Abstract

Purpose High power and speed are new demands for rotating machinery which needs the journal bearings with high dynamic characteristics. The critical speed of the rotor-bearing system is one of the most significant parameters to evaluate the dynamic characteristics. This paper aims to investigate the theoretical and experimental analysis of a rotor system supported by large diameter elliptical bearings. Design/methodology/approach To obtain the theoretical and experimental support for rotor-bearing system design, dynamic characteristics theoretical analysis based on the finite difference method is given and an experiment focuses on critical speed identification is carried out. Findings The theoretical calculation results indicate that the critical speed is near to 800 rpm and there is no large vibration amplitude round working speed (1,500 rpm). Using the test bench in the factory unit, vibration data including three experimental processes are obtained. According to the vibration data, the critical speed is identified which also indicates that it is stable when working at 1,500 rpm. Originality/value The design method for the rotor system supported by large diameter elliptical bearing can be obtained by the theoretical and experimental results shown in this paper. Peer review The peer review history for this article is available at:


Authors

Zhao, Zhiming;  Zhang, Rui;  Ji, Feng;  Yuan, Xiaoyang

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  • 1 reviewer
  • pre-publication peer review (FINAL ROUND)
    Decision Letter
    2020/08/08

    08-Aug-2020

    Dear Zhao, Zhiming; Zhang, Rui; Ji, Feng; Yuan, Xiaoyang

    It is a pleasure to accept your manuscript ilt-04-2020-0122.R2, entitled "Theoretical and Experimental Dynamics Analysis of Rotor-bearing System Supported by Elliptical Bearings" in its current form for publication in Industrial Lubrication and Tribology. Please note, no further changes can be made to your manuscript.

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    Editor, Industrial Lubrication and Tribology
    carsten.gachot@tuwien.ac.at

    Decision letter by
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    Reviewer report
    2020/08/08

    In the present work, Stiffness and damping coefficients of hydrodynamic elliptical bearings are determined through numerical analysis and further applied in rotor dynamics. In addition, experimental measurement of FRF related to rotor-bearing system were obtained. Then, stiffness and damping of the elliptical bearings were extracted from the measured FRF. Numerical results are compared with experimental result.
    Authors have addressed the queries in the revised manuscript. The flow chart shown (Flow chart for dynamic coefficients identification) in the response to the reviewers queries section may be included in the manuscript.
    Reviewer is thankful to the authors for implementing the suggestions. The paper may be accepted for the publication.

    Reviewed by
    Cite this review
    Author Response
    2020/08/07

    Dear Editor:
    Thank you very much for your attention and the reviewers’ evaluation and comments on our paper. We revised the manuscript (ilt-04-2020-0122.R1) according to your kind advices and reviewer’ detailed suggestions, and carefully proof-read the manuscript to minimize typographical, grammatical, and bibliographical errors. A revised manuscript with the correction sections marked was attached as the supplemental material and for easy check/editing purpose. We sincerely hope this manuscript will be finally acceptable to be published on Industrial Lubrication and Tribology. Should you have any questions, please contact us without hesitate.

    Best Regards,

    Zhi-ming Zhao

    Here below is our description on revision according to the reviewer’ comments.
    Response to Reviewer 1#
    Date: Aug 12, 2020
    Thank you very much for your constructive comments on our manuscript entitled “Theoretical and Experimental Dynamics Analysis of Rotor bearing System Supported by Elliptical Bearings” submitted to INDUSTRIAL LUBRICATION AND TRIBOLOGY. We have studied these comments carefully and have made corrections and explanations which we hope meet with approval. Revised portion are marked yellow in the revised manuscript which is attached in the end of this file. With regard to your comments, we wish to reply as follows:

