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Article
Peer-Review Record

Investigation of Solid Deposit Inside L-Type Urea Injector and NOx Conversion in a Heavy-Duty Diesel Engine

Catalysts 2021, 11(5), 595; https://doi.org/10.3390/catal11050595
Reviewer 1: Anonymous
Reviewer 2: Anonymous
Catalysts 2021, 11(5), 595; https://doi.org/10.3390/catal11050595
Received: 16 April 2021 / Revised: 1 May 2021 / Accepted: 3 May 2021 / Published: 4 May 2021

Round 1

Reviewer 1 Report

  1. The modification of the title for more related to the contents of the manuscript should be considered as in ‘Investigation of solid deposit inside urea injector’ only sparse, limited information is presented related to the L-type injector.
  2. Inappropriate designation of figures. Figures 1 and 2 and 10 are missing. Figures 6 and 7  are double marked.
  3. Fig. 1 (designated as Fig.  6) presents L-type urea injector, whereas the photo in the top shows  I-typeone.
  4. Have the authors (for comparing) checked the interior of I-type injector (the solid deposit formation) as shown in fig. 7 (designated as Fig. 2)?
  5. The presented CFD simulations do not show the advantage of I-type injector in a convincing and unambiguous manner.
  6. Fig. 6 is not clear to be interpreted, the description which would allow the unambiguous interpretation of results should be elaborated.
  7. Results of experiments presented in Fig. 9 do not confirm the advantage of I-type than L-type injector and conclusions drawn in 163-169 lines are not confirmed in the results of studies.
  8. The conclusion that these studies are of fundamental importance for future research on lowering the emissions of NOx from  heavy duty diesel engines (lines 355-356) seems to be exaggerated.
  9. The text should be reviewed and corrected e.g. instead khristamto, H2O N2, there should be  Khristamto, H2O, N2 .

Author Response

Responses to reviews

 

The authors are very grateful with the comments and recommendations in order to improve the quality of this paper. We agreed and accepted the reviewer’s suggestion. The manuscript is revised carefully according to the reviewer’s comments and detailed corrections are listed below point by point. Responses to the reviewer’s comments are as follows:

 

Reviewer 1.

  1. The modification of the title for more related to the contents of the manuscript should be considered as in ‘Investigation of solid deposit inside urea injector’ only sparse, limited information is presented related to the L-type injector.

Answer:

The authors would like to thank for reviewer’s suggestion and comments to clearly the title for more related to the contents of the manuscript. The author agrees to change the title as shows:

 

“Investigation of solid deposit inside L-type urea injector and NOx conversion in a heavy-duty diesel engine”

 

 

  1. Inappropriate designation of figures. Figures 1 and 2 and 10 are missing. Figures 6 and 7 are double marked.

Answer:

The authors would like to thank for reviewer’s suggestion and comments to correct the double marked in the manuscript. The double marked already improved and check, as shows in line 88-89 (figure 1), 90-91 (figure 2) and 218-219 (figure 10).

Figure 1. The original urea injector from Hyundai D6CC diesel engine.

Figure 2. The solid deposit formation inside the original urea injector from Hyundai D6CC diesel engine.

Figure 10. The CFD model for SCR system (D6CC by Hyundai)[2].

  1. 1 (designated as Fig. 6) presents L-type urea injector, whereas the photo in the top shows I-type one.

Answer:

The authors would like to thank for reviewer’s suggestion and comments to correct figure 1. The improvement figure 1 as shows in line 88-89.

Figure 1. The original urea injector from Hyundai D6CC diesel engine.

  1. Have the authors (for comparing) checked the interior of I-type injector (the solid deposit formation) as shown in fig. 7 (designated as Fig. 2)?

Answer:

The authors would like to thank for reviewer’s suggestion and comments for asking to comparing solid deposits inside L-type and I-type injector. However, I-type injector does not hamper the gas flow like L-type injector. Based on the experiment and simulation, the quantity urea injection from I-type injector was constant and high. So, the author disagrees to check the I-type injector for this manuscript with Hyundai D6CC. However, we will consider to checking and comparing your suggestion for the future research with higher diesel engine.

