Improvement Efficiency and Emission Reduction in Used Cars for Developing Regions Using Gasoline–Bioethanol Blends

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The study demonstrates that low ethanol concentrations (E5 and E10) can be safely utilized in older vehicles without modifications, resulting in reduced pollutant emissions, improved thermal efficiency, and moderate performance trade-offs. These findings support the use of ethanol blends as a viable and sustainable fuel alternative during the transition to cleaner energy solutions.

General Recommendations

1. Improve transitions between sections to create a smoother flow.

2. Add a graphical abstract summarizing the study's key findings visually.

3. Discuss practical and economic aspects of ethanol adoption in older vehicles to enhance relevance.

Comments and Suggestions for Improvement

1. Title and Abstract: The title conveys the research topic well, but it could better highlight key findings such as emissions reductions and efficiency improvements. Rephrase the title to emphasize the environmental and performance benefits observed with ethanol blends. The abstract provides useful details but should clarify the practical implications and novelty of the results. Emphasize scalability for older vehicles and highlight ethanol's role in sustainability.

2. Introduction: The introduction sets a good context but is somewhat lengthy and lacks a focused research gap statement. I would suggest the authors to streamline the introduction by reducing redundancy and focusing on the need to test ethanol blends in unmodified older vehicles. Also, emphasize the relevance of findings for biofuel adoption, particularly in developing regions.

3. Materials and Methods: The methods section is well-structured but would benefit from additional details about testing consistency and calibration. Suggestions: (i) Explain the rationale for choosing specific RPM ranges and ethanol concentrations. (ii) Provide information about error margins, repeatability, and fuel composition variability. (iii) Clarify adjustments made to restore the vehicle to factory conditions and their potential impact on results.

4. Results and Discussion: The results section is comprehensive but could present data more clearly for easier interpretation. Suggestions: (i) Highlight key trends more explicitly, particularly reductions in emissions and efficiency gains.(ii) Use tables to summarize percentage changes in emissions and performance across blends and speeds. (iii) Improve figure captions by clearly explaining trends and observations.

5. Mechanistic Insights: The discussion of air-fuel ratios and combustion dynamics is technically sound but may be complex for non-specialist readers. Suggestions: (i) Simplify explanations of combustion process improvements from ethanol blending.(ii) Add flowcharts or diagrams to illustrate chemical and thermal processes involved.(iii) Discuss practical trade-offs, such as increased NOx emissions versus reduced CO and HC emissions.

6. Figures and Tables: Figures support the data well but need better formatting for readability. Suggestions: (i) Increase font sizes and line weights for clarity.(ii) Add labels and annotations to highlight important trends. (iii) Provide a summary table showing performance metrics and emission reductions for each blend.

7. Conclusions: The conclusions summarize findings effectively but could provide more specific recommendations for future research. Suggestions: (i) Suggest future studies on ethanol blends with higher concentrations or in different vehicle types. (ii) Highlight the potential for retrofitting older vehicles with ethanol-compatible systems. (iii) Discuss policy implications for promoting biofuels in urban transportation.

8. References: The references are relevant but could be updated with recent studies. Suggestions: (i) Verify formatting for consistency. (ii) Add recent research (last 2–3 years) on ethanol-gasoline blends and emissions. (iii) Cross-check in-text citations for alignment with the reference list.

9. Language and Style: The manuscript maintains formal language but occasionally uses complex sentences. Suggestions: (i) Simplify technical terms and break down lengthy sentences. (ii) Shorten paragraphs for better readability. (iii) Perform a final proofread to catch any grammatical or typographical errors.

Comments on the Quality of English Language

The manuscript maintains formal language but occasionally uses complex sentences.

Author Response

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Reviewer 2 Report

Comments and Suggestions for Authors

1.

In order to use any fuel, we must know its physicochemical properties. Tables must be presented for the initial fuels and for the mixtures used.