    Comment 1: Page 5, line 23 to 30: explanation provided for the Figure 4: It is reported that “as the L/D increase the stiffness coefficients of direction y decrease which might cause the responses of rotor increase”. However, variation in the stiffness would affect the critical speed. Probably, damping values may have the influence on the amplitude of response. Author’s should give a thought over it.
    Response:
    Thank you for your helpful suggestions. We agree with your opinion mentioned in the comment. As a spring damping system the stiffness variation can affect the critical speed, and the damping values have influence on the amplitude of response, especially at the critical speed. However, when the working speed is not near to critical speed, the influence on response amplitude resulted by stiffness value is greater than that by damping value due to the huge difference in quantity levels between stiffness value and the damping value. From Fig.2(a) and Fig.3(a), the conclusion can be drawn that the stiffness values of y direction change obviously with the L/D values. But the stiffness values of y direction and the damping values of both x and y direction change very little with the L/D values. So in our opinion, the main reason resulting in the increase of rotor response amplitude is the stiffness coefficients decrease of direction y decrease due to the L/D increase.
    So the explanation has been revised to “as the L/D value increase the stiffness coefficients of direction y decrease, which might be the main reason resulted in the increase of rotor responses amplitude”, which is marked yellow in the manuscript.
    Comment 2: Figure 5 is referred as Campbell diagram. Captions of Fig. 5 may reframed accordingly.
    Response:
    Thank you for your helpful advices. The captions of Fig.5 has been changed to “Campbell diagrams of rotor bearing system”, and the explanation of Fig.5 has also been revised. The Revised section is marked yellow in the manuscript.
    Comment 3: Details about the calculation procedure of unbalance response (Figure 4) should be provided. Equation of motion should be included. Probably, rotor may have been assumed to be rigid. Details about the rotor system (as follows) should be provided: Total mass of the rotor, distance between the support bearings, unbalance mass.
    Response:
    Thank you for your helpful suggestions. The detail has been added to the manuscript marked yellow as follows:
    The calculation procedures for the unbalance response of the rotor bearing system include: 1) Establish the rotor system model by the finite element method; 2) Establish the oil film force database which can provide the oil film force corresponding to the shaft position at a certain speed; 3) Solve the dynamic differential equations, which can be written as Mz ̈+Cz ̇+Kz=F_bearing+F_unbalance. In this equation, M, C and K are the mass matrix, the external damping matrix and stiffness matrix of rotor, F_bearing is the oil film force of bearings and F_unbalance is the unbalance force which is the function of rotor speed and unbalance mass. The Total mass of the rotor is about 230T supported by two bearings. The distance between the support bearings is about 13m. The unbalance mass added to rotor is about 2.16Kg.mm.
    Comment 4: Detail description of the procedure of identification of stiffness and damping of bearings from frequency response function should be included.
    Response:
    Thank you for your helpful suggestions. the detail of identification method can be found in the authors’ paper as follows: Zhao, Z. M., Ji, F., Guan, Y. S., et al. (2019) “Vibration and critical characteristics of the tilting pads journal bearing-rotor system”, Industrial Lubrication and Tribology, Vol.71 No.2, pp. 295-300. It can be found in the references list in the manuscript.
    The identification method named non-excitation identification is based on multi-speed of rotor system in working field. The method includes three parts as follows. The details processes are as following. 1) According to the experiment data, the vibrations changing with rotation speeds can be obtained; 2) According to theoretical analysis, we assume the stiffness and damping coefficients changing with rotation speeds following quadratic function; 3) Based on the vibration data, sufficient equations can be achieved; 4) solving the equations, and the stiffness and damping coefficients can be got.
    Comment 5: There are grammatical mistakes in the manuscript. Few of them are indicated below: Page 2, line 27: “ techonique”; Page 5, line 50 and 52: sentence beginning with “And”. Author’s should read the manuscript carefully and remove all such grammatical mistakes.
    Response:
    We are very sorry for these language mistakes. The above mentioned mistakes have been revised in the manuscript accordingly. And we have tried our best to check the manuscript thoroughly to avoid the similar mistakes.



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  • pre-publication peer review (ROUND 2)
    Decision Letter
    2020/08/06

    06-Aug-2020

    Dear Dr. Zhao:

    Manuscript ID ilt-04-2020-0122.R1 entitled "Theoretical and Experimental Dynamics Analysis of Rotor-bearing System Supported by Elliptical Bearings" which you submitted to the Industrial Lubrication and Tribology, has been reviewed. The comments of the reviewer(s) are included at the bottom of this letter.

