Improving the Efficiency of the Drive of the Test Bench of Rotary Hydraulic Machines

Round 1

Reviewer 1 Report

Some suggestions are as follows.

1. It is suggested to strengthen the description of references.

2. It is suggested to further enhance the readability of the paper's expression.

3. It is suggested to further provide methods for improving system performance.

4. It is suggested to further clarify the innovation of the paper.

Author Response

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

Comments 1: It is suggested to strengthen the description of references

Response 1: The description of the links to the sources has been updated. Corrections are highlighted in color in the section Introduction. Thank you for pointing this out. We agree with this comment.

Comments 2: It is suggested to further enhance the readability of the paper's expression.

Response 2: Changes have been made to the text. Thank you for pointing this out. We agree with this comment.

Comments 4: It is suggested to further clarify the innovation of the paper.

Response 4: We have, changed Conclusions.to emphasize this point. . Corrections are highlighted in color in the section

Reviewer 2 Report

The paper is about an interesting topic but I report relevant suggestions.

The introduction must be improved. It is not possible to present the literature citing 14 papers in one sentence, line 59. And also line 80 could be improved 15-20.

Line 106 107

This sentence is wrong:  ”The increase in pressure in the pressure line is due to the fact that the supply of  working fluid by the hydraulic pump is slightly greater than that consumed by the  hydraulic motor.” The pressure increases because it is necessary to move the motor rotating part, depending on the torque applied to the motor.

The fluid entering in the pipe connecting pump and motor is equal to the fluid exiting to the pipe, only at the beginning there is the effect of the oil compressibility but once the pressure has reached the steady state value the oil entering and exiting is equal, otherwise the oil pressure will continue to increase.

WHAT eq. 3 is? The pressure evolution should be calculated using the filling emptying equation, that is the mass conservation equation and the state equation of the fluid based on the bulk modulus.

What live section is? Line 164 reports:

“…the area of the live section of thecorresponding hydraulic resistance…”

Line 136

There aren’t  the cited papers 21-24, the list reference stops at 20!

Figure 2

It is hard to understand why do you study a pipe with internal orifice and not the hydraulic machines with their efficiencies. Please explain the meaning.

In figure 3 and figure 4 and others there are not the axis titles.

Nothing in y axis. In x axis t,s must be written as time [s]

Line 203

Please check what you write If Ned becomes zero the efficiency coefficient is equal to infinity not to 1.

Line 231

“…respectively the make–up pump… “       what is the make-up pump ?

Why in figure 12 the symbols are different respect to figure 5. HM ? P? etc.

In Figure 6 what is AD? But also what are NP MP ? Why have the reader to guess ?

Add a nomenclature

Figure 5 must be improved, labels are over symbols.

This the conclusion “It is established that the main design parameters affecting the increase in the energy  efficiency of the hydromechanical drive system of the stand include: the gear ratio of the mechanical transmission, the rotation frequency of the electric motor, the pressure setting  of the safety valve, the working volume of the hydraulic motor and hydraulic pump”

I am wondering why there are not a figures where the efficiency coefficient is reported as a function of the cited parameters.

This paper never cites the efficiencies of the hydraulic machines, Volumetric, hydromechanical and total efficiency (reported in table 1 at nominal rate) , these values depend on the operative conditions of the machines, neglect this aspect in a test bench focusing on efficiency issue is hard to understand.

Author Response

Response to Reviewer 2 Comments

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

Comments 1: The introduction must be improved.

Response 1: The description of the links to the sources has been updated. Corrections are highlighted in color in the section Introduction. Thank you for pointing this out. We agree with this comment.

Comments 2: WHAT eq. 3 is?

Response 2:  The explanation is highlighted in color in the article on page 4 of equation 3.

Comments 3: It is hard to understand why do you study a pipe with internal orifice and not the hydraulic machines with their efficiencies.

