A Mathematical Model of Industrial Waste-Derived Fuel Droplet Combustion in High-Temperature Air

Round 1

Reviewer 1 Report

This paper presents a mathematical model developed to predict the ignition and combustion characteristics of a single composite liquid fuel. The model takes into account the sequence of the main chemical transformations and thermophysical interactions between the droplet and surrounding air environment. The proposed model appears to be promising, however, the validation of the model should start by comparing the ignition delay time of a pure substance droplet to check the functional basis of the model and eliminate the effects of impurities in the validation steps. There are plenty of literature data available to compare. On another note, it is suggested to perform mesh convergence analysis, and specify and present the convergence criteria of the simulations to check the accuracy of the numerical results. The manuscript also requires further proofreading (one example is below). In summary this paper requires a major overhaul to be accepted for publication in Applied Science. 

1.       Ln 86: The sentence is not complete “.. CLF droplet of a ?? in an air medium heated..”

Author Response

Please find a detailed response to Reviewer 1 in attached file.

Author Response File: Author Response.doc

Reviewer 2 Report

The manuscript presents the numerical study on the evaporation, flow, and combustion of industrial waste-derived fuel droplets within static and flowing air ambient. The research is a valuable attempt to solve a complex CFD problem to help understand the evaporation and reaction process of different compositions under different conditions. The model description part of the research is well-written and clear. However, the discussion part needs to be improved to make the manuscript more readable to the general audience. Detailed comments are as follows:

In line 308, ‘distanse’ should be distance.

Ranz and Marshall correlation is used to evaluate both the mass transfer and heat transfer coefficient, which is selected by ANSYS FLUENT by default. Can you justify if this model is really suitable for the physical model?

In the discussion part, only ignition delay time is presented with different conditions. I understand that it would be convenient to compare the time with the experimental observation. But is this time really important for the application purpose?

In Figure 9, there is a big difference between the experimental and simulation result at intermediate temperatures, which make me suspect there is some temperature-related feature missing in the numerical model. At least, I wouldn’t call this a ‘satisfactory agreement‘.

A qualitative figure of numerical result, i.e. in comparison with Figure 2, would be really helpful and interesting.

As the authors said in lines 481 and 482, the CLF droplet temperature, fuel component composition changing during heating, unsteady release of volatiles, etc, should be able to be extracted from the simulation easily. I believe it will make the paper more informative if the authors could include some figures and discussions of these important parameters.

Author Response

Please find a detailed response to Reviewer 2 in attached file.

Author Response File: Author Response.doc

Round 2

Reviewer 1 Report

Recommended for publication.

Author Response

Please find attached file with detailed response to Reviewer 1.

Author Response File: Author Response.doc

Reviewer 2 Report

The topic and method of the manuscript are interesting. But unfortunately I think the depth and breadth of the discussion part are  still not good enough for publication after the first revision. The authors only provide the result of ignition delay time in the discussion part, which differs from the experimental result and might make the audience doubt if the model really works for such a complicated problem.

I would like to encourage the authors to further improve the model and resubmit the manuscript when they feel confidant enough to provide more informative results.

Author Response

Please find attached file with detailed response to Reviewer 2.

Author Response File: Author Response.doc

Round 3

Reviewer 2 Report

Manuscript can be published after the revision.