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    Prof. Carsten Gachot
    Editor, Industrial Lubrication and Tribology
    carsten.gachot@tuwien.ac.at

    Reviewer(s)' Comments to Author:
    Reviewer: 1

    Comments to the Author
    In the present work, Stiffness and damping coefficients of hydrodynamic elliptical bearings are determined through numerical analysis and further applied in rotor dynamics. In addition, experimental measurement of FRF related to rotor-bearing system were obtained. Then, stiffness and damping of the elliptical bearings were extracted from the measured FRF. Numerical results are compared with experimental result.
    Authors have addressed most of the queries in the revised manuscript. However, there are some queries which have to be addressed :

    1. Page 5, line 23 to 30: explanation provided for the Figure 4: It is reported that “as the L/D increase the stiffness coefficients of direction y decrease which might cause the responses of rotor increase”
      However, variation in the stiffness would affect the critical speed. Probably, damping values may have the influence on the amplitude of response. Author’s should give a thought over it.
    2. Figure 5 is referred as Campbell diagram. Captions of Fig. 5 may reframed accordingly.
    3. Details about the calculation procedure of unbalance response (Figure 4) should be provided.
      Equation of motion should be included. Probably, rotor may have been assumed to be rigid. Details about the rotor system (as follows) should be provided: Total mass of the rotor, distance between the support bearings, unbalance mass.
    4. Detail description of the procedure of identification of stiffness and damping of bearings from frequency response function should be included.
    5. There are grammatical mistakes in the manuscript. Few of them are indicated below:
      Page 2, line 27: “ techonique”
      Page 5, line 50 and 52: sentence beginning with “And”
      Author’s should read the manuscript carefully and remove all such grammatical mistakes.
      Reviewer: 1

    Recommendation: Minor Revision

    Comments:
    In the present work, Stiffness and damping coefficients of hydrodynamic elliptical bearings are determined through numerical analysis and further applied in rotor dynamics. In addition, experimental measurement of FRF related to rotor-bearing system were obtained. Then, stiffness and damping of the elliptical bearings were extracted from the measured FRF. Numerical results are compared with experimental result.
    Authors have addressed most of the queries in the revised manuscript. However, there are some queries which have to be addressed :

    1. Page 5, line 23 to 30: explanation provided for the Figure 4: It is reported that “as the L/D increase the stiffness coefficients of direction y decrease which might cause the responses of rotor increase”
      However, variation in the stiffness would affect the critical speed. Probably, damping values may have the influence on the amplitude of response. Author’s should give a thought over it.
    2. Figure 5 is referred as Campbell diagram. Captions of Fig. 5 may reframed accordingly.
    3. Details about the calculation procedure of unbalance response (Figure 4) should be provided.
      Equation of motion should be included. Probably, rotor may have been assumed to be rigid. Details about the rotor system (as follows) should be provided: Total mass of the rotor, distance between the support bearings, unbalance mass.
    4. Detail description of the procedure of identification of stiffness and damping of bearings from frequency response function should be included.
    5. There are grammatical mistakes in the manuscript. Few of them are indicated below:
      Page 2, line 27: “ techonique”
      Page 5, line 50 and 52: sentence beginning with “And”
      Author’s should read the manuscript carefully and remove all such grammatical mistakes.

    Additional Questions:
    Originality: Does the paper contain new and significant information adequate to justify publication?: In the present work, Stiffness and damping coefficients of hydrodynamic elliptical bearings are determined through numerical analysis and further applied in rotor dynamics. In addition, experimental measurement of FRF related to rotor-bearing system were obtained. Then, stiffness and damping of the elliptical bearings were extracted from the measured FRF. Numerical results are compared with experimental result. The reviewer agrees that authors have addressed an important aspect from bearing design and its influence on rotor dynamics.

    Relationship to Literature: Does the paper demonstrate an adequate understanding of the relevant literature in the field and cite an appropriate range of literature sources? Is any signficant work ignored?: yes

    Methodology: Is the paper's argument built on an appropriate base of theory, concepts, or other ideas? Has the research or equivalent intellectual work on which the paper is based been well designed? Are the methods employed appropriate?: yes. few comments are provided in the attached file

    Results: Are results presented clearly and analysed appropriately? Do the conclusions adequately tie together the other elements of the paper?: few comments are provided in the attached file

    Practicality and/or Research implications: Does the paper identify clearly any implications for practice and/or further research? Are these implications consistent withthe findings and conclusions of the paper?: yes

    Quality of Communication: Does the paper clearly express its case, measured against the technical language of the field and the expected knowledge of the journal's readership? Has attention been paid to the clarity of expression and readability, such as sentence structure, jargon use, acronyms, etc.: few comments are provided in the attached file

    Reproducible Research: If appropriate, is sufficient information, potentially including data and software, provided to reproduce the results and are the corresponding datasets formally cited?: few comments are provided in the attached file

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    Decision letter by
    Cite this decision letter
    Reviewer report
    2020/08/06

