authors may add some discussion on the disadvantages caused by the designed buffer valve.

 

Although its time slowed down, but because in practice its actual impact process is very short, can be ignored. In practice, greatly convenient positioning, and then the positioning accuracy has been greatly improved, the hydraulic impact is also reduced a lot.

 

  • The word “mutation” used in the manuscript is strange and difficult to understand. The authors may consider changing it to “sudden change”.

 

This part has been adjusted in the revised paper.

 

  • The texts in all figures are difficult to read. Please use clearer and bigger fonts and update all figures.

 

This part has been adjusted in the revised paper.

 

  • There are typos on punctuation marks and grammar mistakes. The manuscript needs some editing for language and writing quality.

 

This part has been adjusted in the revised paper.

 

 

Reviewer 2 Report

Comments and Suggestions for Authors

1. It would be good to talk about the control strategy used to obtain these graphs.

2. Citations should not go as a super index.

3. Improve the introduction

4. Improve the quality of the text in Figure 2.

5. Improve the quality of the text in Figure 3

6. The hydraulic diagram should be placed separately, because it is of very poor quality.

7. There are many spelling mistakes, please correct them

8. The figures must have a hyperlink which takes you to the referenced figure.

9. In figures 7-10. Change time/s to time [sec]. In the same way for the “y” axis, displacement/mm per displacement [mm].

10. Improve conclusions

11. Improve bibliographic references

Comments on the Quality of English Language

No comment

Author Response

  1. It would be good to talk about the control strategy used to obtain these graphs.

 

The charts in this paper are obtained from experiments and consulting a large number of relevant materials. The charts in this paper are based on theoretical analysis and related models, by considering the corresponding working conditions, and then do a lot of experiments and analysis.

 

  1. Citations should not go as a super index.

 

This part has been adjusted in the revised paper.

 

  1. Improve the introduction

 

This part has been adjusted in the revised paper.

 

  1. Improve the quality of the text in Figure 2.

 

This part has been adjusted in the revised paper.

 

  1. Improve the quality of the text in Figure 3

 

This part has been adjusted in the revised paper.

 

  1. The hydraulic diagram should be placed separately, because it is of very poor quality.

 

This part has been adjusted in the revised paper.

 

  1. There are many spelling mistakes, please correct them

 

This part has been adjusted in the revised paper.

 

  1. The figures must have a hyperlink which takes you to the referenced figure.

 

This part has been adjusted in the revised paper.

 

  1. In figures 7-10. Change time/s to time [sec]. In the same way for the “y” axis, displacement/mm per displacement [mm].

 

This part has been adjusted in the revised paper.

 

  1. Improve conclusions

 

This part has been adjusted in the revised paper.

 

  1. Improve bibliographic references

 

This part has been adjusted in the revised paper.

 

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Add more bibliographical references to the work

Comments on the Quality of English Language

No comment

Author Response

1:Add more bibliographical references to the work

  This part has been adjusted in the revised paper.