Supersonic Shrouding Methane Mixtures for Supersonic Combustion Coherent Jets

Round 1

Reviewer 1 Report

R E V I E W

“Supersonic Shrouding Methane Mixtures for Supersonic Combustion Coherent Jets”

for METALS  ID 1960709

Line 75 -76 – How did nitrogen appear in the discussion? At the current stage, up to this point, there was talk of other gases. Explain the reason/motivation for using nitrogen in the context described by the current state. In fig. 2 there are other fuels that you don't mention anything about at the current stage (Kerosene).

Fig. 2 – Explain the role of the additional oxygen and kerosene burner. Does it work all the time? Is it used to ignite the main jet? How much of the total thermal input goes to this burner?

Line 111 – Define static pressure by two symbols: Ps (from relation 1) and P. What can be understood from this? What are two different static pressures? In addition, in the presented equations, you use the small letter "p" for the same static pressure? We recommend you use unit notations.

Line. 145 – Not only nitrogen but also methane. Why was methane omitted from the explanations?

Line 127 – What kind of calculation is applied? Until chapter 3. "Results and Discussion" mentions nothing about the calculation method applied to the constructed model. Why?

Fig. 6 – The curve is drawn incorrectly. You cannot work with different percentages of nitrogen at the same time (this is what the diagram says). I think that for each nitrogen content there is a curve of the variation of the speed of the center of the jet. Reflect on the mistake or explain better the physical meaning of the curve in figure 6. How do you experimentally prove the curve in figure 6? The Pitot-Prandtl tube mentioned as a measuring device changes its dimensions in compositionally inhomogeneous jets. It seems that this does not bother you.

Line 226 – You must give a physical explanation for this decrease in the length of the jet (not just a finding) in correlation with the increasing nitrogen content. A finding in a research article is not enough.

Line. 240 – 249 – The experimental finding regarding the decrease in density is not supported by numerical data resulting from modeling, nor by a phenomenological explanation. Only the combustion temperature of methane is not sufficient as a justification. The process is much more complex and is related to mixing oxygen with the resulting combustion gases. We recommend you be much more specific in the explanations given. When you mention changes to the jet, you must immediately mention the influence this has on the final purpose of this jet - that of transferring heat to the electric arc furnace slag. But, after the introduction, this correlation with the final goal is totally neglected, everything is reduced to findings regarding the jet and that's it.

Fig. 8 – Where can you read y = De from the diagram? In addition, the resulting gas will have the same density after establishing the mixing proportions between the gases (9:1, 8:2, etc.). How do you explain the variation of the curves if you put "surrounding gas density" on the ordinate, which is constant from the point of view of the compounds and variable only because of the temperature (a parameter that does not appear on the diagram)? How do experimentally confirm the curves in fig. 8 for them to be credible?

Line 265 – The extra letter "e" probably comes from Te.

Line 277 – "...the temperature core length reaches 32 De..." Which length, which core? How do you correlate a temperature with a length? Extremely unclear!

Line 283 – You must support your statements with experimental data. From the drawing of the experimental model, it is not clear how you measure the temperatures of the jet longitudinally and radially. At high temperatures in the jet, the thermocouple method (as shown in the drawing) does not stand up.

Fig. 9 – How was the diagram drawn?

Fig. 10 – How were the presented figures obtained? What calculation model did you use? The external methane flame must influence the radial temperature of the jet inside and outside. The figures are not physically and phenomenologically credible because, naturally, as the distance from the inlet nozzle increases, the mass of the jet must increase as a result of mixing with the other gases, which is not the case from the diagrams.

Fig. 11 – If you correlate the turbulence in fig. 11 with the temperature distribution in fig. 10 you will get another temperature distribution in figure 10. What is your opinion?

Conclusions – There is talk of "...simulation and experimental methods..." but the paper does not present the method of measuring the lengthwise speed (but only in one place), the lengthwise and radial temperatures, the lengthwise and radial density, also presenting the numerical data of the measurements. The whole work is based on some results of modeling for which nothing concrete is said, such as the choice of the grid, the boundary conditions, the software used, etc.

Recommendation:

The work must be fundamentally revised and massively supported with experimental data. Without this approach, I will have to recommend its rejection.

 

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Paper review metals-1960709 is titled "Supersonic Shrouding Methane Mixtures for Supersonic Combustion Coherent Jets".

 

This interesting issue, which the authors of this paper deal with, is crucial in the steelmaking process in electric arc furnaces. In order to study the supersonic coherent combustion stream under various methane-nitrogen mixing conditions, these authors used a CFD approach. 

 

Good points of this paper:

These studies are supported by experiment. A review of the literature is sufficient, in my opinion. A total of 29 sources were used. These are mostly good scientific journals. The drawings are of good quality.

 

Paper improvement suggestions:

I suggest correcting this sentence in the abstract: "Based on the six-component combustion mechanism of methane and the Eddy Dissipation Concept combustion reaction model, computational fluid dynamics software was used to simulate the supersonic combustion coherent jet under various methane–nitrogen mixing conditions." From this sentence it follows, I may be wrong, that the CFD approach to the simulation was used on the basis of the methane combustion mechanism. Of course, I understand everything that is written here, but it doesn't make sense to me.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

I will give my consent for publication only when the authors will insert in the text of the work (using a different color) all the explanations that they have offered me to my observations. Until now, this has been done partially and to a very small extent.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf