Research on Multi-Objective Optimization of Low Pulsation Unloading Damping Groove of Axial Piston Pump

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

1. Abstract: lines 16 and 17 are separated

2. Figures: Figures 1, 4, 6, 7 and 8 have not been mentioned in the text

3. In figures 3, 4 and 5, use "()" to simplify the definition of units. Example Angle (deg).

4. in figure 8 Use "()" for consistency

5. The table display cannot be separated, for example table 1.

6. Inconsistent table writing, see tables 1 and 2.

 

Comments for author File: Comments.pdf

Author Response

Comments 1: Abstract: lines 16 and 17 are separated.
Response 1: Thanks to the careful review of the reviewer, some of the content of the article has been revised
Comments 2: Figures: Figures 1, 4, 6, 7 and 8 have not been mentioned in the text. 
Response 2: Thanks to the careful review of the reviewer, the error stated has been corrected
Comments 3: In figures 3, 4 and 5, use "()" to simplify the definition of units. Example Angle (deg).
Response 3: Thanks for the reviewer's comments, it has been revised
Comments 4: in figure 8 Use "()" for consistency
Response 4: Thanks for the reviewer's comments, it has been revised
Comments 5: The table display cannot be separated, for example table 1.
Response 5: Thanks for the reviewer's comments, it has been revised
Comments 6: Inconsistent table writing, see tables 1 and 2.
Response 6: Thanks for the reviewer's comments, it has been revised

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors,

Please refer the attachment for the detailed review comments.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

The quality of English is acceptable but it requires a minor editing. 

 

Author Response

Comments 1: The different levels adopted for the structural optimization of buffer tank must be mentioned in the abstract itself.
Response 1: The abstract of the paper has been revised
Comments 2: Why the letter ‘A’ has been capitalized in many places in the word “Angle”, although it appears in the middle of the sentences. 
Response 2: Thanks to the careful review of the reviewer, the above issues have been modified
Comments 3: The literature review section is very weak. Rather than telling what is done by whom, it must throw some light on the importance of this work and what is really missing in the literature. This section requires a complete revision.
Response 3: The literature review part of the paper has been rewritten
Comments 4: The importance / novelty of this work should be highlighted at the end of Introduction section. Now, it is missing.
Response 4: The novelty of the paper is supplemented in the first section
Comments 5: The parameter units in the equation are given after their symbols.
Response 5: Thanks for the reviewer's comments, it has been revised
Comments 6: Page No.3, Line No.97, the figure number is not mentioned. It will lead to confusion to the readers. Correct this error in the revision.
Response 6: The figure number is 1, which has been supplemented and explained in the original text.
Comments 7: It is wonder to see that there are two equations with same equation number (2).  (Page No.3, Line No. 101)
Response 7: Renumber all formulas in the original text.
Comments 8: The parameters mentioned in Eqn.(2) to Eqn. (8) are not defined. Without definition, it would be very difficult to understand what Rf is, Ɵ. etc are referring to.
Response 8: The modifications have been made in the text, and all parameter symbols have been defined.
Comments 9: What is SCDM? It is nowhere mentioned in the manuscript.
Response 9: The full name "Space Claim Direct Modeler" is a pre-processing modeling software that can quickly extract the internal flow field of a piston pump. This study used this software to complete the pre-processing of the internal flow field of the piston pump.
Comments 10: In figure 3 & 4, X axis is represented as angle. What the angle the authors are intended to refer. That is not mentioned in the main text.
Response 10: The angle represents the rotation angle of the cylinder block. In this study, the piston pump has 9 pistons. When the pump rotates one cycle, it experiences 9 periodic flow pulsations with the same variation pattern, with a 40° gap between each cycle. In order to better extract the detailed characteristics of flow pulsation changes, a single pulsation cycle was selected for analysis, that is, the flow variation when the cylinder block rotates over 40°.
Comments 11: The authors should explain the logic behind the selection of range for parameters mentioned in Table 3
Response 11: Relevant content has been added in the article. [In this paper, NSGA-II algorithm is used for multi-objective optimization of damping groove structure parameters. For the NSGA-II algorithm, a larger population size provides a wider search space, so for this example, the population size is set to 100. Through multiple calculations, it is found that when the number of iterations is greater than 100, the example converges, so the number of iterations is set to 100. The efficiency of cross-pairing and the efficiency of mutation operations are used for optimization fine-tuning, which is set to 20 in this example. In addition, a higher crossover probability helps to explore new regions of the solution space, while a higher mutation probability helps to maintain population diversity, so the crossover probability is set to 0.9 and the mutation probability is set to 0.1 in this example.]
Comments 12: Future research directions can be added in the conclusion section.
Response 12: The outlook section has been supplemented