    In the present work, Stiffness and damping coefficients of hydrodynamic elliptical bearings are determined through numerical analysis and further applied in rotor dynamics. In addition, experimental measurement of FRF related to rotor-bearing system were obtained. Then, stiffness and damping of the elliptical bearings were extracted from the measured FRF. Numerical results are compared with experimental result.
    Authors have addressed most of the queries in the revised manuscript. However, there are some queries which have to be addressed :

    1. Page 5, line 23 to 30: explanation provided for the Figure 4: It is reported that “as the L/D increase the stiffness coefficients of direction y decrease which might cause the responses of rotor increase”
      However, variation in the stiffness would affect the critical speed. Probably, damping values may have the influence on the amplitude of response. Author’s should give a thought over it.
    2. Figure 5 is referred as Campbell diagram. Captions of Fig. 5 may reframed accordingly.
    3. Details about the calculation procedure of unbalance response (Figure 4) should be provided.
      Equation of motion should be included. Probably, rotor may have been assumed to be rigid. Details about the rotor system (as follows) should be provided: Total mass of the rotor, distance between the support bearings, unbalance mass.
    4. Detail description of the procedure of identification of stiffness and damping of bearings from frequency response function should be included.
    5. There are grammatical mistakes in the manuscript. Few of them are indicated below:
      Page 2, line 27: “ techonique”
      Page 5, line 50 and 52: sentence beginning with “And”
      Author’s should read the manuscript carefully and remove all such grammatical mistakes.

    Reviewed by
    Cite this review
    Author Response
    2020/07/12

    Dear Editor:
    Thank you very much for your attention and the reviewers’ evaluation and comments on our paper. We revised the manuscript (ilt-04-2020-0122) according to your kind advices and reviewers’ detailed suggestions, and carefully proof-read the manuscript to minimize typographical, grammatical, and bibliographical errors. A revised manuscript with the correction sections marked was attached as the supplemental material and for easy check/editing purpose. We sincerely hope this manuscript will be finally acceptable to be published on Industrial Lubrication and Tribology. Should you have any questions, please contact us without hesitate.

    Best Regards,

    Zhi-ming Zhao

    Here below is our description on revision according to the reviewers’ comments.
    Response to Reviewer 1#
    Date: July 12, 2020
    Thank you very much for your constructive comments on our manuscript entitled “Theoretical and Experimental Dynamics Analysis of Rotor bearing System Supported by Elliptical Bearings” submitted to INDUSTRIAL LUBRICATION AND TRIBOLOGY. We have studied these comments carefully and have made corrections and explanations which we hope meet with approval. Revised portion are marked yellow in the revised manuscript which is attached in the end of this file. With regard to your comments, we wish to reply as follows:

    Comment 1: In introduction section, the previous work should be mentioned in some details to clarify the differences between their approaches and techniques. Therefore, the entire introduction should be rewritten and streamlined.
    Response:
    Thank you for your helpful suggestions. The introduction section has been rewritten marke yellow in the manuscript.

    Comment 2: Generally, what is the application of this bearing? This is should mentioned in the introduction section.
    Response:
    Thank you for your helpful advices. Elliptical bearing is a kind of bearings with large load capability compared with tilting pad bearings and high dynamic stability compared with cylindrical bearings. So the elliptical bearing usually be used to surport the low-pressure rotor system with large load and high stability in a steam turbine system. The bearings mentioned in this paper was used in certain kind of generator. This has been revised in section 1 marked yellow.

    Comment 3: In Numerical model (2.1): the background theory should be enlarged to contain the physical and computational domain on which the mathematical equations are represented. The solution algorithm should be mentioned and discussed in this paper.
    Response:
    Thank you for your helpful suggestions. The following explanations have been added to the manuscript in 2.1 section which are market yellow.
    When caculating the dynamic coefficients of the elliptical bearing, the following parameters of the bearing are needed: diameter, width, ellipcity, wrap angle and clearance. The woking parameters of rotor-bearing system are also needed such as viscocity of lubricant, inlet lubricant temperature, load of bearing and different speeds.
    The caculation procedures are given as follows 1) Input the inertial parameters to solve the steady Renolds equation by finite difference method, and obtain the steady state pressure, the eccentricity ratio and the attitude angle; 2) Solve the perturbed Reynolds equations and obtain the perturbed oil pressure by finite difference method,; 3) Caculate the stiffness and damping coefficients; 4) By coordinate transformation, the stiffness and damping coefficients including Kxx, Kxy, Kyx, Kyy, Cxx, Cxy, Cyx and Cyy can be obtained.

