Effect of Pre-Combustion Chamber Nozzle Parameters on the Performance of a Marine 2-Stroke Dual Fuel Engine

Round 1

Reviewer 1 Report

The manuscript deals with a numerical analysis of pre-chamber on the marine two-stroke dual-fuel engine. The research methodology is well presented, they have reported a clear flow chart. The analysis couple both 1-D and 3-D simulations. Looking at the results, the model predicts with good accuracy the NOx emissions and in-cylinder pressure traces. The paper is well presented, however, some minor remarks have been highlighted from the reviewer. The authors should revise the paper with more physical details.  Overall is a good paper, I would like to recommend this paper with minor revision.

Some minor remarks:

The authors should add space between the number and units of measurement, could you please revise all paper and tables?

 

Which is the Natural Gas composition used during the simulations? Could the authors report the fuel composition?

 

Has figure 5 already published? If yes, could the authors link the reference?

 

Figure 11 and 17, could the authors focus from -30 to 60 deg bTDC to improve the readability of this chart? Then you can report the RoHR in kJ/°CA to minimize the number of digits.

 

Section 3.2.2, the authors report: "It can be seen that the peak in-cylinder pressure gradually decreases as the diameter of the nozzle increases", why? Could the authors report more detailed analysis?

 

Figure 13 (B), remove the x-label "crank angle" you should add nozzle diameter, then looking the HC emissions is almost flat you can revise the y-axis starting from 3 up to 7 g/kWh.

Author Response

Thank you very much for your comments. The manuscript is entitled as follows: “Effect of Pre-Combustion Chamber Nozzle Parameters on the Performance of a Marine 2-stroke Dual Fuel Engine” (Manuscript ID: processes-646970). We also wish to take this opportunity to thank the reviewers for their constructive comments and valuable recommendations. We have carefully revised the manuscript according to reviewers’ suggestion.

Our responses to the comments are listed below:

Point 1: The authors should add space between the number and units of measurement, could you please revise all paper and tables?

Response 1: We have revised our manuscript of all paper and tables.

Point 2: Which is the Natural Gas composition used during the simulations? Could the authors report the fuel composition?

Response 2: Yes, we added the Natural Gas composition used during the simulations. The main modifications are as follows:

In addition, the Natural Gas composition used during the CFD simulations mainly included 95.1% methane, 2.53% ethane, and other gases. The natural gas fuel lower calorific value was 47.64 MJ/kg.

Point 3: Has figure 5 already published? If yes, could the authors link the reference?

Response 3: Yes, figure 5 has been already published on the CIMAC paper. As requested by the second reviewer, I have changed figure 5 because it's not clear enough and doesn't have numbers on the Y-axis. Besides, the citation for the new figure has been added.

Figure 5. Lean-burn DF engine Otto combustion limits

 

Point 4: Figure 11 and 17, could the authors focus from -30 to 60 deg bTDC to improve the readability of this chart? Then you can report the RoHR in kJ/°CA to minimize the number of digits.

Response 4: Figure 11 and 17 has been modified as follows:

Figure 11                                                                               Figure 17

Point 5: Section 3.2.2, the authors report: "It can be seen that the peak in-cylinder pressure gradually decreases as the diameter of the nozzle increases", why? Could the authors report more detailed analysis?

Response 5: We have reported more detailed analysis. The main modifications are as follows:

This is because when the diameter of the nozzle is too large, the jet flame velocity from the pre-combustion chamber decreases, which means that the flame needs more time to distribute inside the combustion chamber - making the combustion duration longer. Therefore, peak pressure decreases with the increase of the PCC nozzle diameter.

Point 6: Figure 13 (B), remove the x-label "crank angle" you should add nozzle diameter, then looking the HC emissions is almost flat you can revise the y-axis starting from 3 up to 7 g/kWh.

Response 6: Yes, we have revised Figure 13 (B). The main modifications are as follows:

Figure 13 (B). HC emissions under different PCC nozzle diameters

Thank you very much for the excellent and professional revision of our manuscript.

Yours sincerely,

Hao Guo

Author Response File: Author Response.pdf

Reviewer 2 Report

Dear Authors,

 

Your paper is in good shape. Hence, I would suggest it for publication after resolving the below issues.

