Impact of Hydrogen Peroxide Concentration on Manganese Oxide and Platinum Catalyst Bed Performance

Round 1

Reviewer 1 Report

Thank you very much for submitting this manuscript. I am very sorry that the review took me longer than I initially anticipated.

The topic is very relevant to the field and subject of latest research. I would be happy to see the manuscript finally published.

The introduction is good and concise. The description of the methology is sufficient and allows to comprehend the approach and to reproduce and independently verify the results. I have to nag that the origin of theoretical c* and adiabatic decomposition temperature is not given. Also some less common/ uncommon nomenclature is used which is not properly explained and also somewhat inconsistent. Eq. 1 must be checked as I think there is an error in it (or at least the symbols need to be explained).

English language and style is quite good. Anyhow, I found a few typos or odd wording.

In conclusion, this is a very good paper publishable after only a few checks/ corrections.

 

Detailed remarks:

Figure 1 a): y axis might be normalized?

Figure 1 b): solid (fluid temperature??) and dashed (wall temperature?) are not explained. Markings "I" and "II" are not explained.

L. 70 "µc*": I am confused ... shouldn't this be η_c* (eta with subscript c*)? If not, please clarify the definition you are using.

Table 1: How were the theoretical c* and adiabatic temperature determined? Something like CEA or any other tool?

Eq. 1: This equation introduces several (unexplained) symbols and seems to even mix them up (i.e. k and kappa?). R is universal gas constant, I guess. But what is "g" in this case? I would expect something like kappa*R/M*T_c with M being molar mass. Also I think the term below the fraction line was mixed up i.e. the formula I expect is sqrt((R*T_c)/(M*kappa) * (2/kappa+1)^((kappa+1)/(kappa-1))). Anyhow, the use of this formula also incorporates some issues i.e. how were - apart of T_c - kappa and the mixture specific gas constant determined?

L. 113/115/118, and L. 120 "µC*", see also remark on line 70: Inconsistent use of c* and C*. The c* (or C*) should be IMHO a subscript anyway.

L. 194 "µc*"

L. 227 and 231 "µc*", but L. 232 and 235 "µC*"

L. 50 wording: "characterize" -> "are characterized"

L. 92/95 "ƴ-alumina": I guess this is "gamma aluminum"? It might be an issue with the font but I think the symbol/sign is not a small letter gamma.

L. 141/142 "50 mm": Bad line break; usually this can easily be avoided by using a non-breaking space (CTRL+SHIFT+SPACE in Word) between numeral and symbol.

Table 2 "kg/s/m2": "kg/s/m²"

L. 203/204 "781 K": Bad line break

L. 215 typo (I guess): "low-pressure" --> "low pressure"

L. 241 wording: "further" --> "further downstream"

L. 282 typo: "Confrence" -> "Conference" 

Author Response

Dear Reviewer,

 

We would like to express our sincere gratitude for your valuable and insightful comments. Taking into consideration your feedback we have made the following revisions to the manuscript:

 

Comment 1:

I have to nag that the origin of theoretical c* and adiabatic decomposition temperature is not given.

Table 1: How were the theoretical c* and adiabatic temperature determined? Something like CEA or any other tool?

Answer 1:

Based on your comments and suggestion from another Reviewer, we corrected the subsection concerning the calculation of thermodynamic parameters of the HTP decomposition products.

Comment 2:

Also some less common/ uncommon nomenclature is used which is not properly explained and also somewhat inconsistent

Answer 2:

We have taken extra care to provide a more detailed explanation of the literature sources referenced in the manuscript.

Comment 3:

Eq. 1 must be checked as I think there is an error in it (or at least the symbols need to be explained).

Eq. 1: This equation introduces several (unexplained) symbols and seems to even mix them up (i.e. k and kappa?). R is universal gas constant, I guess. But what is "g" in this case? I would expect something like kappa*R/M*T_c with M being molar mass. Also I think the term below the fraction line was mixed up i.e. the formula I expect is sqrt((R*T_c)/(M*kappa) * (2/kappa+1)^((kappa+1)/(kappa-1))). Anyhow, the use of this formula also incorporates some issues i.e. how were - apart of T_c - kappa and the mixture specific gas constant determined?

Answer 3:

We acknowledge the error in Equation 1, and have provided a corrected version. We have also included additional explanations and symbols to facilitate easier identification and understanding.

Comment 4:

English language and style is quite good. Anyhow, I found a few typos or odd wording.

1. 50 wording: "characterize" -> "are characterized"

Table 2 "kg/s/m2": "kg/s/m²"

1. 215 typo (I guess): "low-pressure" --> "low pressure"
2. 241 wording: "further" --> "further downstream"
3. 282 typo: "Confrence" -> "Conference"

Answer 4:

We have thoroughly reviewed the manuscript for any linguistic errors, typos, and formatting issues.

Comment 5:

Figure 1 a): y axis might be normalized?