    Comment 4: Physical explanation for results in theoretical simulation results (2.2) shown in figure 2, figure 3, figure 4 and figure 5 should be mentioned in this paper.
    Response:
    Thank you for your helpful addvices. The physical explanations are added to section 2.2.1 and 2.2.2 marked yellow.

    Comment 5: A detail for test bearing and test bed should be mentioned in this paper.
    Response:
    Thank you for your helpful addvices. The detail of test bearing and test bed are added to section 3.1 marked yellow.

    Comment 6: Some physical explanation for the results shown in figure 7.
    Response:
    Thank you for your helpful addvices. The physical explanations are added to section 3.2 marked yellow.

    Comment 7: There should be a full nomenclature of all the mathematical symbols used.
    Response:
    Thank you for your helpful suggestions. All of the mathematical symbols used in manuscript have been sorted out in section 2.1 marked yellow.

    Comment 8: Missing comma after the introductory phrases in many places through the manuscript
    Response:
    Thank you for your helpful suggestions. We are so sorry with this kind of mistakes. We have revised them in manuscript.

    Comment 9: Missing articles (a, an or the ) in many places through the manuscript.
    Response:
    Thank you for your helpful suggestions. We have revised them in manuscript.

    Comment 10: The word "And" is not correct at the beginning of the sentence.
    Response:
    Thank you for your helpful suggestions. We have revised them in manuscript.

    Comment 11: Some writing errors:
    -Numerical model
    -1st paragraph, page 1 line 1 "is shown in figure 1 and ....."
    -This sentence should be rephrased "There are two bearings using in rotor bearing system using for certain kind of power generation equipment".
    -In Vibration analysis section, third line in first paragraph "Figure 7 shown…) should be replaced by "Figure 7 shows……"
    -In Vibration analysis section, second paragraph, second line "The Figure 7(a),,,," should be replaced by "Figure 7(a) ……". The same for The figure 7(b) shown…, the word the should be omitted and shows instead of shown.
    Response:
    Thank you for your helpful suggestions. We are so sorry with this kind of mistakes. We have revised them in manuscript.
    Response to Reviewer 2#
    Date: July 12, 2020
    Thank you very much for your constructive comments on our manuscript entitled “Theoretical and Experimental Dynamics Analysis of Rotor bearing System Supported by Elliptical Bearings” submitted to INDUSTRIAL LUBRICATION AND TRIBOLOGY. We have studied these comments carefully and have made corrections and explanations which we hope meet with approval. Revised portion are marked red in the revised manuscript which is attached in the end of this file. With regard to your comments, we wish to reply as follows:

    Comment 1: In the abstract, designed method of large diameter elliptical bearings has been mentioned. However, it has not been described in the manuscript.
    Response:
    Thank you for your kind suggestions. The disigned method of elliptial bearing mentioned in this manuscript concludes two aspects. One is the mumerical model and numeirical simulation, and the other is the experimental identification techonique. I have added this opinion to the manuscript marked red. Maybe it is not so suitable, but that’s the authors opinions.

    Comment 2: It has been demonstrated that from 500 to1500 rpm, the rotor system is under stable condition. It would be good if the limiting speed range for the rotor with such large elliptical bearings could be determine through numerical analysis.
    Response:
    Thank you for your kind advices. Although the numerical analysis can be used to caculate the dynamics characteristics of bearings, the critical speed obtained will be with certain errors due to the limitation of numerical model. In order to make the results more applicable, expecially the first-order critical speed, the experimental research is also explored. The analysis combined mumerical and experimental analysis may be a feasible way for designning the large diameter elliptical bearings.

    Comment 3: Fig 1. Only one view of orthographic projection is provided. For better understanding, at least 2 views should be provided.
    Response:
    Thank you for your kind suggestions. The aim to show Fig 1 is to give a schematic diagram for elliptical bearing. It is not a design drawing which might be not proper to show in a research paper. The main parameters are given in table 1 which might make it much beter understanding for readers. The changes have been marked red in section 2.1, 2.2 and 3.1.

