Effect of Adding Hexagonal Boron Nitride (hBN) Nano-Powder to Lubricant on Performance and Emissions in a Two-Stroke Gasoline Engine

Round 1

Reviewer 1 Report

The author has provided an interesting study, however, due to the lack of how this manuscript is novel and current written format, it is difficult to accept this manuscript in its current form. Suggestions are made below, and the Reviewer is happy to review again upon amendments.  

 

Major:

 

1.       Although the literature (introduction) section provides a high level understanding of how this manuscript is novel, both the abstract and conclusion was not clear enough.

a.       The Reviewer is a strong advocate to improving existing technology while newer technology such as electrification matures and becomes more readily available. However, the abstract and conclusion provides no real justification how this work is relevant in modern times.

b.       By addressing the previous point (1a) the novelty of the manuscript may become more clearer – note paragraph starting on line 87 and line no. 92 does provide some sort of insight on the matter; but a more comprehensive explanation is needed.

c.       How does this manuscript aid in sustainability?

                                                               i.      Again, an explanation could help understanding the novelty.

2.       The general structure of the manuscript is fine; however, written style is very repetitive or constructed sentences are unnecessarily long/ or provide no real meaning.

a.       E.g. Line 156: ‘In this study, a power generator was used in the experiments and the alternators in them work at a constant frequency. Therefore, the internal combustion engine in the power generator runs at constant speed.’

                                                               i.      This sentence could have been reduced to, ‘In this study, power generators run at constant speed due to the fact the alternator was set at a constant frequency.’ 

b.       E.g. Line 256: ‘Generators are machines operating at constant speed and therefore constant speed variable load experiments have been carried out. As a result, reducing the amount of oil results in improved emissions and poor performance.’

                                                               i.      How does constant speed a boundary condition imposed by the author improve emissions and performance?

 

Sadly, in this current state it is very difficult to accept publication.

 

 

 

See earlier comments

Author Response

1. Although the literature (introduction) section provides a high level understanding of how this manuscript is novel, both the abstract and conclusion was not clear enough.
   The entire paper has been reviewed and revised. 
2. The general structure of the manuscript is fine; however, written style is very repetitive or constructed sentences are unnecessarily long/ or provide no real meaning.
   The entire paper has been reviewed and revised. 

Reviewer 2 Report

This manuscript consist of original researches. Inreasing of the load and adding of the hBN leads to decrease of the specific fuel consumption. Also, the addition of hBN results to ehgine operating conditions are getting closer to full combustion was reported. Emission was improved by additive due to the increasin of CO2 and decreasing of CO.Results and comments are very important and usefull for literature, science and technology.  Some results might be given at the end of the abstract. 

This manuscript might be edited by native speaker.

Author Response

1. This manuscript consist of original researches. Inreasing of the load and adding of the hBN leads to decrease of the specific fuel consumption. Also, the addition of hBN results to ehgine operating conditions are getting closer to full combustion was reported. Emission was improved by additive due to the increasin of CO2 and decreasing of CO.Results and comments are very important and usefull for literature, science and technology.  Some results might be given at the end of the abstract.
   thanks for your comment. According to your comment, the necessary revision has been made in the paper.

Reviewer 3 Report

 

The manuscript has tried evaluating the effect of hBN NPs on emissions and lubricants emissions in a two-stroke gasoline engine. The study shows the effectiveness of hBN NPs in decreasing emissions and overall performance.

However, in general, the study is poorly presented and discussed. Specifically, the result section is not elaborated/analysed and discussed adequately, the Abstract is ambiguous, and does not provide any specific information scientifically; the Introduction hardly provides any literature.

More importantly, the authors need to support the novelty since a similar article is already published " https://onlinelibrary.wiley.com/doi/full/10.1002/eng2.12216".  It appears that the authors desperately avoided similar literature in the introduction and manuscript.

Here are some of critical technical comments concerning the manuscript:

1.      Hbn NPs have been widely studied as lubricants additive; there are so many scientific articles. However, I could find any in literature. Please add a Table for previous HbN NPs as an additive and lubrications performance and mechanisms.

