Experimental Analysis of Engine Performance and Exhaust Pollutant on a Single-Cylinder Diesel Engine Operated Using Moringa Oleifera Biodiesel

Round 1

Reviewer 1 Report

This paper is amongst the excellent papers. It is coincide, novel and interesting.  The authors have successfully presented their work in a clear approach. The readability of the paper is also excellent. 

I only have minor comments; 

1- Line 41, define abbreviations before using them

2-The introduction is too long compared to the paper's length, please summarize and compare your contribution to those in the literature. 

3- Add a discussion section 

4- I think discussing the economic feasibility of producing your blend might be a very important point. Yet, I don't think it is mandatory, but it is worth mentioning it as future work, or at least rais the question.

5- The natural question now is what is the combustion characteristics of your blend. 

6- points 5 and 4 are examples of why you might need to add a discussion section

7-  At the moment ; It was found that MOB10 carried lower 42 BP (7.44%), BSFC (7.51%) and CO2 (7.7%). The MOB10 also reduced Smoke opacity (24%) and HC 43 (10.27%). As compared to diesel, MOB10 also increased CO (2.5%) and NOx (9%) emissions.

This essentially means that the suggested blends solve some problems but cause another, therefore, a trade of study shall be recommended as future work. 

This is another reason why a discussion section is needed. 

---------------------------------------------

Overall evaluation: minor correction. 

Good Luck.  

Author Response

This paper is amongst the excellent papers. It is coincide, novel and interesting. The authors have successfully presented their work in a clear approach. The readability of the paper is also excellent. I only have minor comments.

Thank you so much for the appreciation, and for your valuable recommendation on the submitted manuscript. As per your suggestions we have carefully read all the comments, recommendations, and suggestions, addressed cautiously in the manuscript.

In the following sections, you will find our responses to each of your comments and suggestions. We found the review comments very useful as we approached our revision, and the authors are grateful for the time and energy you expended on our behalf.

Comment 1:

Line 41, define abbreviations before using them.

Response:

Many thanks for reviewer’s kind suggestion. A new section of nomenclature has been added in the revised manuscript.

Comment 2:

The introduction is too long compared to the paper's length, please summarize and compare your contribution to those in the literature. 

Response:

Authors would like to say thanks to reviewer for kind suggestion. Authors have removed some irrelevant lines from the revised manuscript.

Comment 3:

Add a discussion section.

Response:

Many thanks for highlighting this important point in the manuscript. Authors have    added an additional paragraph at the end of the introduction section.

Comment 4:

I think discussing the economic feasibility of producing your blend might be a very important point. Yet, I don't think it is mandatory, but it is worth mentioning it as future work, or at least rais the question.

Response:

Many thanks for this kind suggestion, it is a little bit difficult for authors to add the economic feasibility at this stage. However, authors will incorporate these important points in future work.

Comment 5:

The natural question now is what is the combustion characteristics of your blend. 

Response:

Thanks for your concern regarding combustion characteristics of Moringa Oleifera biodiesel-diesel fuel blends. Unfortunately, combustion analyzer is not in working condition due to malfunctioning, so it is not possible for us to provide the combustion characteristics of fuel blends. Hopefully, in future work we will include combustion results in our upcoming research publications.  

Comment 6:

points 5 and 4 are examples of why you might need to add a discussion section

Response:

Many thanks to reviewer for this kind suggestion. Authors have added an additional discussion in the introduction which may attract the readers.

Comment 7:

At the moment; It was found that MOB10 carried lower 42 BP (7.44%), BSFC (7.51%) and CO_{2 (}7.7%). The MOB10 also reduced Smoke opacity (24%) and HC 43 (10.27%). As compared to diesel, MOB10 also increased CO (2.5%) and NOx (9%) emissions.

This essentially means that the suggested blends solve some problems but cause another, therefore, a trade of study shall be recommended as future work. This is another reason why a discussion section is needed. 

We agree with you, due to presence of oxygen atom in biodiesel shows a slight increase in NO_x emissions as compare to high-speed diesel. This is the main problem with the use of biodiesel at commercial level, the discussion about the formation of NO_x emissions is added in the revised manuscript as well as given below

“NOx emissions are influenced by the spray characteristics and oxygen content of the fuel and adiabatic flame temperature. Spray fuel characteristics refer to the size and mo-mentum of fuel droplets, degree of mixing between fuel droplets with air, penetration rate and evaporation, and radiant heat transfer rate”

The future work recommended is how to reduce the NO_x emissions using different fuel additives like different nanoparticles or alcoholic. 