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The study focuses on optimizing the valve plate structure of an axial piston pump to minimize pressure shocks and flow fluctuations. It examines the effect of a triangular buffer groove on the outlet pressure and flow characteristics. Theoretical analysis and CFD simulations are used to understand these effects. A multi-objective optimization algorithm is then applied to enhance the buffer groove's design, significantly reducing pressure and flow pulsations at the pump outlet. The authors need to address some issues.

1.     The percentage of similarity in this manuscript is quite high. Please make efforts to reduce it by paraphrasing more effectively and ensuring originality in your writing.

2.     The formatting of the text is inconsistent. Please ensure that the text adheres to the journal’s formatting guidelines. (Lines 16-17)

3.     There is no Equation (9) provided, and Equation (10) appears to be misnumbered. Please review and correct the equation numbering.

4.     The novelty of the research is not clearly stated.

5.     I recommend adding a concluding paragraph at the end of the introduction to provide a roadmap for the readers.

6.     Elaborate on the CFD method used, including the mesh generation, boundary conditions, and any assumptions made.

7.     How does the triangular groove structure affect the outlet pressure and flow characteristics of the axial piston pump?

8.     Can the authors provide a more detailed explanation of the CFD method used in the study?

 

9.     The conclusion is not well-written. Revise the conclusion to include a summary of the main findings of your study.

Comments on the Quality of English Language

There are some minior grammatical errors. 