    Comment 4: Page 2, line 32: “Compared with present elliptical bearings, the bearings studied in this paper is a large bearing not only in large diameter but also in heavy load capability”. In the present context with which bearing comparison is being made?
    Response:
    Thank you for your useful advices. I am so sorry for the missstatement. This centance was changed to “The large elliptical bearings studied in this paper is a bearing with large diameter and heavy load” which is marked red in section 2.2.

    Comment 5: Page 3, line 32:“After dimensionless transformation and omitting small amount--” Rewrite the statement.
    Response:
    Thank you for your useful advices. The statement was replaced by “After dimensionless transformation, the Reynolds equation can be written as” which has been changed in the manuscript marked red in section 2.1.

    Comment 6: Page 4, line 22-23: “The change law of stiffness coefficients reflects that the bearing capacity of elliptical bearing in direction y is better than direction x”. What does authors’ mean to state, has not been clearing conveyed.
    Response:
    Thank you for your kind suggestions. From Fig 2(a), the main stiffness of vetical direction (Kyy) coefficients are bigger than that of horizontal direction (Kxx). So the elliptical bearing cappbility of vetical direction is better than that of horizontal direction. The statement is replaced by “The change rule of the main stiffness shows that the bearing capacity of the elliptical bearing in the vertical direction is better than that in the horizontal direction”.

    Comment 7: Page 4, line 17-18: “In the same speed the stiffness coefficients decreases with the increase of L/D” such grammatical mistakes are noticed in the manuscript.
    Response:
    Thank you for your kind suggestions. The statement is replaced by “In the same speed the stiffness coefficients decrease as the L/D increases.” Marked red in section 2.2.1

    Comment 8: Fig 2 A: why kxx is greater than kyy. Why speed and L/D have no influence on kxx. Why kyy decreases with increase with speed and L/D ratio. Physical reasoning should be provided.
    Response:
    Thank you for your useful advices.
    First, in fig 2(a) the Kyy is greater than Kxx. As your mentioned “why kxx is greater than kyy.”, the possiable reason is that the difference between the upward triangle mark and the left triangle mark in the Fig 2(a) is not obviouse.
    Secondly, as mentioned “Why speed and L/D have no influence on kxx”, actualy there are certain influences. The reason why the changing trend is not obvious is that the Kxx values of different speeds are between 1.5×10^9N/m to 2.5×10^9N/m.
    Thirdly, the reason why Kyy decreases with increase with speed and L/D ratio is as follows: as the rotation speed increases, the eccentricity decreases, the oil film thickness increases, and the oil film squeeze effect is weakened, which causes the bearing stiffness of vertical dirction (y direction) to decrease. The explanation is added to the section 2.2.2 marked red.

    Comment 9: Physical reasoning should also be provided for the behavior shown in Figs. 2B and 3A and 3B.
    Response:
    Thank you for your helpful addvices. The physical explanations are added to section 2.2.1 marked red.

    Comment 10: Brief description about the procedure adopted for numerical simulation may be provided.
    Response:
    Thank you for your useful advices. The brief description about the procedure is as follows which has been added to section 2.1 marked red.
    The caculation procedures are given as follows 1) Input the inertial parameters to solve the steady Renolds equation by finite difference method, and obtain the steady state pressure, the eccentricity ratio and the attitude angle; 2) Solve the perturbed Reynolds equations and obtain the perturbed oil pressure by finite difference method,; 3) Caculate the stiffness and damping coefficients; 4) By coordinate transformation, the stiffness and damping coefficients including Kxx, Kxy, Kyx, Kyy, Cxx, Cxy, Cyx and Cyy can be obtained.

    Comment 11: Page 4, line 60: “Buy the main damping coefficients of direction x are no obvious changes with speeds”. Typing mistake is noticed.
    Response:
    Thank you for your useful advices. We have checked the manuscript carefully to correct these typing mistakes.

    Comment 12: Photograph of experimental set-up may be provided.
    Response:
    Thank you for your useful suggestions. The potograph of experiment set-up is not proper to used in publication. In my opion, the Fig 6 and Table 1 can make readers understand the experiment set-up and test bearing clearly.

    Comment 13: Experimental and theoretical values of stiffness and damping coefficients are not in agreement. How much experimental and theoretical values are deviated should be provided.
    Response:
    Thank you for your useful suggestions. The identified results by experiment vibration data show that 1) the error of the stiffness and damping coefficients in horizontal dirction (x direction) is small. The deviations of stiffiness coefficients and damping coefficients are no more than 50%; 2) the error of the coefficients in vertical direction (direction y) is much bigger. The possible reason might be that the stiffness and damping coefficients identified by experiment are the comprehensive coefficients which include the stiffness and damping of the bearing housing, oil film and the shaft. Therefore, there are much bigger differences between the experimental value and the theoretical values. The revised part has been added to section 3.3 marked red.

    Comment 14: Even though experimental and theoretical values of stiffness and damping coefficients are not in agreement; however, critical speed calculated through numerical simulation are in good agreement. Why it is so?
    Response:
    Thank you for your useful suggestions. It can be seen that the first critical speed obtained by theoritical analysis and experimental identification are near to 800rpm and 650rpm, respectively. From the experimentla identified results it can be seen that the critical speed is much lower than theoretical results. The main reason is the the stiffness and damping coefficients difference between the theoritical and experimental analysis mentioned in the reply of common 13. The revised part has been added to section 3.3 marked red.

    Comment 15: In the conclusions section, page 8, line: 46 to 47, 3rd conclusion: “The design method for rotor system supported by large diameter elliptical bearing can be obtained by the theoretical and experimental results shown in this paper” In the manuscript, design method is not described. What does authors mean to express should be described in detail.
    Response:
    Thank you for your kind suggestions. The disigned method of elliptial bearing mentioned in this manuscript concludes two aspects. One is the mumerical model and numeirical simulation, and the other is the experimental identification techonique. I have added this opinion to the manuscript. Maybe it is not so suitable, but that’s the authors opinions.



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  • pre-publication peer review (ROUND 1)
    Decision Letter
    2020/05/11

    11-May-2020

    Dear Dr. Zhao:

    Manuscript ID ilt-04-2020-0122 entitled "Theoretical and Experimental Dynamics Analysis of Rotor-bearing System Supported by Elliptical Bearings" which you submitted to the Industrial Lubrication and Tribology, has been reviewed. The comments of the reviewer(s) are included at the bottom of this letter.

    The reviewer(s) have recommended major revisions to the submitted manuscript, before it can be considered for publication. Therefore, I invite you to respond to the reviewer(s)' comments and revise your manuscript.

    To revise your manuscript, log into https://mc.manuscriptcentral.com/ilt and enter your Author Centre, where you will find your manuscript title listed under "Manuscripts with Decisions." Under "Actions," click on "Create a Revision." Your manuscript number has been appended to denote a revision.

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    Once again, thank you for submitting your manuscript to the Industrial Lubrication and Tribology and I look forward to receiving your revision.

    Sincerely,
    Prof. Carsten Gachot
    Editor, Industrial Lubrication and Tribology
    carsten.gachot@tuwien.ac.at

    Reviewer(s)' Comments to Author:
    Reviewer: 1

    Comments to the Author
    In the present work, Stiffness and damping coefficients of hydrodynamic elliptical bearings are determined through numerical analysis and further applied in rotor dynamics. In addition, experimental measurement of FRF related to rotor-bearing system were obtained. Then, stiffness and damping of the elliptical bearings were extracted from the measured FRF. Numerical results are compared with experimental result.
    The reviewer agrees that authors have addressed an important aspect from bearing design and its influence on rotor dynamics. The paper may be accepted; however, authors need to provide the justification for issues as mentioned in the attachment.

    Reviewer: 2

    Comments to the Author
    (There are no comments.)
    Reviewer: 1

    Recommendation: Major Revision

    Comments:
    In the present work, Stiffness and damping coefficients of hydrodynamic elliptical bearings are determined through numerical analysis and further applied in rotor dynamics. In addition, experimental measurement of FRF related to rotor-bearing system were obtained. Then, stiffness and damping of the elliptical bearings were extracted from the measured FRF. Numerical results are compared with experimental result.
    The reviewer agrees that authors have addressed an important aspect from bearing design and its influence on rotor dynamics. The paper may be accepted; however, authors need to provide the justification for issues as mentioned in the attachment.

    Additional Questions:
    Originality: Does the paper contain new and significant information adequate to justify publication?: In the present work, Stiffness and damping coefficients of hydrodynamic elliptical bearings are determined through numerical analysis and further applied in rotor dynamics. In addition, experimental measurement of FRF related to rotor-bearing system were obtained. Then, stiffness and damping of the elliptical bearings were extracted from the measured FRF. Numerical results are compared with experimental result. The reviewer agrees that authors have addressed an important aspect from bearing design and its influence on rotor dynamics.