2.      Authors should explain what was the primary reason of the selection of hBN over other NPs which has shown better lubrication prospects in tribology studies. Authors can checkout the comparative performance of nano lubricants here “https://www.sciencedirect.com/science/article/pii/S0301679X23001196”

3.      NPs are not characterized in the manuscript (SEM/ TEM for shape). Since it is known the size of NPs can affect their performance. Authors should add this in discussions.

4.      Why Oleic acid was chosen, since it is itself a boundary lubricant, how do authors differentiate the effect of oleic acid from hbn? Rather, dispersant could have been a better choice; Which could have improved the shelf life of oils.

5.      In support of acclaimed shelf life 120 hours is too low. Please include a schematic of the preparation and oil pictures

6.      Line 56-60 does not add any correlation to current work and therefore can be removed. Instead, literature on Different NPs as an additive along with their potential mechanism can be discussed in detail. The author can refer to some of  “https://doi.org/10.1016/j.molliq.2020.115238 , https://journals.sagepub.com/doi/full/10.1177/1350650120940173” for lubrication mechanism and different NPs.

7. The Fig 4-8-line colours can be modified (for NPs added oils) for easy accessibility.

8.      The Results and Discussion section are rather descriptive, authors should be discussed in detail and should include quantification of improvements, and point out the primary reason for improvements through support of published literature.

9.      Authors should include a details analysis of change in CO, HC, Co2 emission. Why? Reduction

10.   Please include details of Chosen Oil Synthetic. Mineral?

 

• Some of the lines in the introduction are written casually, with incomplete information & references, authors are suggested to go through and improvise the whole section. 

 

After careful consideration of the points, it is my opinion that the current manuscript does not provide new scientific inputs and needs major substantial revision to fit into possible publications standard.

• Some of the lines in the introduction are written casually, with incomplete information & references, authors are suggested to go through and improvise the whole section. 

Author Response

1. Hbn NPs have been widely studied as lubricants additive; there are so many scientific articles. However, I could find any in literature. Please add a Table for previous HbN NPs as an additive and lubrications performance and mechanisms.
   More detailed explanations are given about the effects of hBN on lubricity.
2. Authors should explain what was the primary reason of the selection of hBN over other NPs which has shown better lubrication prospects in tribology studies. Authors can checkout the comparative performance of nano lubricants here “https://www.sciencedirect.com/science/article/pii/S0301679X23001196”
   It is explained why we prefer hBN.
3. NPs are not characterized in the manuscript (SEM/ TEM for shape). Since it is known the size of NPs can affect their performance. Authors should add this in discussions.
   Since this study focuses on the effects of hBN on the engine, no in-depth study of the lubricity of hBN has been performed. However, since there are enough studies on this subject in the literature, these characteristics of hBN have been cited to.
4. Why Oleic acid was chosen, since it is itself a boundary lubricant, how do authors differentiate the effect of oleic acid from hbn? Rather, dispersant could have been a better choice; Which could have improved the shelf life of oils.
   In order to understand what kind of effect oleic acid has when added to engine oil, 3% oleic acid was added to the oil and tests were carried out on the engine. However, as a result of the experimental results, it was concluded that the addition of oleic acid did not have a significant effect on engine performance.
5. In support of acclaimed shelf life 120 hours is too low. Please include a schematic of the preparation and oil pictures
   In fact, the waiting time of 120 hours is very short and unacceptable according to the literature. However, in two-stroke engines, the fuel-oil mixture is prepared before use and mixed mechanically. So there is no long wait. In the light of this information, it has been predicted that 120 hours is a sufficient/reasonable time.
6. Line 56-60 does not add any correlation to current work and therefore can be removed. Instead, literature on Different NPs as an additive along with their potential mechanism can be discussed in detail. The author can refer to some of  “https://doi.org/10.1016/j.molliq.2020.115238 , https://journals.sagepub.com/doi/full/10.1177/1350650120940173” for lubrication mechanism and different NPs.
   More detailed information is given on this issue.
7. The Fig 4-8-line colours can be modified (for NPs added oils) for easy accessibility.
   Figures have not been changed since it is assumed that the paper can be used by printing black and white.
8. The Results and Discussion section are rather descriptive, authors should be discussed in detail and should include quantification of improvements, and point out the primary reason for improvements through support of published literature.The mentioned section has been revised.
9. Authors should include a details analysis of change in CO, HC, Co2 emission. Why? Reduction
   More detailed information on emissions is given.
10. Please include details of Chosen Oil Synthetic. Mineral?
    Mineral oil was used in this study and a fuel:oil ratio of 100:4 is recommended according to catalog data. This information is also expressed in the paper.
    

Reviewer 4 Report

The article by Orman R.C. assesses the effect of boron nitride particles in lubricating oil on the performance of a two-stroke engine and its exhaust emission. The author uses different particle concentrations and various lubricant/fuel ratios and investigates their effect on fuel consumption, excess air ratio, exhaust gas temperature, and different gas emissions at different engine power outputs. The article is interesting and understandable written, although its English needs editing. In addition, in my opinion, the article is more appropriate for Lubricants than for Sustainability. Perhaps the author should strengthen the part about sustainability. In any case, the article needs to be revised before publication.

Specific comments are as follows.

Lines 11, 36: “Unusually”. The author probably meant "usually."

Line 18: “improved emissions”. Perhaps the author meant "reduced emissions".

Lines 35-40: These lines duplicate lines 10-14. The text should not be repeated twice, as it irritates the reader.

Lines 61-65: “However, in order…CuO (Copper oxide)[23],”. The sentence is incomplete because there is no predicate.

Line 73: “Today, there are many studies on the use of hexagonal shaped BN (hBN) nano powders as additives in lubricants”. Hexagonal boron nitride is also used to improve greases because it improves their antiwear properties and stabilizes friction over time (see, e.g., 10.1016/j.carbpol.2021.118509).

Line 106, 223, 240, 246, and elsewhere: “for exhaust gas analysis (HC, CO, CO2)”. There is no such gas as HC. This place is unclear. The same applies to Figure 1 and Table 2. What is Lambda in Table 2?

Line 128: “a 70 nm hBN nanopowder (Table 4) was mixed with mineral 2-stroke lubricant”. The mixing of nanoparticle powder with oil does not mean that the final dispersion will have boron nitride in nanoscale form, as its particles strongly aggregate. Can the author provide dynamic scattering data of the resulting lubricant to characterize the particle size of BN?

Line 135: “5 mL of hBN”. Boron nitride is a powder, and it is strange to measure it in ml. Its mass should be given.

Line 205: “excess air ratio”. It is worthwhile for the author to explain what this indicator is and how important it is.

Line 251: “the effect of nano hBN additive”. There is no evidence in the article that boron nitride is presented in nanoscale form.

Line 260: “However, 0.5% vol.” It is unclear what this sentence means.

Line 268: “thus the emission caused by the lubricating oil can be reduced”. That is fine. However, what about the possible content of boron nitride nanoparticles in the exhaust gas? How might dust from boron nitride nanoparticles affect the health of the population who will breathe this air? These points should be presented in the article at least as necessary for the study.

The English language needs moderate editing.

Author Response

thanks for your comments. Considering all comments, necessary revisions were made and the entire paper was reviewed.

Round 2

Reviewer 3 Report

The authors have failed to address the previous comments; the Results and Discussion sections are not discussed with appropriate scientific backing.Moreover, since Similar Studies are already published in better comprehensible ways such as "https://onlinelibrary.wiley.com/doi/full/10.1002/eng2.12216" and a few more; The current article does not justify any new novelty with presented results and discussions

The Revised manuscript is to  more cumbersome to comprehend (introduction section) 

The Revised manuscript is to  more cumbersome to comprehend (introduction section)  Need to Concise 

Author Response

Dear Reviewer 3

Thank you for your comments.
The paper has been revised based on your comments.

Reviewer 4 Report

The author almost completely ignored the comments and didn't even respond to them. There are some corrections, but they are not enough to publish the article in Sustainability. 