Figure 1 b): solid (fluid temperature??) and dashed (wall temperature?) are not explained. Markings "I" and "II" are not explained.

Answer 5:

We have incorporated a textual description of the content in Figure 1, including the intriguing phenomena of water evaporation followed by hydrogen peroxide downstream, resulting in a step-like graph. Unfortunately, due to time constraints and difficulties in obtaining copyright permissions for non-open access manuscripts or resources, the figure had to be removed.

Comment 6:

1. 70 "µc*": I am confused ... shouldn't this be η_c* (eta with subscript c*)? If not, please clarify the definition you are using.
2. 113/115/118, and L. 120 "µC*", see also remark on line 70: Inconsistent use of c* and C*. The c* (or C*) should be IMHO a subscript anyway.
3. 194 "µc*"
4. 227 and 231 "µc*", but L. 232 and 235 "µC*"

Answer 6:

We corrected c* and normalize it in all manuscript. The symbol for the efficiency of c*, has been rectified. There was an error in the Greek letter representation, which has now been corrected. Additionally, we have ensured consistency in its usage throughout the entire article.

Comment 7:

1. 92/95 "ƴ-alumina": I guess this is "gamma aluminum"? It might be an issue with the font but I think the symbol/sign is not a small letter gamma.

Answer 7:

We corrected Greek letter in gamma-alumina.

Comment 8:

1. 141/142 "50 mm": Bad line break; usually this can easily be avoided by using a non-breaking space (CTRL+SHIFT+SPACE in Word) between numeral and symbol.
2. 203/204 "781 K": Bad line break

Answer 8:

All bad break lines corrected.

 

Once again, we extend our sincere appreciation for your valuable input, which has significantly enhanced the quality of our work.

 

With kind regards,

The Authors

 

Reviewer 2 Report

Thank you for sending me the manuscript “Impact of hydrogen peroxide concentration on the manganese oxides and platinum catalyst bed performance” for revision. The Reviewer has the following observations.

 

1. Line 26. The information is not recent. In the Reviewer’s opinion, the authors exaggerated using seven references to state, "This propellant used in the 1960’s in propulsion was usually concentrated up to approximately 80%.” The Reviewer suggests decreasing the number of citations in this sentence, keeping one or two of the most important ones. Moreover, the Reviewer offers to highlight the objectives and identify gaps in previous studies to motivate the current research.

2. Line 89-103 2.1. The object of testing is not clearly specified. The Reviewer suggests adding technical parameters which describe the Platinum-based and Manganese catalysts and how exactly they were characterized. The significance of figs 2 and 3 is not clear. The Reviewer did not understand if the change of color in fig 3 has some meaning. Were the images calibrated?

3. Line 116. Please specify the values for k and R, and cite the calculation method of these parameters.

4. Line 248-249. The Reviewer suggests removing information about the total amount of propellants and catalysts consumed during the test since it does not impact the manuscript's results.

5. Line 246-262. The Reviewer suggests highlighting the new finding in the current research concerning the previously published works in hydrogen peroxide decomposition in monopropellant engines.

Author Response

Dear Reviewer,

 

The Authors would like to thank you for your valuable and accurate comments.

Comment 1:

Line 26. The information is not recent. In the Reviewer’s opinion, the authors exaggerated using seven references to state, "This propellant used in the 1960’s in propulsion was usually concentrated up to approximately 80%.” The Reviewer suggests decreasing the number of citations in this sentence, keeping one or two of the most important ones. Moreover, the Reviewer offers to highlight the objectives and identify gaps in previous studies to motivate the current research.

Answer 1:

We modified the introduction, reducing the number of citations for the statement on 80% hydrogen peroxide. The objectives of the research and motivation have also been highlighted, taking into consideration the existing findings.

Comment 2:

Line 89-103 2.1. The object of testing is not clearly specified. The Reviewer suggests adding technical parameters which describe the Platinum-based and Manganese catalysts and how exactly they were characterized. The significance of figs 2 and 3 is not clear. The Reviewer did not understand if the change of colour in fig 3 has some meaning. Were the images calibrated?

Answer 2:

The corrected the section concerning the object of testing, adding information on the characterization methods applied to the catalysts and providing a table with basic parameters. The question of photographs and differences in colours and shades have been also explained.

Comment 3:

Line 116. Please specify the values for k and R, and cite the calculation method of these parameters.

Answer 3:

Based on your comments and suggestion from another Reviewer, we corrected the subsection concerning the calculation of thermodynamic parameters of the HTP decomposition products.

Comment 4:

Line 248-249. The Reviewer suggests removing information about the total amount of propellants and catalysts consumed during the test since it does not impact the manuscript's results.

Answer 4:

We removed irrelevant sentences from the Conclusions and highlighted the meaning of our research.

Comment 5:

Line 246-262. The Reviewer suggests highlighting the new finding in the current research concerning the previously published works in hydrogen peroxide decomposition in monopropellant engines.