Author Response

Comments 1: The percentage of similarity in this manuscript is quite high. Please make efforts to reduce it by paraphrasing more effectively and ensuring originality in your writing.
Response 1: Thanks to the careful review of the reviewer, some of the content of the article has been revised
Comments 2: The formatting of the text is inconsistent. Please ensure that the text adheres to the journal’s formatting guidelines. (Lines 16-17).
Response 2: Thanks to the careful review of the reviewer, the error stated has been corrected
Comments 3: There is no Equation (9) provided, and Equation (10) appears to be misnumbered. Please review and correct the equation numbering.
Response 3: Renumber all formulas in the original text.
Comments 4: The novelty of the research is not clearly stated.
Response 4: Thanks to the careful review of the reviewer, the paper has been added to the innovation. [This study focuses on the low pulsation optimization design of piston pumps, with the buffer groove structure installed on the distribution plate as the research object. By using computational fluid dynamics methods, the flow characteristics and variation patterns of pumps under multiple different structural parameters are solved. A multi-objective intelligent optimization algorithm is proposed for the structural optimization of buffer slots to enhance the adaptive optimization calculation of buffer slots. Research has shown that optimization algorithms can greatly improve the efficiency of damping groove optimization, and the optimization effect has been verified through simulation technology. The multi-objective optimization method proposed by this research institute can provide a certain reference for the optimization design of the buffer groove of the distribution plate.]
Comments 5: I recommend adding a concluding paragraph at the end of the introduction to provide a roadmap for the readers.
Response 5: Thanks to the careful review of the reviewer, the technical route of the paper has been supplemented. [In this study, a multi-objective based intelligent optimization algorithm is proposed to enhance the adaptive optimization computation of the buffer tank. The purpose of optimizing the buffer tank is to reduce the flow pulsation and pressure shock of the piston pump. Therefore, the content of this study mainly contains the following aspects, the theoretical model of the buffer tank flow is established in Section 2, and the structural characteristic parameters characterizing the buffer tank are defined, the simulation model of the internal flow field of the whole pump of the piston pump is established in Sections 3 and 4, and numerical calculations are carried out for the pressure and flow characteristics of the piston pump, and then, based on the simulation results, the influences of the buffer tank width angle, depth angle, and the length on the dynamic characteristics of the pump are analyzed. Finally, the optimal solution of the buffer tank structure is obtained by the multi-objective genetic optimization algorithm and verified by the simulation method. Conclusions are drawn in Section 5.]
Comments 6: Elaborate on the CFD method used, including the mesh generation, boundary conditions, and any assumptions made.
Response 6: The computational fluid dynamics method used in this study discretizes the fluid calculation domain of the piston pump, and then uses control equations to solve the physical quantities of each discrete element. Numerical calculations are completed by dividing the watershed grid, setting boundary conditions, and controlling the solution parameters.(line191-194)
Comments 7: Elaborate on the CFD method used, including the mesh generation, boundary conditions, and any assumptions made.
Response 7: The computational fluid dynamics method used in this study discretizes the fluid calculation domain of the piston pump, and then uses control equations to solve the physical quantities of each discrete element. Numerical calculations are completed by dividing the watershed grid, setting boundary conditions, and controlling the solution parameters.(line222-226)
Grid generation:
1) Import and export watershed: This watershed is a stationary watershed, with a streamlined surface and no too severe bending mutations. Therefore, when dividing the grid, the number of grids can be appropriately reduced. Grid generation is achieved through the universal grid partitioning technique provided by CFD software, and corresponding grid control parameters are set: maximum grid size, minimum grid size, and face grid size.
2) Distribution plate watershed: This watershed is a stationary watershed, with fine structures of pre boost buffer tanks and pre release buffer tanks distributed on the distribution surface. Therefore, when dividing the grid, it is necessary to increase the number of grids. This is to better calculate the fluid flow state of the top window of the cylinder block plug hole after passing through the buffer tank, making the calculation results more accurate. Grid generation is carried out through the universal grid partitioning technique provided by CFD software, and corresponding grid control parameters are set: maximum grid size, minimum grid size, and face grid size, and the control parameters need to be appropriately reduced.
3) Distribution sub oil film watershed: This watershed is a stationary watershed that plays a crucial role in lubrication and leakage control of the distribution sub. Due to its radial thickness reaching the micrometer level, the number of grids needs to be appropriately increased during grid division. Using finite element preprocessing tools, divide the mesh here, set the radial thickness to 20 μ m, and evenly divide it into 4 layers.
4) Piston rotor basin: This basin is a motion basin, and the motion form of the rotor is composite motion, that is, reciprocating linear motion in the cylinder block plug hole and rotating motion with the cylinder block. For the motion grid, each time step is calculated to reconstruct and deform the watershed boundary according to the laws of motion. Therefore, when dividing the grid, the piston rotor grid template included in CFD software is selected. By setting the piston rotor parameters: number of pistons, rotation center, rotation axis, and grid control parameters (the same as the general grid template), the grid fully satisfies the motion form of the piston rotor during the working process. (line226-254)
