Monitoring Metal Wear Particles of Friction Pairs in the Oil Systems of Gas Turbine Power Plants

Round 1

Reviewer 1 Report

 

1. One of the main elements of the measurement method used is the division of the flow into parts. However, there is no information in the article about how many individual channels are recommended to be used and how many parts are actually used in the presented laboratory experiments and tests on the engine stand.
2. Dimensions and weight characteristics of the measuring system are not given and are not discussed. Judging by Fig. 4 and 5, they are significant.
3. When describing the processing algorithm, it is necessary to indicate the sensitivity threshold used to determine the presence or absence of a signal. Questions about the content of the processing algorithm can be continued. So, for example, how the algorithm reacts if one of the two signals is not recognized (for example, the first signal in Fig. 7, b). What is the signal-to-noise ratio in laboratory and real conditions?
4. It is not clear from the text how the calibration characteristics were obtained, representing the dependence of the signal level on the distance to the particle, presented in Table. one.
5. The assumption that the particles move at the same speed as the flow (lines 353, 354) is incorrect, since the particles collide with the walls, slow down and change the trajectory, which follows from Fig. 7.
6. The results of laboratory tests are not accompanied by a reliability analysis and an assessment of the accuracy of the results.

Author Response

Dear Reviewer,

the authors would like to express their sincere thanks for the constructive and precious comments that gave us a chance to improve the article. We carefully studied all the comments, questions, and suggestions and have revised the manuscript accordingly. Our responses in point-by-point manner are given below.

Point 1: One of the main elements of the measurement method used is the division of the flow into parts. However, there is no information in the article about how many individual channels are recommended to be used and how many parts are actually used in the presented laboratory experiments and tests on the engine stand.

Response 1: As it is rightly pointed out, the main idea of the proposed method is the separation of the general oil flow on the sensor input into N independent flows with a smaller cross-section area. The main conditions of such separation are (lines 140-146):

1. The sensor should not work as a debris filter.
2. The acceptable sensitivity of the sensor to the smallest of the detectable metal particles should be ensured.
3. The overall cross-sectional area of all N flows should be roughly equal to the total oil flow area on the sensor's input.

The initial task was to detect ferromagnetic and non-ferromagnetic particles with the equivalent sizes from 0.3 up to 0.8 mm in the pipeline of 20 mm. For this purpose, we used 6-channel sensor with inner diameter of each channel equal to 8 mm. Relevant information has been added to the text of the article (lines 547-549).

Point 2: Dimensions and weight characteristics of the measuring system are not given and are not discussed. Judging by Fig. 4 and 5, they are significant.

Response 2: We had no significant restrictions on system size and weight at the current stage of works. Both variants of the sensors were made in the same design. The overall dimensions and mass characteristics of the sensors have been added to the text (lines 549-550).

Point 3: When describing the processing algorithm, it is necessary to indicate the sensitivity threshold used to determine the presence or absence of a signal. Questions about the content of the processing algorithm can be continued. So, for example, how the algorithm reacts if one of the two signals is not recognized (for example, the first signal in Fig. 7, b). What is the signal-to-noise ratio in laboratory and real conditions?

Response 3: Thank you for the comment. Of course, the experiments in the laboratory and on the stand differ in noise and interference sources. We have added the relevant information about the amplitude of the “noise” signal that defines the “discrimination” zone in amplitude detection procedure and in fact is the sensitivity threshold used to determine the presence or absence of the informational signal at the MC output to the text of the article (lines 577-582 and lines 621-627). The existence of two consecutive pulses of the opposite polarity on the fixed distance when the particles pass through the oil channel of the sensor is a good diagnostic property that makes it possible to identify a signal at the sensor output as a signal from a chip (lines 234-237). So, if there is only one pulse in the signal, the algorithm will recognize it as an interference. At the same time, it should be noted that the noise protection of the system components and the improving of the algorithms of signal detection and particle recognition are the urgent challenges for us.

Point 4: It is not clear from the text how the calibration characteristics were obtained, representing the dependence of the signal level on the distance to the particle, presented in Table. one.

Response 4: We have added the description of the calibration process to the text (lines 321-328).

Point 5: The assumption that the particles move at the same speed as the flow (lines 353, 354) is incorrect, since the particles collide with the walls, slow down and change the trajectory, which follows from Fig. 7.

Response 5: This is a discussion issue that requires further research. Fig. 6 demonstrates that the oil flow was pressed against the lower left wall of the pipeline. One of the reasons for this may be that the sensor was installed just behind the pipeline bend. The chip trajectories in Fig. 7 may also be caused by this reason.

Point 6: The results of laboratory tests are not accompanied by a reliability analysis and an assessment of the accuracy of the results.

Response 6: The proposed debris monitoring system is not the measuring system. In practice the determination of the exact size of the wear particle is often useless. To determine the defect nature in the bearing it is sufficient to assign particles to a size group and to track the frequencies of chips occurrence in the oil. That is why the metrology is not applicable in this case. And the reliability analysis will be considered in our further work.

We hope the manuscript is now suitable for publication.

Sincerely,
the authors.

Author Response File: Author Response.pdf

Reviewer 2 Report

1) The Abstract is too general and mainly descriptive. In the Abstract the Authors should add some of the most important results obtained in this research (its exact values). Such addition will highlight the novelty of the presented paper already in the Abstract and it will be clear what are the major findings obtained in the research.

2) In the paper must be added a Nomenclature inside which will be listed and explained all abbreviations, symbols and markings used throughout the paper text. A Nomenclature will significantly improve the paper reading experience, because at the moment the reader is required to turn back through the paper several times during reading to find the proper meaning of several abbreviations, symbols and markings. A presentation of all mentioned in one place will surely be helpful.

3) It is clear from the paper text, but I believe it will be helpful that the Authors directly state that the used DCMS hardware variant in the laboratory tests is the one from Figure 4 (b).

4) The experiments were performed in a laboratory. The Authors should add in the paper a brief discussion related to the possible problems and challenges which can be expected (in regards to the presented equipment and measuring process) in real exploitation conditions.

5) The English is understandable, but it should be improved in many sentences. For example, in Line 366 it is written: “the time of the passage of the distance” – the number of terms: “of the” should be reduced. Another example – Line 367 – the sentence cannot start with: “And vice versa”. Please, perform careful check and corrections related to English throughout the paper text.

6) In Table 2 the Authors have presented that three Tests were performed (Test 1, Test 2 and Test 3). First of all, it is unclear for which Test the Authors have presented results in a current paper version. Secondly, the paper should be enlarged with obtained results in the other two Tests.

7) As the Abstract, the Conclusions section should also be improved with the most important obtained results (its exact values). Also the Conclusions seem to be too descriptive and general, without any details obtained in the presented analysis.

 

Final remarks: This is a very interesting paper with quality-performed experimental research. During the revision process, please include in the paper more results obtained during the experiments and clarify what difficulties and challenges can be expected in real exploitation of such system. I hope that after proper revision (according to my comments above) this paper will have my recommendation for publication.

Author Response

Dear Reviewer,

the authors would like to express their sincere thanks for the constructive and precious comments that gave us a chance to improve the article. We carefully studied all the comments, questions, and suggestions and have revised the manuscript accordingly. Our responses in point-by-point manner are given below.

Point 1: The Abstract is too general and mainly descriptive. In the Abstract the Authors should add some of the most important results obtained in this research (its exact values). Such addition will highlight the novelty of the presented paper already in the Abstract and it will be clear what are the major findings obtained in the research.

Response 1: Thank you for the recommendation. We have significantly expanded the Abstract by adding some of the most important results obtained in the research (lines 16-32).

Point 2: In the paper must be added a Nomenclature inside which will be listed and explained all abbreviations, symbols and markings used throughout the paper text. A Nomenclature will significantly improve the paper reading experience, because at the moment the reader is required to turn back through the paper several times during reading to find the proper meaning of several abbreviations, symbols and markings. A presentation of all mentioned in one place will surely be helpful.

Response 2: Thanks again for the recommendation. The template to the manuscript preparing (https://www.mdpi.com/files/word-templates/energies-template.dot) does not provide such section, but we agree with the opinion of the respected reviewer that it’s very hard to read a manuscript without the appropriate section. We have added a list of abbreviations to the paper (lines 36-70).

Point 3: It is clear from the paper text, but I believe it will be helpful that the Authors directly state that the used DCMS hardware variant in the laboratory tests is the one from Figure 4 (b).

Response 3: We have added more detailed description of the sensor used in the experiments (lines 547-550)

Point 4: The experiments were performed in a laboratory. The Authors should add in the paper a brief discussion related to the possible problems and challenges which can be expected (in regards to the presented equipment and measuring process) in real exploitation conditions.

Response 4: Of course, the experiments in the laboratory and in real conditions on the stand are different, particularly in the sources of noise and interferences. That is why the noise protection of the system components and the improving of the algorithms of signal detection and particle recognition are the urgent challenges for us. The relevant information have been added to the paper (lines 577-582, 621-627, 724-728).

Point 5: The English is understandable, but it should be improved in many sentences. For example, in Line 366 it is written: “the time of the passage of the distance” – the number of terms: “of the” should be reduced. Another example – Line 367 – the sentence cannot start with: “And vice versa”. Please, perform careful check and corrections related to English throughout the paper text.

Response 5: Thanks for your valuable suggestion. We have carefully proofread the manuscript to eliminate all the language issues as many as we can. We hope the revised manuscript can meet your approval.

Point 6: In Table 2 the Authors have presented that three Tests were performed (Test 1, Test 2 and Test 3). First of all, it is unclear for which Test the Authors have presented results in a current paper version. Secondly, the paper should be enlarged with obtained results in the other two Tests.

Response 6: Table 2 presents the results of all three tests as well as the discussion in lines 588-598. We apologize for the ambiguities in the results description and have added some comments to lines 591, 594.

Point 7: As the Abstract, the Conclusions section should also be improved with the most important obtained results (its exact values). Also the Conclusions seem to be too descriptive and general, without any details obtained in the presented analysis.

Response 7: We have expanded the Conclusion with most important results of our research (lines 698-728).

Final remarks: This is a very interesting paper with quality-performed experimental research. During the revision process, please include in the paper more results obtained during the experiments and clarify what difficulties and challenges can be expected in real exploitation of such system. I hope that after proper revision (according to my comments above) this paper will have my recommendation for publication.

Response: Thank you for the appreciation of our work. In this revision all your comments and suggestions have been carefully considered. We hope that our responses to comments can answer your questions and meet your standard for publication.

Sincerely,
the authors

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The Authors have performed all mentioned corrections/additions/improvements. Now, after revision, I have no more concerns related to this paper. My congratulations to the Authors.