Ultra-Lean Premixed Turbulent Combustion: Challenges of RANS Modelling

Round 1

Reviewer 1 Report

This article aims to omparison between computed results and experimental data on trends of mean flow velocity, turbulence, temperature and mixture stratification . The experiments were focused on the comparation of two different consolidated approaches: the Coherent Flame Model (CFM) and the Flame Area Model (FAM).

The introduction clearly sets out the problem under investigation. The methodology is adequate. Model formulation is good presented. Model Setup and Validation are described. I also appreciate the addition of the Mesh sensitivity analysis chapter at the end of the post. The topic of the contribution is really very current, while the methodology and processing of the research is at a very good level.
Several minor issues need to be solved before further consideration.

 

It would be appropriate to graphically represent the parameters from Figure 5 (y and r), e.g. in Figures 3 or 4. It is not entirely clear what the distances are.

Figure 10 - is the Exp label correct? It should be an empty circle, but it doesn't look like that.

Author Response

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Reviewer 2 Report

This study respresents the experimental and numerical analysis of lean methane-air combustion in specific burner. The topic is interesting for publication in this journal. The following comments should be adressed: 

1. Loomping refereces should be avoided. Instead, summarize main contribution of each reference into separate sentence.

2. What is the reason to select CFM and FAM models to implement into open source CFD code?

3. Which air excess ratio is achieved in the reaction zone? Paper title indicates to ultra lean conditions. What are these conditions? Air excess ratios (lamba above 2.0) in SI engines with different fuels are already extensively studied experimentally and numerically. Please comment it.

4. It is unclear how this study and conclusions can be correlated to SI engine combustion? This study does not include ignition process (flame kernel development) that becomes important when lean mixtures are applied and responsible for cyclic combustion variability. Moreover, combustion in IC engines is always under transient flow conditions (change of flow data over the time) while it is not the case in this study. This should be clarified and emphasized ih this study.

Author Response

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Reviewer 3 Report

Dear Editor/Researcher,

                 The manuscript titled 'Ultra-lean premixed turbulent combustion: challenges of RANS modelling' aimed to improve thermal efficiency and emission reductions. The article is very well written. However please find the following comments to be addressed before its publication.

* The abstract is very clear and drafted well

* Introduction should be included with statement of the problem as well as novelty of the the work.

*Try to avoid lumped references in the modelling section. 

*Schematic diagram of the work is missing in the manuscript. 

* What is the specific reason for choosing standard k − ϵ model for turbulence method?

*Results and discussions figures quality can be improved. 

* Conclusion is nicely written with future recommendation. 

 

 

Author Response

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