Overall evaluation: minor correction. Good Luck.  

We have revised the Manuscript as per your suggestions and believe that the Article is much more intelligible now. the authors are extremely thankful, and appreciate the reviewer for the constructive, positive, and insightful comments to help us improve the manuscript.

Author Response File: Author Response.docx

Reviewer 2 Report

This is an interesting paper addressing an important issue. It can be considered for publication in Applied Sciences. However, I have the following comments that the authors should carefully implement in the revised manuscript before publication.

1) Introduction - The authors stressed the importance of developing new fuels to reduce pollutant emissions from diesel engines. However, in the revised Introduction, in order to give a more complete picture, they should better highlight, citing pertinent literature works, also the importance of developing - in parallel to new fuels and new injection strategies - highly performing after-treatment devices, i.e., Diesel Particulate Filters (DPFs) (see, e.g., AIChE Journal, Volume 64, Issue 5, 2018, Pages 1714-1722; AIChE Journal, Volume 63, Issue 8, 2017, Pages 3442-3449).

2) Introduction - The connection between the aim of the work and the literature gaps should be described (at the end of the section “Introduction”).

3) Results - In the discussion of the results, more criticism is needed, as this is a research article and not a technical report.

4) Conclusions - The authors should highlight the practical impact of the results obtained in this work. They should also give an outlook on future research work.

I’m willing to review the revised manuscript.

Author Response

This is an interesting paper addressing an important issue. It can be considered for publication in Applied Sciences. However, I have the following comments that the authors should carefully implement in the revised manuscript before publication.

In the following sections, you will find our responses to each of your comments and suggestions. We found the review comments very useful as we approached our revision, and the authors are grateful for the time and energy you expended on our behalf.

Comment 1:

Introduction - The authors stressed the importance of developing new fuels to reduce pollutant emissions from diesel engines. However, in the revised Introduction, in order to give a more complete picture, they should better highlight, citing pertinent literature works, also the importance of developing - in parallel to new fuels and new injection strategies - highly performing after-treatment devices, i.e., Diesel Particulate Filters (DPFs) (see, e.g., AIChE Journal, Volume 64, Issue 5, 2018, Pages 1714-1722; AIChE Journal, Volume 63, Issue 8, 2017, Pages 3442-3449).

Response:

Many thanks for your suggestion regarding addition of previous literature to strengthen the introduction section. Suggestions are addressed in revised manuscript.     

Comment 2:

Introduction - The connection between the aim of the work and the literature gaps should be described (at the end of the section “Introduction”).

Response:

Authors would like to say thanks to reviewer for kind suggestion, Authors have added an additional paragraph at the end of the revised manuscript which make a connection with aim of the work with existing literature.

Comment 3:

Results - In the discussion of the results, more criticism is needed, as this is a research article and not a technical report.

Response:

Many thanks for reviewer’s kind suggestion. Authors have added important logics which explain and verify the obtained results.

Comment 4:

Conclusions - The authors should highlight the practical impact of the results obtained in this work. They should also give an outlook on future research work.

Response: 

As per your suggestion, we have provided the future recommendations: The NO_x emissions observed slightly increased in case of combustion of biodiesel blends as compare to conventional diesel. The researchers can pursue this work using different fuel additives like nanoparticles or alcohols to reduce the NO_x emissions. 

We have revised the Manuscript as per your suggestions and believe that the Article is much more intelligible now. the authors are extremely thankful, and appreciate the reviewer for the constructive, positive, and insightful comments to help us improve the manuscript.

Author Response File: Author Response.docx

Reviewer 3 Report

The manuscript presents experimental results on the engine performance achieved with Moringa oleifera biodiesel. The results are compared to the data of the commercial diesel, and they seem promising.

Therefore, this manuscript constitutes the starting point for an application on a larger scale. However, it needs some changes and improvements, and major revisions are requested.

Moreover, few comments on the results are given and a scientific discussion is missing: for this reason, the manuscript can be considered as a COMMUNICATION.