  1. The presented CFD simulations do not show the advantage of I-type injector in a convincing and unambiguous manner.

Answer:

The authors would like to thank for reviewer’s suggestion and comments. The author disagrees that in the CFD simulation shows do not show the advantage of I-type injector. Even in the simulation shows a little improvement but can be effect to SCR system performance. The advantages from I-type injector not obtainable in the short term. As you can seen in the figure 1, that has solid deposit in L-type injector and in long term will be bad effect on the system. I-type injector has constant amount of urea and can produce high ammonia gas than L-type injector. And in the experiment also show that ammonia value and NOx conversion from I-type injector better than L-type injector and can validate the CFD simulation result.

  1. 6 is not clear to be interpreted, the description which would allow the unambiguous interpretation of results should be elaborated.

Answer:

The authors would like to thank for reviewer’s comment and suggestion in order to improve the quality of this paper. In the figure 6, we want to explain the 5-gas parameter such as H2O, N2, CO2, NH3 and O2 in the simulation to represent (NH2)2CO is used in the experimental system. Because the transform of chemical form cannot be displayed in the simulation with STAR-CCM+ but can be described by entering the chemistry properties that will be formed by the chemical process. The information will be showing at line 146-161:


Figure 6 shows the various gas in the SCR system based on time duration. These simulation study, used 5 gas parameter such as H2O, N2, CO2, NH3 and O2 to represent (NH2)2CO is used in the experimental system. The transform of chemical form cannot be displayed in the simulation with STAR-CCM+ but can be described by entering the chemistry properties that will be formed by the chemical process. This figure explains the various gas inside the system as used in the general reactions occurring for urea in the SCR system; reaction (1) is the thermolysis of urea; this process describes when NH3 reacts with NOx emission; reaction (2) is an isocyanic acid hydrolysis reaction to produce the NH3 by HNCO; and reactions (3) are standard SCR reactions to demonstrating NOx emission converted to N2 and H2O.

 

(NH2)2CO→HNCO+NH3                                                                                                                                 (1)

 

HNCO+H2O→NH3+CO2                                                                                                                                 (2)

               

4NO+4NH3+O2→4N2+6H2O                                                                                                                        (3)

 

 

  1. Results of experiments presented in Fig. 9 do not confirm the advantage of I-type than L-type injector and conclusions drawn in 163-169 lines are not confirmed in the results of studies.

Answer:

The authors would like to thank for reviewer’s suggestion and comments. The figure 9 shows that I-type injector produce higher NOx conversion efficiency than L-type injector. That explanation can be seen that in the blue line (I-type injector) higher value than the red line (L-type injector). Even the result inconstant but the average the I-type injector converted more NOx than original urea injector. As shows in line 169-175.

 

“Figure 9 compares the amounts of NOx conversion from the experiment. The suggestion urea injector converted more NOx than original urea injector. This result show that the suggestion urea injector has a suitable shape and position for urea injection in commercial SCR system by Hyundai D6CC; enhancing the urea particle conversion into ammonia and minimizing the possibility of solid deposits inside injector. Therefore, this urea injector is recommended to improve NOx conversion in Hyundai D6CC and can use for others commercial SCR system with different type of heavy-duty diesel engine.”

  1. The conclusion that these studies are of fundamental importance for future research on lowering the emissions of NOx from heavy duty diesel engines (lines 355-356) seems to be exaggerated.

Answer:

The authors would like to thank for reviewer’s suggestion and comments. Based on your suggestion we improve the conclusion line 355-356 as shows as:

 

Thus, this study has been a good reference for future research to decreasing NOx emissions from heavy duty diesel engines especially used similar parameter.”

  1. The text should be reviewed and corrected e.g. instead khristamto, H2O N2, there should be Khristamto, H2O, N2 .

Answer:

The authors would like to thank for reviewer’s suggestion, and we agree to checked and reviewed carefully to improve whole manuscript.

Author Response File: Author Response.pdf

Reviewer 2 Report

  Dear authors, the article is interesting and dedicated to the optimization
of a specific SCR system. The article is an extension of the previous
article focused on the assessment of the parameters of two type I and
L injectors with which the article has the same parts.
If possible, write what was the difference in the accuracy of the proposed
simulation with the results during the real test.