 

L44-45: revise sentence

L90: affects

Section 2: Please, make it clear that the engine data is your measurement or you are using other's work. Either of the above, measurement uncertainty has to be discussed.

L141-142: Please, show the calibration procedure.

Please, detail all abbreviations at their first occurrence.

Figure 5: Either add numbers to the axes in this figure or move it to the introduction since it is not a result in this form. If it is not your product, add a citation to it.

Figure 6: Consider using a single vertical axis since the pressure ranges are rather similar.

L239: In Fig. 9

L244-5: Show the results to support your statement.

Figure 10: D = 24 mm

Figure 11: Consider using kJ or MJ/°CA.

What is the currently used PCC nozzle diameter and angle?

Author Response

Dear Reviewer,

Thank you very much for your comments. The manuscript is entitled as follows: “Effect of Pre-Combustion Chamber Nozzle Parameters on the Performance of a Marine 2-stroke Dual Fuel Engine” (Manuscript ID: processes-646970). We also wish to take this opportunity to thank the reviewers for their constructive comments and valuable recommendations. We have carefully revised the manuscript according to reviewers’ suggestion.

Our responses to the comments are listed below:

Point 1: L44-45: revise sentence. L90: affects. L239: In Fig. 9

Response 1: I have changed L44-45 sentence, L90 affects, and L239: In Fig. 9.

The main modifications at L44-45 are as follows:

The main advantages of this engine include high efficiency at high load, high mean effective pressure, and low NOx emissions.

Point 2: Section 2: Please, make it clear that the engine data is your measurement or you are using other's work. Either of the above, measurement uncertainty has to be discussed.

Response 2: The engine data was obtained from the marine installation manual of the WinGD 5RT-Flex50DF engine.

Besides, all other reference conditions refer to the ISO standard (ISO 3046-1). The following tolerances for BSPC and BSGC are taken into account: +5% for 100-85% engine power.

Table 1. 5RT-Flex50DF engine dimensions

Parameter	Value
Bore	500 mm
Stroke	2050 mm
Cylinder Number	5-8
Speed	124 r/min
Power	8640 kW
Compression Ratio	12
Brake Specific Pilot Fuel Consumption (BSPC) (DF Mode)*	1.8 g/kWh
Brake Specific Gas Consumption (BSGC) (DF Mode)*	142.7 g/kWh
*All other reference conditions refer to ISO standard (ISO 3046-1). The following tolerances for BSPC and BSGC are taken into account: +5% for 100-85% engine power.

Point 3: L141-142: Please, show the calibration procedure. Please, detail all abbreviations at their first occurrence.

Response 3: Yes, we have changed L141-142 sentence and detailed all abbreviations at their first occurrence. The main modifications are as follows:

L141-142: This GT model uses the user defined combustion heat release rate to simulate the DF engine combustion. The heat release rate was determined from the experimental data under 75% engine load, which can accurately predict the performance of the LP-DF engine.

Point 4: Figure 5: Either add numbers to the axes in this figure or move it to the introduction since it is not a result in this form. If it is not your product, add a citation to it.

Figure 6: Consider using a single vertical axis since the pressure ranges are rather similar.

Response 4: I have changed figure 5 because it's not clear enough and doesn't have numbers on the Y-axis. Besides, the citation for the new figure has been added. Figure 6 has been fixed.

Figure 5. Lean-burn DF engine Otto combustion limits                           

 Point 5: L244-5: Show the results to support your statement.

Response 5: The results of my statement are from Figure 9.

 

Items	-3°CA
D = 10 mm	The flame front has not yet reached the chamber bottom
D = 16 mm	The flame front has reached the chamber bottom
D = 24 mm	The flame front has not yet reached the chamber bottom

Figure 9. Temperature distribution in the combustion chamber

 Point 6: Figure 10: D = 24 mm. Figure 11: Consider using kJ or MJ/°CA.

Response 6: Figure 11 has been modified considering the use of kJ/°CA.

Figure 11

Point7: What is the currently used PCC nozzle diameter and angle?

Response 7: At present, the PCC nozzle diameter that used in the LP-DF engines is D = 16 mm with an angle of 65°.

L123-4 The PCC nozzle diameter of this engine is normally 16 mm with an angle of 65°.

Thank you very much for the excellent and professional revision of our manuscript.

Yours sincerely,

Hao Guo

 

Author Response File: Author Response.pdf