Response 3: Figure 2 is used to explain equation 3. In the elementary section, the influence of the properties of the working fluid on the instantaneous reduced coefficient of volumetric stiffness of the selected section of the hydraulic system is explained

Comments 4: Please check what you write If Ned becomes zero the efficiency coefficient is equal to infinity not to 1.

Response 4: One of the features of the testing process of technical systems, including hydraulic machines, is that there is no generalized criterion for evaluating the efficiency of the testing process.

The efficiency coefficient, in its classical formulation, cannot be accepted as an assessment of the cost-effectiveness of the test process, since there is no "useful power" during testing, the usefulness of testing lies in obtaining the test results themselves, and therefore it is necessary to expend (lose) energy for testing.

In this paper, as a criterion for evaluating the efficiency of the testing process, it is proposed to use the "test energy efficiency coefficient" equal to the ratio of the power passing through the tested hydraulic machines during their testing to the power spent on testing.

The formula of the "test energy efficiency coefficient" has the form:

where N_ED is the power supplied to the electric motor during testing, N_ISP is the load power of the hydraulic machines being tested.

To ensure a high level of efficiency of the test process, it is necessary to create conditions under which the energy efficiency coefficient of the test will significantly exceed 1, which will indicate that the power consumed during the test process is significantly less than the power required to conduct tests with proper load.

The explanation is highlighted in color in the article on page 6-7 of equation 12.

Comments 5:  I am wondering why there are not a figures where the efficiency coefficient is reported as a function of the cited parameters.

Response 5: We have, changed Conclusions.to emphasize this point. . Corrections are highlighted in color in the section

Comments 6:  This paper never cites the efficiencies of the hydraulic machines, Volumetric, hydromechanical and total efficiency (reported in table 1 at nominal rate) , these values depend on the operative conditions of the machines, neglect this aspect in a test bench focusing on efficiency issue is hard to understand.

Response 6: During the operation of the test bench, the pressure in the system varies widely, which forces the modeling and calculations to take into account the change in the volumetric efficiency coefficient nvol.akt of hydraulic machines, which is determined by the formula

where nvol.nom is the nominal value of the volumetric efficiency of a hydraulic machine, which is assumed to be equal to the volumetric efficiency of a hydraulic machine operating at nominal pressure; pnom is the nominal value of the working pressure of a hydraulic machine; pact is the actual value of the working pressure.

The explanation is highlighted in color in the article on page 8 of equation 13.

Author Response File: Author Response.pdf

Reviewer 3 Report

Ensure the correct usage of the decimal separator.

The authors are advised to exclude specific Russian characters from the text, particularly on lines 117, 1189, 129, 130, etc.

In Figure 2, maintain consistency in units: prefer 16 MPa and 10.2 MPa over 10200 Pa.

For Figures 3 and 4, incorporate variables and units for both the x and y axes.

In Table 1, eliminate all instances of ";" and "."

The authors are required to furnish a lucid explanation that establishes a clear connection between theoretical and experimental data, including an error analysis.

The authors are advised to exclude specific Russian characters from the text, particularly on lines 117, 1189, 129, 130, etc.

Author Response

Thank you very much for taking the time to review this manuscript. Please review the corrections highlighted in the section "Track changes to resubmitted files".

Round 2

Reviewer 2 Report

The paper has been improved following the suggestions. 

Author Response

Thank you very much for taking the time to review this manuscript.

Reviewer 3 Report

In addressing the challenge of mitigating motion disturbance in the electro-hydraulic servo loading system and effectively reducing the impact of uncertainties on system performance, the authors propose an innovative approach. This involves implementing a specialized control system dedicated to regulating pressure in the load port. However, the current text is hindered by cross-reference errors, which impede a clear understanding. Therefore, I recommend submitting a revised version for improved clarity.

NA

Author Response

Thank you very much for taking the time to review this manuscript. The quality of the translation of the text of the article has been improved.

Round 3

Reviewer 3 Report

The authors have diligently incorporated the requested changes as per the feedback. Consequently, I confidently recommend the publication of the manuscript.

NA.