Comments remained as follows.

1. The introduction to this article does not contain a complete analysis of recent work on lubricating materials containing boron nitride. The author only cites references 24-33, but this list is incomplete and is not accompanied by a proper analysis of these works.
2. The author has not provided sufficient justification that his lubricant is suitable for sustainable applications. The fact that "CO2 increased and CO and HC decreased" refers to ecology but not to sustainable development. Sustainable development implies the use of biodegradable materials and materials from renewable sources. In the context of lubricants, this means the use of biodegradable base oils and/or naturally based oils. The author uses mineral oil as a base oil. Mineral oil is derived from fossil fuels and is completely non-biodegradable. The author's lubricant has nothing to do with sustainability.
3. The author adds boron nitride nanoparticles and writes "However, considering that the amount of oil in the fuel is 4% and the amount of hBN in the oil is 0.5%, there is 0.45 g of hBN in each liter of fuel. This value can be ignored for now, as hBN is non-toxic and does not react chemically." This comment is unacceptable. Previously, automobile fuel contained tetraethyllead in the same concentrations for years poisoning mankind and polluting the environment until it was banned. Boron nitride nanoparticles can also have similar harmful effects on humans, such as inducing lung cancer by being dispersed in the air after fuel combustion. This effect, for example, is produced by quartz particles that are non-toxic and do not react chemically.
4. The author provides no evidence that he actually uses boron nitride in the form of nanoparticles. Without clear evidence via light scattering and electron microscopy data, the claim of nanoparticles is speculation only.

These comments and the comments from the previous report should be adequately applied to improve the manuscript. In the current version, I cannot recommend it for publication.

The English language needs moderate editing.

Author Response

Dear Reviewer 4

Thank you for your comments.
The paper has been revised based on your comments.

You can see the SEM image of the hBN I used on the paper. I got support from another institution for the SEM image because I did not have enough opportunities. That's why it's a little late for me to do the revision. Thank you for your understanding.

Round 3

Reviewer 3 Report

The author has made improvements in the manuscript suggested.

Manuscript  can be considered for publication

 

Author Response

Thank you for your comments.

Reviewer 4 Report

The author has made some improvements to the manuscript but has not finalized the work.

First, the introduction of the article misleads the reader. For example, it states on line 94: “The use of nano additives such as BN (Boron nitride) [24-33] is also becoming widespread. It has been reported that thanks to these nano-additives, the tribological properties of the oil such as anti-wear performance, heat conductivity and viscosity improve [16, 20-23].”

However, references 16 and 20-23 do not provide information on the effect of boron nitride on the antiwear and viscosity properties of lubricating materials. At the same time, the work on studying the effect of boron nitride on antiwear and viscosity properties of lubricating materials has been nevertheless carried out, e.g. by Gorbacheva (Carbohydr. Polym., 2001, 272, 118509). The author has to check all references for the correctness of the information that they support.

Second, the author still does not present any proof that boron nitride is in nanoscale form in the lubricant and is indeed 70 nm in size as the author writes. The author provides SEM data. Well, the microscopy data show that the initial boron nitride particles have nanoscale dimensions. However, boron nitride particles have a polar surface, whereas the mineral oil that the author used is non-polar. This means that the boron nitride particles are very likely to aggregate entirely or at least partially in this oil and will not be nanoparticles. The author used oleic acid as a surfactant, but this does not mean that it will necessarily work and prevent nanoparticle aggregation. For this reason, if the author claims that boron nitride is presented as nanoparticles in the lubricant, he should prove it, e.g., by performing dynamic light scattering, as was written in the previous reviewer's reports.

The English language needs moderate editing.

Author Response

Thank you for your criticisms/comments/suggestions. I revised the whole introduction part. I made a mistake in the reference order because I added new references in previous revisions. The entire paper has been revised according to the new reference order. In addition, the prepared lubricant was analyzed by UV spectroscopy method due to the possibilities at my disposal. The result obtained was compared with the reference papers and the graph was added to the paper.