Answer 5:

We also highlighted the new findings on the background of the previous research.

 

With kind regards,

The Authors

Reviewer 3 Report

     In this study, the authors experimentally investigate how the concentration of hydrogen peroxide affects the efficiency of decomposition using two different catalysts, platinum and manganese oxide. They evaluate the efficiency using characteristic exhaust velocity (c* efficiency).     Although the c* efficiency is an appropriate indicator in assessing the degree of completion of a chemical reaction, it also includes the heat loss effect. Another concern is that it is difficult to determine which conditions must be aligned to compare the two types of catalysts. In the present study, the geometry of the ceramic supports is different, and so is the surface area where the heterogeneous reaction occurs. Accordingly, deriving academic findings with versatility by experiments using a specific reaction condition is challenging. For example, suppose the authors examine the relationship between c* efficiency and L* under each combination of the H2O2 concentration and the catalyst. In that case, they can obtain the maximum c* efficiency and L* at that time. The L* giving the maximum c* efficiency corresponds to the characteristic time of the chemical reaction under those conditions, and the maximum c* efficiency gives the limiting value of efficiency under those conditions.     Hydrogen peroxide has a long history as a rocket propellant, and many researchers have studied it. What kind of research they have done and what novelty exists in this study must be explained. Since the author has performed no error analysis, the reader cannot determine the data's reliability. In conclusion, the reviewer does not recommend publishing this paper in an academic journal.

Some sentences are difficult to understand. Minor editing of English is necessary.

Author Response

Dear Reviewer,

 

The authors would like to thank you for your time and effort in reviewing of our manuscript.

Comment 1:

In this study, the authors experimentally investigate how the concentration of hydrogen peroxide affects the efficiency of decomposition using two different catalysts, platinum and manganese oxide. They evaluate the efficiency using characteristic exhaust velocity (c* efficiency).     Although the c* efficiency is an appropriate indicator in assessing the degree of completion of a chemical reaction, it also includes the heat loss effect. Another concern is that it is difficult to determine which conditions must be aligned to compare the two types of catalysts. In the present study, the geometry of the ceramic supports is different, and so is the surface area where the heterogeneous reaction occurs. Accordingly, deriving academic findings with versatility by experiments using a specific reaction condition is challenging. For example, suppose the authors examine the relationship between c* efficiency and L* under each combination of the H2O2 concentration and the catalyst. In that case, they can obtain the maximum c* efficiency and L* at that time. The L* giving the maximum c* efficiency corresponds to the characteristic time of the chemical reaction under those conditions, and the maximum c* efficiency gives the limiting value of efficiency under those conditions.  Hydrogen peroxide has a long history as a rocket propellant, and many researchers have studied it. What kind of research they have done and what novelty exists in this study must be explained. Since the author has performed no error analysis, the reader cannot determine the data's reliability. In conclusion, the reviewer does not recommend publishing this paper in an academic journal.

Answer 1:

Please notice that the main objective of the research was to investigate  the effect of hydrogen peroxide concentration on performance of a thruster-like catalyst bed, with two different catalysts. In these tests we used a chamber in which the diameter and length of the chamber and the throat diameter were constant. The authors are aware that the length of the catalytic bed i.e. L* can have a significant impact on the overall efficiency of characteristic velocity. Such research will be carried out in the next stage, using one of the catalysts presented in the article.

 

We encourage the Reviewer to read our paper in the latest version, as we introduced major modifications. The motivation for our research is currently well-described, also in the background of other findings, available in literature.

 

With kind regards,

The Authors

Round 2

Reviewer 3 Report

Thank you for the hard work revising this paper. The reviewer understands the purpose of this study but still thinks that additional revisions are necessary. The authors still need to perform error analysis. At least Fig. 9 needs error bars. How did the authors determine the H2O2 concentration? Explanations of the method with error analysis are necessary.

Author Response

Once again, we would like to express our sincere gratitude for your valuable and insightful comments. Taking into consideration your feedback we have made the following revisions to the manuscript:

Comment 1:

Thank you for the hard work revising this paper. The reviewer understands the purpose of this study but still thinks that additional revisions are necessary. The authors still need to perform error analysis. At least Fig. 9 needs error bars. How did the authors determine the H2O2 concentration? Explanations of the method with error analysis are necessary.

Answer 1:

In subchapter 2.2, titled "Testing Method," we have provided additional information regarding the measurement technique for hydrogen peroxide concentration. We believe that this clarification will enhance the reproducibility of our study and assist readers in understanding the experimental procedures more effectively.

Furthermore, we have made enhancements to the "c* efficiency" graph by including error bars. Additionally, we have presented error values associated with the sensors used for measurement, which were utilized in the calculation of c*.

With kind regards,

The Authors

Round 3

Reviewer 3 Report

Thank you for revising the article. The authors appropriately corrected the issues the reviewer pointed out. The reviewer agrees to accept this paper.