SCIENTIFIC ISSUES

1. The section INTRODUCTION must be improved since the current state shows the status of the art but the study aims are not given. Moreover, the Authors are requested to expose the results from other studies in an orderly (in the present version they appear a bit confused).
2. MATERIALS AND METHODS: subchapters for the definition of BTE and SMOKE OPACITY must be added.
3. Table 1: it seems impossible that the injection volume into the gaschromatograph is equal to 1 liter (probably there is a typing error).
4. Table 2: the parameter units must be given (for example, molecular mass (g/mol), and so on).
5. Sub-chapter 2.4 ENGINE SETUP: the Authors must clarify if each run has been repeated, or if each experimental point is the result of a single run.
6. Row 258: the “previous researchers” must be clarified by references.
7. Figure 4: the red line is questionable its maximum is not supported by experimental results. The spline could be inadequate and not representative, neither about the maximum value (the point could be higher) nor for the abscissa of this point (it could be at a different engine speed). The Authors must justify the given plot.
8. The same for Figure 6.
9. Rows 283-284: the sentence is questionable since it is obvious that a low quantity of oxygen is responsible for a lower quantity of carbon dioxide. The performance comparison must be reasonable, to say keeping constant at least one parameter. Otherwise, it does not constitute a comparison, but simply a comment on one result.

EDITORIAL ISSUES

1. The manuscript makes use of a huge number of acronyms, very often not specified when they appear for the first time. Each of them must be explained when it is used for the first time in the text. This is their list:

- ABSTRACT: B10, B20, MOB10, MOB, BSFC, HC

- Row 77: MOB

- Row 80: SCDE

- Row 96: CI

- Row 104: B25, B50, B75

- Row 108: BTE, EGT

- Row 109: SOME

- Row 113: COME

- Row 136: B100

- Row 156: DW

- Row 158: MOME

- Row 164: FAC

- Row 182: CFPP

- Row 228: HHV

2. Table 3 has the title in the wrong position.
3. Row 187: the equation must be written correctly (some brackets seem useless or in surplus) and then numbered.
4. Row 321: one literature reference cannot be simply recalled by a number (the Authors must follow the editorial rules given by the journal).

Author Response

Reviewer #3:

The manuscript presents experimental results on the engine performance achieved with Moringa oleifera biodiesel. The results are compared to the data of the commercial diesel, and they seem promising. Therefore, this manuscript constitutes the starting point for an application on a larger scale. However, it needs some changes and improvements, and major revisions are requested. Moreover, few comments on the results are given and a scientific discussion is missing, for this reason, the manuscript can be considered as a Communication.

Thank you so much for the appreciation, and for your valuable recommendation on the submitted manuscript. As per your suggestions we have carefully read all the comments, recommendations, and suggestions, addressed cautiously in the manuscript.

Scientific Comments:

Comment 1:

The section INTRODUCTION must be improved since the current state shows the status of the art but the study aims are not given. Moreover, the Authors are requested to expose the results from other studies in an orderly (in the present version they appear a bit confused).

Response: 

Many thanks to reviewer for this kind suggestion, the additional paragraphs have been added in the revised manuscript which may attract the reader’s attention. Additionally, the irrelevant data has been removed. The last paragraph describes the aim of the study.

Comment 2:

MATERIALS AND METHODS: subchapters for the definition of BTE and SMOKE OPACITY must be added.

Response: 

Many thanks for highlighting this issue in manuscript. Authors have added needful definitions of BTE and SMOKE OPACITY in the revised manuscript.

Comment 3:

Table 1: it seems impossible that the injection volume into the gas chromatograph is equal to 1 liter (probably there is a typing error).

Response: 

Many thanks for your observation. It is 1mL instead of 1L. Change is incorporated in revised manuscript.

Comment 4:

Table 2: the parameter units must be given (for example, molecular mass (g/mol), and so on).

Response: 

Many thanks for highlighting this issue in manuscript. Units of molecular mass and composition of MOME have been added in the revised manuscript.

Comment 5:

Sub-chapter 2.4 ENGINE SETUP: the Authors must clarify if each run has been repeated, or if each experimental point is the result of a single run.

Response: 

Thanks for your concern regrading engine setup. All experiments are performed in triplicates to ensure the accuracy of results.

Comment 6:

Row 258: the “previous researchers” must be clarified by references.

Response: 

Thanks for your comment. Needful references are added in revised manuscript to incorporate your suggestion.

Comment 7:

Figure 4: the red line is questionable its maximum is not supported by experimental results. The spline could be inadequate and not representative, neither about the maximum value (the point could be higher) nor for the abscissa of this point (it could be at a different engine speed). The Authors must justify the given plot. The same for Figure 6.

Response: 

Thank you very much for pointing out the correction, as per your recommendation we checked the curve for MOB10 and MOB20 and modified the curve using averaged readings.