Boundary conditions: The boundary conditions of computational fluid dynamics are necessary conditions for limiting the computational fluid domain and obtaining the target results through numerical simulation. For the boundary conditions in this study, pressure boundary conditions are used for both inlet and outlet, with pressure inlet (0.35MPa) and pressure outlet (25MPa) set respectively; Considering the leakage of the oil film in the clearance of the distribution pair, the outer edge of the oil film is set as the pressure outlet (0.5MPa). In addition, except for the pressure boundary, all other boundaries are uniformly set as the solid wall surface, and the rotation speed of the piston pump is set to 1000rpm. (line255-263)
Assumption: The inlet and outlet basins of the piston pump are laminar flow, the outlet basins are low Reynolds number turbulence, the pre pressure boosting and pre pressure relief buffer slots of the distribution plate are high Reynolds number turbulence, and the rotor piston chamber is high Reynolds number turbulence. (line264-268)
Comments 8: How does the triangular groove structure affect the outlet pressure and flow characteristics of the axial piston pump?
Response 8: Thanks for the careful review of the reviewer, the relevant content has been added in the paper. [As a damping structure, the triangular groove plays a throttling role in the working process of the piston pump, especially when the damping groove and the piston chamber are connected, the throttling effect is more obvious. This will affect the normal flow of oil, thereby affecting the size and pulsation of the outlet flow rate of the piston pump.
For triangular grooves, their characteristic parameters are generally divided into width angle, depth angle, and length:
1. For the width angle, when the width angle is small, the overcurrent area is also relatively small, which leads to a greater damping effect of the groove. Therefore, the resistance of flow backflow increases, the amount of backflow decreases, and thus causes significant pressure shocks. When the width angle is large, the flow area gradually increases, the damping effect decreases, and thus the pressure impact is reduced. When the width angle increases to a specific value, the flow rate and pressure impact reach their minimum, and at this point, the time for the pressure to reach steady state remains basically unchanged. When the width angle continues to increase, the flow area becomes too large, and the damping effect of the groove is greatly weakened, leading to severe flow backflow. Therefore, the time for pressure to reach steady state is significantly shortened, but the pressure impact is significantly increased.
2. For the depth angle, it mainly affects the jet angle of the oil flowing out of the groove and the outlet pressure of the front section of the waist shaped groove for oil discharge. When the triangular groove at the front end of the piston chamber and the oil discharge waist groove is connected, the greater the depth angle, the faster the hydraulic recoil speed of the high-pressure oil, resulting in a change in outlet pressure. When the depth angle is a specific value, the pressure overshoot during oil discharge is the lowest, and the flow pulsation at the oil suction and discharge ports is the smallest. But when the depth angle is too small or too large, the pressure overshoot during oil suction and discharge will significantly increase.
3. In terms of length, when determining the width angle and depth angle of the triangular groove, the change in length has little effect on the speed and direction of oil flowing through the triangular groove, but has a significant impact on the outlet pressure of the front section of the oil discharge waist groove.]
Comments 9: Can the authors provide a more detailed explanation of the CFD method used in the study?
Response 9: Relevant content has been added in the paper.
Comments 10: The conclusion is not well-written. Revise the conclusion to include a summary of the main findings of your study.
Response 11: The conclusions of the paper have been revised. [This study focuses on the optimization design of buffer tanks. By using computational fluid dynamics simulation methods, numerical simulations were conducted on multiple different combinations of buffer tank structures, and a detailed analysis was conducted on the strong coupling relationship between the structural parameters of buffer tanks and the pressure flow characteristics of pistonr pumps. Then, a multi-objective intelligent optimization algorithm was proposed to adaptively optimize the buffer tank and obtain the optimal buffer tank configuration. The conclusion is as follows:
1. Simulate and compare the individual characteristic parameters of the buffer tank. For the width angle of the buffer tank, when selecting a width angle of 70 °, the amplitude of flow pulsation is the smallest, with a pulsation rate of 11.82%. For the depth angle of the buffer tank, when the depth angle is 8 °, the flow pulsation amplitude of the pump is the smallest. For the length of the buffer tank, when the length is 23mm, the flow pulsation amplitude of the pump is the smallest.
2. By using multi-objective optimization algorithms to optimize the configuration of the distribution plate buffer groove, the optimized width angle of the buffer groove is 82.3 ° and the depth angle is 12.7 °. The comparison of pressure flow characteristics with the original structure shows that the optimized structure has a flow pulsation rate of 13.7%, which is 0.5% lower than before optimization (flow pulsation rate of 14.2%); The pressure fluctuation is 0.3%, which is 0.1% lower than before optimization (0.4%), and the fluctuation amplitude is 20.09 MPa.]

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have addressed all the comments. Therefore, I suggest the manuscript for publishing in the Journal of  Processes. 

Comments on the Quality of English Language

There are some minor grammatical errors.