An Experimental Study of Operating Range, Combustion and Emission Characteristics in an RCCI Engine Fueled with Iso-Propanol/n-Heptane
Round 1
Reviewer 1 Report
The main suggestions are listed below: (1) The first time an acronym appears in the manuscript it should be defined, such as NOx, HC and so on. (2) In line 140, the dynamometer power at 4000 rpm is 10kW. However, in table 1, the maximum engine power is 12HP at 3000 rpm. So whether the dynamometer power is enough at 3000 rpm or other speed? (3) As we know that, PM emission is very important in diesel engine. But the author just showed the HC, CO and NO emission characteristics in the manuscript. I think that is insufficient for the emissions characteristics of the iso-propanol and n-heptane blends. The comparisons of PM should be added to the article. (4) In line 185, “In the first case study, ….. IAT of 30°C and….”, While in Table 4, the Intake air temperature of case-1 is 50°C. The author should check that very carefully. (5) Why the intake air temperature is so high which is reached 70°C？ Is that reasonable? (6) It is better if the author give some specific suggestions for the application of iso-propanol and n-heptane in engines. (7) I would like to recommend the reference for you, you can decide yourself if it is useful: Exploration on the emissions and catalytic reactors interactions of a non-road diesel engine through experiment and system level simulation. Fuel 2023; 342: 127746. https://doi.org/10.1016/j.fuel.2023.127746.Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
I have carefully read the manuscript sustainability-2470561 entitled “An experimental study of operating range, combustion and emission characteristics in an RCCI engine fueled with iso-propanol/n-heptane “. In this work, the influence of different parameters (the premixed ratio (PR) and intake air temperature (IAT)) on the operating range, combustion characteristics, and emissions in a reactivity controlled compression ignition (RCCI) engine fueled with iso-propanol/n-heptane was experimentally investigated. The experiments were conducted for two different case studies: In the first case, the experiments were performed at 50°C intake air temperature and three different premix ratios (PR25, PR50, PR75). In the second case, experiments were conducted at three different intake air temperatures (30°C, 50°C, 70°C) with PR50. Several results were presented and thoroughly discussed. The manuscript is scientifically sound, add to the bulk knowledge, and well written/presented, thanks to the authors. I have the following comments and suggestions:
1. Title and abstract are representative. The introduction section is reach, relevant, and up-to date. I am only suggesting increasing the citation of references while discussing the results. Additionally, would you please check citing references from which you get the equations?
2. The English technical writing is good but needs more polishing. Would you please check/revise? As examples P1 L14: “ … were experimentally investigated. In the …”, P2 L81: “ … to achieve low emissions over a …”, P3 L87: “In another study …”, P8 L269: “ … are shown in Figures 3 and 4.”, P14 L370: “ Figures 10 and 11 display …”
3. Would you please check the consistency in all the (superscripts/subscripts), especially in units?
4. Would you please check the consistency in using (NOx) and (NO)? I do suggest using (NOx). Also, would you please check consistency in the subscript in (NOx)?
5. Would you please check consistency in using (italic format)? L188 and L245
6. P6 L185: Would you please check that you are using here IAT=30°C, which is not the one you used in the experiments at different premix ratios (PR25, PR50, PR75)?
7. P7 L223: Would you please check that the symbol (dQw/dθ) is not existed in the equations?
The English technical writing is good but needs more polishing.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
At first glance it seems like a robust research. There are some missing points in the paper design. For instance, is important to state the paper objectives. At least, these objectives has to be declared in the first part of the article. Then, is vital to built a paper outline and explain the article workflow, as well. In the same time, please detail if the experimental setup is the author approach (or vision) and is based on.....?
You proposed two case studies but for the second case study, when you conducted experiments for three different intake air temperatures, you generated much more findings (in the case for the temperatures at the extremes of the range - 30°C and 70°C- ) than for the first case study. By forcing or speculating on this approach these things can be obtained similarly if we expand the extreme values (for instance 25°C and 75°C)?
In the section 2 you inserted three relationships. What was the basis for choosing these relationships? Please offer the sources for these equations. Also explain more about the algorithm developed in the MATLAB program (advantages, utility etc.).
In order to get a comprehensive picture of your research, you have to declare the limitations in your approach and in your experimental setup.
Also, based on the literature review and comparative studies can you describe in which situations these different intake air temperatures (30°C, 50°C, 70°C) could be reached in practice ("in reality")?
Finally, I want to get from you info about theoretical implications related to your research, and practical implications of your approach, as well.
Yes, it will be necessary to generate a proofreading round.
Author Response
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Author Response File: Author Response.pdf
Reviewer 4 Report
Detailed comments:
1. The English of the text should be checked – minor mistakes, errors
2. Please eliminate multiple references. After that, please check the manuscript thoroughly and eliminate ALL the lumps in the manuscript. This should be done by characterizing each reference individually and by mentioning 1 or 2 phrases per reference to show how it is different from the others and why it deserves mentioning. Multiple references are of no use for a reader and can substitute even a kind of plagiarism, as sometimes authors are using them without proper studies of all references used. In the case, each reference should be justified by it is used and at least short assessment provided.
3. At lines 41, 42, authors write: “In particular, simultaneous reduction of these emissions is not possible without expensive after-combustion techniques” – example of combustion techniques must be indicated More information about fabrication of membrane must be included - all operational conditions must be indicated, amount, concentration of reagent, time, speed rotation, value for “constant stirring”, value for room temperature, dimension of obtained membrane, thickness. Also, more information about preparation method of obtained membrane.
4. At page 4, the values for low and high pressure must be indicated
5. At lines 277, 278, authors write: “The less n-heptane fuel is contained in the mixture, the less amount of iso-propanol fuel is expected to combust because of the lower number of auto-ignition points.” – the value for amount of n-heptane, iso-propanol, and lower number of points, must be indicated
6. At lines 281, 282, authors write: “It can also be stated that the start of combustion is retarded as the alcohol compositions increase in the chemical structure of the fuel mixture.” – what means increase? The value must be indicated
7. At lines 284, 285, “..due to the increase in low reactivity fuel” – the value for reactivity fuel must be included
8. At line 383, “…resulting in shorter combustion periods” – the periods must be indicated
9. At lines 404, 405, “…The minimum NO emission” – the value must be indicated. Also, at line 406, “lowest NO emission values”
10. At line 413, “…due to the low temperature” – the value must be indicated
11. For all abbreviations or notation indicate the complete name
12. Comparison between the obtained results and measured in this study with other reported studies should be done and included for more clarity (indicate values not just number of reference).
Minor errors, mistake
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
Dear Author,
I am not agree at all with your way to respond to some issues. Please pay attention to all my comments. My questions are not looking answers for my personal interest. I asked things because there are missing within paper. Is not a discussion between me and you. Is a way to respond to similar questions addressed to you by potential readers. It is not a personal curiosity but a broad professional interest. I expected that the mentioned clarifications would be found in the paper.
Please go through each existing observation from my previous review and respond to it, including the answers within the article. The responses are partially done and there are related only to some issues!
Just a small example. You refer or claim in two of your responses a title which is not included in the paper and in the references list. And the example can continue. Please pay attention to all details and requests.
Before English checks, still remains work to do for the paper.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 3
Reviewer 3 Report
Please make a final proofreading round!
Check again the spelling and grammar.
Author Response
Dear Reviewer,
Thank you for your evaluation and valuable criticism.
A final revision was completed and some spelling and grammatical errors were corrected.
All revisions are clearly highlighted using the "Track Changes" function in Microsoft Word so that they are easily visible to editors and reviewers.
Yours sincerely,
Dr. Serdar Halis