Author Response

The authors would like to thank for reviewer’s suggestion and comments. The CFD model we used in this simulation based on the real dimension of commercial system. Even the dimension and material we input was similar, still has many differences in the accuracy from simulation and experiment. But difficult to explain and find that differences. The difference in the accuracy of the proposed simulation with the real test as we know only spray model of injector. In the experiment with commercial SCR system, the urea injector will spray the urea liquid. That process will show the solid deposit phenomena in the wall of system. That phenomena will inform the transform quality from urea to ammonia in the system. however, in this simulation we only can show the quantity of ammonia gas value from saturation and vaporization result; and it can represent the transform quality from urea to ammonia without solid deposit phenomena in the system. This information was shows in line 110-116.

 

“In the experiment with commercial SCR system, the urea injector will spray the urea liquid. That process will show the solid deposit phenomena in the wall of system. That phenomena will inform the transform quality from urea to ammonia in the system. However, in the simulation that solid deposit difficult to showing. The value from saturation and vaporization result can represented the transform quality from urea to ammonia without solid deposit phenomena in the system.”

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The text should be carefully reviewed and corrected once again. There are some editioral and grammar mistakeses, e.g. "... and Each hole..." (line 78), "This result show... "  (line 170).

Please use the same convention for markings  in the text, e.g. Figure2 (line 83 or Fig. 5 (line 124), Time (s) in Figure 6 or Time, sec. inn Figure 9,  2. M. K. A. Wardana (it suggests one person) or as in 5. M. Khristamto, A. Wardana (it suggests two people) in References section.

Author Response

Responses to reviews

 

The authors are very grateful with the comments and recommendations in order to improve the quality of this paper. We agreed and accepted the reviewer’s suggestion. The manuscript is revised carefully according to the reviewer’s comments and detailed corrections are listed below point by point. Responses to the reviewer’s comments are as follows:

 

  1. The text should be carefully reviewed and corrected once again. There are some editioral and grammar mistakeses, e.g. "... and Each hole..." (line 78), "This result show... " (line 170).

Answer:

The authors would like to thank for reviewer’s comment and suggestion in order to improve the quality of this paper. The entire manuscript has been checked and revised carefully to improve the editorial and grammar mistakes.

 

  1. Please use the same convention for markings in the text, e.g. Figure2 (line 83 or Fig. 5 (line 124).

Answer:

The authors would like to thank for reviewer’s comment and suggestion in order to improve the quality of this paper. The entire manuscript has been checked and revised carefully to used same convection.

 

  1. Time (s) in Figure 6 or Time, sec. inn Figure 9,

Answer:

The authors would like to thank for reviewer’s comment and suggestion in order to improve the quality of this paper. The author already improves figures 6 and 9 based on reviewer suggestion and we already check to all figure to prevent a similar error.

 

Figure 6. Various gas in the system.

 

Figure 9. NOx conversion value by MEXA-7100 gas analyzer.

 

  1. M. K. A. Wardana (it suggests one person) or as in 5. M. Khristamto, A. Wardana (it suggests two people) in References section.

Answer:

The authors would like to thank for reviewer’s comment and suggestion in order to improve the quality of this paper. The author already improves naming on the reference section.

 

“2. M. K. A. Wardana, K. Oh, and O. Lim, “Investigation of urea uniformity with different types of urea injectors in an SCR system,” Catalysts, vol. 10, no. 11, pp. 1–14, 2020.

 

  1. M. K. A. Wardana, K. Oh, Y. J. Lee, Y. M. Woo, and O. Lim, “EFFECTS OF UREA INJECTION TIMING ON PREDICTING NO X CONVERSION IN SCR SYSTEMS,” Int. J. Automot. Technol, vol. 21, no. 1, pp. 137–145, 2020.

 

  1. M. K. A. Wardana, G. M. H. Shahariar, K. Oh, and O. Lim, “AMMONIA UNIFORMITY TO PREDICT NOX REDUCTION EFFICIENCY IN AN SCR SYSTEM,” Int. J. Automot. Technol., vol. 20, no. 2, pp. 313–325, 2019.”

Author Response File: Author Response.pdf

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