Comment 8:

Rows 283-284: the sentence is questionable since it is obvious that a low quantity of oxygen is responsible for a lower quantity of carbon dioxide. The performance comparison must be reasonable, to say keeping constant at least one parameter. Otherwise, it does not constitute a comparison, but simply a comment on one result.

Response: 

Thanks for your comment. Presence of higher amount of oxygen content in fuel blends increased the conversion of CO to CO₂ which resulted in lower CO emissions. Similar result was reported by other researchers.

EDITORIAL ISSUES

Comment 1:

The manuscript makes use of a huge number of acronyms, very often not specified when they appear for the first time. Each of them must be explained when it is used for the first time in the text. This is their list:

Response: 

Many thanks for highlighting this issue. Authors have inserted a new section of Nomenclature which may be helpful for readers to understand the manuscript

- ABSTRACT: B10, B20, MOB10, MOB, BSFC, HC

- Row 77: MOB

- Row 80: SCDE

- Row 96: CI

- Row 104: B25, B50, B75

- Row 108: BTE, EGT

- Row 109: SOME

- Row 113: COME

- Row 136: B100

- Row 156: DW

- Row 158: MOME

- Row 164: FAC

- Row 182: CFPP

- Row 228: HHV

Comment 2:

Table 3 has the title in the wrong position.

Response: 

Many thanks for this kind suggestion, Table 3 is adjusted at the end of the paragraph

Comment 3:

Row 187: the equation must be written correctly (some brackets seem useless or in surplus) and then numbered.

Response: 

Authors would be thankful to reviewer’s for highlighting this issue as this issue may cause trouble for readers. However, this problem is resolved in the revised manuscript.

Comment 4:

Row 321: one literature reference cannot be simply recalled by a number (the Authors must follow the editorial rules given by the journal).

Response: 

Thanks for your suggestion. MDPI endnote output style opted for revised manuscript for all references.

Author Response File: Author Response.docx

Reviewer 4 Report

The authors have carried out extensive research on the comparison of NPs on biodiesel. Before acceptance of the work the authors need to respond to the following comments:

1. The author has written over 200 words in the abstract and yet has only described the context but not the results of their work and the implications such as, CO, HC and NOx.
2. The authors did not cover the relevant points in the Abstract background/context: 1. Research problem/aim - the gap they plan to fill, 2. Methodology, 3. Novelty.
3. Please add the full form of the abbreviated words the first they are used in the Abstract.
4. The author has not related the background information to the objective of the paper in the Introduction section.
5. The Introduction occupies too high a proportion of the entire paper and contains too many general statements that are already widely known.
6. Please use simple words for better understanding, not complex synonyms.
7. The methods and introduction section refer to the similar works for different biodiesel and alcohols
8. Please cite the Figures if they are adopted from previous studies.
9. Please provide the characterization results if possible for better understanding
10. Which equipment was used for ultrasonication of the mixture?

Author Response

The authors have carried out extensive research on the comparison of NPs on biodiesel. Before acceptance of the work the authors need to respond to the following comments:

Thank you so much for the appreciation, and for your valuable recommendation on the submitted manuscript. As per your suggestions we have carefully read all the comments, recommendations, and suggestions, addressed cautiously in the manuscript.

Comment 1:

The author has written over 200 words in the abstract and yet has only described the context but not the results of their work and the implications such as, CO, HC and NOx.

Response: 

As per your suggestion we have inserted all the results in the abstract.

Comment 2:

The authors did not cover the relevant points in the Abstract background/context: 1. Research problem/aim - the gap they plan to fill, 2. Methodology, 3. Novelty.

Response: 

We have highlighted the 1. Research problem/aim - the gap they plan to fill, 2. Methodology, 3. Novelty in the abstract and introduction section.

Comment 3:

Please add the full form of the abbreviated words the first they are used in the Abstract.

Response: 

We have added Nomenclature table and explained the words the first time it is used in the abstract.

Comment 4:

The author has not related the background information to the objective of the paper in the Introduction section.

Response: 

We have adequately explained the background work of the research work and also mentioned novelty at the end of the introduction section.

Comment 5:

The Introduction occupies too high a proportion of the entire paper and contains too many general statements that are already widely known.

Response: 

As per your suggestion we have reduced the introduction section and added only the important information required in this study.

Comment 6:

Please use simple words for better understanding, not complex synonyms.