    Relationship to Literature: Does the paper demonstrate an adequate understanding of the relevant literature in the field and cite an appropriate range of literature sources? Is any signficant work ignored?: yes

    Methodology: Is the paper's argument built on an appropriate base of theory, concepts, or other ideas? Has the research or equivalent intellectual work on which the paper is based been well designed? Are the methods employed appropriate?: yes.

    Results: Are results presented clearly and analysed appropriately? Do the conclusions adequately tie together the other elements of the paper?: yes. some comments are provided in the attachment.

    Practicality and/or Research implications: Does the paper identify clearly any implications for practice and/or further research? Are these implications consistent withthe findings and conclusions of the paper?: yes

    Quality of Communication: Does the paper clearly express its case, measured against the technical language of the field and the expected knowledge of the journal's readership? Has attention been paid to the clarity of expression and readability, such as sentence structure, jargon use, acronyms, etc.: yes.
    few grammatical mistakes are noticed.

    Reproducible Research: If appropriate, is sufficient information, potentially including data and software, provided to reproduce the results and are the corresponding datasets formally cited?: yes

    This journal is participating in Publons Transparent Peer Review. By reviewing for this journal, you agree that your finished report, along with the author’s responses and the Editor’s decision letter, will be linked to from the published article to where they appear on Publons, if the paper is accepted. If you have any concerns about participating in the Transparent Peer Review pilot, please reach out to the journal’s Editorial office. Please indicate below, whether you would like your name to appear with your report on Publons by indicating yes or no. All peer review content displayed here will be covered by a Creative Commons CC BY 4.0 license.: Yes, I would like my name to appear with my report on Publons

    Reviewer: 2

    Recommendation: Minor Revision

    Comments:
    (There are no comments.)

    Additional Questions:
    Originality: Does the paper contain new and significant information adequate to justify publication?: It contains sufficient original contributions for publication in a journal

    Relationship to Literature: Does the paper demonstrate an adequate understanding of the relevant literature in the field and cite an appropriate range of literature sources? Is any signficant work ignored?: needs more details

    Methodology: Is the paper's argument built on an appropriate base of theory, concepts, or other ideas? Has the research or equivalent intellectual work on which the paper is based been well designed? Are the methods employed appropriate?: yes

    Results: Are results presented clearly and analysed appropriately? Do the conclusions adequately tie together the other elements of the paper?: I have made some suggestions and a couple of queries for the author's attention

    Practicality and/or Research implications: Does the paper identify clearly any implications for practice and/or further research? Are these implications consistent withthe findings and conclusions of the paper?: There is adequate discussions and conclusions of the results in the paper. I have queried as to the application of some of the results in my communication for the author

    Quality of Communication: Does the paper clearly express its case, measured against the technical language of the field and the expected knowledge of the journal's readership? Has attention been paid to the clarity of expression and readability, such as sentence structure, jargon use, acronyms, etc.: yes

    Reproducible Research: If appropriate, is sufficient information, potentially including data and software, provided to reproduce the results and are the corresponding datasets formally cited?:

    This journal is participating in Publons Transparent Peer Review. By reviewing for this journal, you agree that your finished report, along with the author’s responses and the Editor’s decision letter, will be linked to from the published article to where they appear on Publons, if the paper is accepted. If you have any concerns about participating in the Transparent Peer Review pilot, please reach out to the journal’s Editorial office. Please indicate below, whether you would like your name to appear with your report on Publons by indicating yes or no. All peer review content displayed here will be covered by a Creative Commons CC BY 4.0 license.: Yes, I would like my name to appear with my report on Publons

    Decision letter by
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    Reviewer report
    2020/05/11

    This reviewer report was submitted to the journal as an attached file and cannot be displayed at this time.

    Cite this review
    Reviewer report
    2020/05/04

    In the present work, Stiffness and damping coefficients of hydrodynamic elliptical bearings are determined through numerical analysis and further applied in rotor dynamics. In addition, experimental measurement of FRF related to rotor-bearing system were obtained. Then, stiffness and damping of the elliptical bearings were extracted from the measured FRF. Numerical results are compared with experimental result.
    The reviewer agrees that authors have addressed an important aspect from bearing design and its influence on rotor dynamics. The paper may be accepted; however, authors need to provide the justification for issues as mentioned in the attachment.

    Reviewed by
    Cite this review
All peer review content displayed here is covered by a Creative Commons CC BY 4.0 license.