Density 15oC, g/ml

Kinematic Viscosity, (-20oC)mm2/s (cSt)

Humidity mg/kg

Total Acid Number (mg/g KOH)

Heat of Combustion, MJ/Kg

Flash Point (°C)

Distillation Residue (vol %)

Distillation Temperature 10% Recovery (°C)

 

2.

 

Special reference to the Flash Point (°C) of the mixtures.

 

3.

The production of bioethanol and the cost of production of the final mixtures must be mentioned

4.

The legislation provides for special procedures for mixing and transporting E10 gasoline as bioethanol dissolves easily in water and the presence of humitidy  in the gasoline-bioethanol mixture can lead to separation of the two substances. What is the humidity content of the of the fuel used?

5.

 Ethanol is also a solvent, it is capable of damaging hoses and insulating parts made of rubber or plastic. The engine should be checked for such damage.

Author Response

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Reviewer 3 Report

Comments and Suggestions for Authors

(1) Provide the advantages (highlights) and limitations of the research or methodology in the manuscript

(2) In fact, the author's methods and theories for data processing based on the experimental data obtained. What are the experimental methods used in the study and the applicability of these processing theories?

(3) In Figure 2, we can see that the change in rotational speed at low concentrations does not alter the parameters of Relative air/fuel ratio and Actual air/fuel ratio. However, when the speed exceeds 2500rpm, the change in speed will to some extent alter these two parameters. What is the reason for this?

(4) Figure 3 and 6 is not clear enough and requires a higher resolution image to replace it.

(5) The higher the carbon monoxide content in the exhaust, the less complete the combustion. For any type of gasoline ethanol mixture, the amount of CO is extremely high at low speeds, but extremely low at high speeds, lower than standard conditions. However, the analysis was conducted at three different speeds in the study, which does not provide good guidance for recommendations and optimization of driving habits.

Author Response

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Reviewer 4 Report

Comments and Suggestions for Authors

1: The research significance of the combustion gas emissions and performance evaluation of used cars in the abstract is not well reflected in the original article, which requires the author to add it in detail to the original article. In addition, key topic information such as greenhouse effect and human health in the keywords is not reflected, and the author needs to summarize and add it to the original article.

2: In section 2.1, regarding the construction of the test platform, the author needs to provide detailed instrument data indicators or threshold indicators, so that readers can more clearly analyze the precision of the test platform or the evaluation data of used cars. In addition, the author's relevant vehicle information for the used cars used in this study must also be disclosed in the article.

3: The underlying reasons why the low speeds of 1500rpm and 2500rpm in Figure 2 show exactly the same values ​​need to be analyzed in detail by the author and added to the original article. In addition, what is the basis for the safe operating range marked by the author in Figure 3? We can see from the safe operating range marked by the author in Figure 3 that the data is not very stable. Will this affect the author's judgment range?

4: Another sentence was added to express the "Crude oil quality also affects the difference in gas emissions of used cars"in the introduction section, It needs to be supported by some previous papers: ----The Carrying Behavior of Water-Based Fracturing Fluid in Shale Reservoir Fractures and Molecular Dynamics of Sand-Carrying Mechanism. -----A Numerical Investigation on Kick Control with Displacement Kill Method during Well Test in Deep-water Gas Reservoir: Case Study.

5: What are the possible reasons for the sudden and rapid increase in data at 3500rpm in Figure 4? What damages may the rapid increase in data cause to the exhaust emission system of used cars? What performance indicators can these data indicate for guiding the evaluation of combustion gas emissions of used cars? In addition, what are the possible reasons for the rapid drop in oil after 3500rpm?

6: What are the reasons for the completely different test evaluation times in Figure 6? The reviewer suggested that the authors fill in the same test evaluation times. In addition, the authors also need to revise the legend of Figure 6 because carbon dioxide and CO₂ are repeatedly described in the legend. Moreover, what is the reference basis for the standard maximum value marked in Figure 6?

Author Response

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Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Based on the answers given by authors the paper accepted for publication

Author Response

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Reviewer 4 Report

Comments and Suggestions for Authors

accepted

Author Response

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