Response: 

As per your suggestion we have used simple words in the article.

Comment 7:

The methods and introduction section refer to the similar works for different biodiesel and alcohols.

Response: 

We have differentiated the methods and introduction section in the revised manuscript.

Comment 8:

Please cite the Figures if they are adopted from previous studies.

Response: 

Thank you for the recommendation.

Comment 9:

Please provide the characterization results if possible for better understanding.

Response: 

Due to ongoing pandemic, the university and labs are closed. We were unable to determine the characterization tests.

Comment 10:

Which equipment was used for ultrasonication of the mixture?

Response: 

Thank you for the recommendation, in the current study we used transesterification reaction and ultrasonication process was not utilized.

We have revised the Manuscript as per your suggestions and believe that the Article is much more intelligible now. the authors are extremely thankful, and appreciate the reviewer for the constructive, positive, and insightful comments to help us improve the manuscript.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The authors have addressed my comments in a satisfactory manner. Overall, the manuscript has been improved after revisions. Therefore, it can be accepted for publication in Applied Sciences.

Author Response

Thank you so much for the appreciation, and for your valuable recommendation on the submitted manuscript. As per your suggestions we have carefully read all the comments, recommendations, and suggestions, addressed cautiously in the manuscript. We found the review comments very useful as we approached our revision, and the authors are grateful for the time and energy you expended on our behalf.

Author Response File: Author Response.docx

Reviewer 3 Report

The manuscript has been improved, accepting comments and requests. However, some points are still pending.

Reply to Comment 2:

MATERIALS AND METHODS: subchapters for the definition of BTE and SMOKE OPACITY must be added. This kind of definitions are part of the MATERIALS AND METHODS, not of the RESULTS.

The Authors are kindly requested to add the sub-chapters, moving from the results.

Reply to Comment 5:

The Authors are kindly requested to add the information that all the experiments were performed in triplicates (sub-chapter 2.4 ENGINE SET-UP). This information is rather relevant for the manuscript quality.

Reply to Comment 7:

If Figures 4 and 6 show averaged data, the information must be declared into the manuscript, to support the modeling.

Reply to Comment 8:

The comment done by the Authors must be introduced into the manuscript.

Author Response

Reviewer #3:

The manuscript has been improved, accepting comments and requests. However, some points are still pending.

In the following sections, you will find our responses to each of your comments and suggestions. We found the review comments very useful as we approached our revision, and the authors are grateful for the time and energy you expended on our behalf.

Comment 1:

Reply to Comment 2: MATERIALS AND METHODS: subchapters for the definition of BTE and SMOKE OPACITY must be added. This kind of definitions are part of the MATERIALS AND METHODS, not of the RESULTS. The Authors are kindly requested to add the sub-chapters, moving from the results.

Response: Many thanks for this kind suggestion, subchapters for the definitions of BTE and smoke opacity have been added in material and methods section.

Comment 2:

The Authors are kindly requested to add the information that all the experiments were performed in triplicates (sub-chapter 2.4 ENGINE SET-UP). This information is rather relevant for the manuscript quality.

Response: Many Thanks for your comment. Experiments were performed in triplicates. Each blend was run three times for obtaining the accurate results. Each experiment took almost 20 to 30 minutes for single blend. Single run gave almost 5 to 6 values at selective rpms. For graphs average values were taken for the current study.  

Comment 4:

Reply to comment 7: If Figures 4 and 6 show averaged data, the information must be declared into the manuscript, to support the modeling.

Response: Thank you for the suggestion, we have introduced the averaged data in the text and highlighted.

Comment 5:

Reply to Comment 8: The comment done by the Authors must be introduced into the manuscript.

Response:  Thank you very much, as per your recommendation we have introduced the corrections in the manuscript.

We have revised the Manuscript as per your suggestions and believe that the Article is much more intelligible now. the authors are extremely thankful, and appreciate the reviewer for the constructive, positive, and insightful comments to help us improve the manuscript.

Author Response File: Author Response.docx

Reviewer 4 Report

The next version of the paper has been significantly improved. I have no further comments and the paper can be accepted for publication in the journal.

Author Response

Thank you so much for the appreciation, and for your valuable recommendation on the submitted manuscript. As per your suggestions we have carefully read all the comments, recommendations, and suggestions, addressed cautiously in the manuscript. We found the review comments very useful as we approached our revision, and the authors are grateful for the time and energy you expended on our behalf.

Author Response File: Author Response.docx