Impact of Swirling Flow on the Overall Cooling Effectiveness and TBCs Insulation Characteristics of Turbine Vane
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors
The authors studied the influences of swirl on the cooling performances of the turbine with or without TBCs. This paper can be published in the journal after major revisions:
1) It is not acceptable that the coarse, fine and medium grids lead to the same results!
2) Boundary condition must be presented for inlet, outlet, wall considering hydrodynamic and thermal aspects.
3) All parameters must be defined clearly, for instance, swirl number.
4) Governing equations must be presented. How did you introduce boundary condition when the equations have not been considered?
5) You need to introduce the software and numerical method comprehensively.
Comments on the Quality of English Language
Minor editing of English language required
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for Authors
Manuscript Number: coatings-2601612-v1
Full Title: Impact of swirling flow on the film cooling and TBCs insulation characteristics of a turbine vane
I – General Comments
The present manuscript numerically investigates the cooling performance of the first stage of a thermal turbine with/without coatings because of influence of lean premixed combustion to guide the integrated design of the first-stage turbine vane. In general, the obtained results are interesting for the readers. However, there are recommendations/questions addressed to the authors, before to accept their manuscript as Coatings´ paper.
II - Specific Comments
(i) In “Abstract”, the main contribution of the present work must be introduced and clarified; and the present state of the art concerning the investigated topic must be introduced and contextualized too.
(ii) In “Introduction”, the authors did not cite previous works early published in Coatings. Why? Are there other publications given by other authors about the research topic in Coatings? That key point needs to be clarified by authors to justify the intended publication. It is recommended an introduction, including justification, of the adopted methodology too.
(iii) In “Section 2”, the authors must clarify the assumed hypotheses for the mathematical formulation including the corresponding justifications. The manuscript is poor in terms of mathematical formulation, since governing equation and boundary conditions have not been included into the technical discussions.
(iv) Figure 1, that already illustrates the investigated problem, is welcome aiming to support the comments from topic (iii) above presented. Figure 1 and Table 1 were not introduced into the “Section 2”.
(v) Please, make sure as the local energy is dissipated for any point of the flow field because of turbulence.
(vi) Still in “Section 2”, if the authors utilize a numerical method, it is important to include some explanation about implementation of the present method algorithm.
(vii) Equation 5 was omitted into the manuscript.
(viii) The concepts of compressible flow and Mach number (at high speed) must be introduced and contextualized by authors.
(ix) What is the measurement uncertainty of the (experimental) data used as support? See, for instance, in Figure 3.
(x) Figures 8 and 9 need more discussions with sense of physics.
(xi) Figure 13 must be better discussed aiming to explore the captured effect by numerical methodology.
(xii) In “Conclusions”, it is necessary to include comments with respect the numerical results behavior as compared as previous works (specially, experimental data, when available). In closing, it is important to complete the manuscript with perspectives for a future research. Finally, the main contribution of the present manuscript should be clarified aiming to justify its publication in Coatings.
III - Recommendation for the Coatings´ editor
In my opinion, the present manuscript needs attend all topics above presented. Upon consideration of all points above, I think the paper could be considered for publication in Coatings.
Comments on the Quality of English Language
Minor editing of English language required.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for Authors
It is necessary to explain which program (commercial, openFoam, some other was used for simulation.
Important formulas are missing, the equations are not cited in the text at all.
Chemical equations should preferably use integer coefficients.
These are important insufficiences and it is impossible for the reviewer to evaluate the manuscript without the missing information.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for Authors
Accept in present form
Comments on the Quality of English Language
Minor editing of English language required
Author Response
Thank you.
Reviewer 2 Report
Comments and Suggestions for Authors
Manuscript Number: coatings-2601612-v2
Full Title: Impact of swirling flow on the film cooling and TBCs insulation characteristics of a turbine vane
The original text of the manuscript has been satisfactory revised. In my opinion, the manuscript can be published as Coatings´ paper.
Comments on the Quality of English Language
Minor editing of English language required.
Author Response
Thank you.
Reviewer 3 Report
Comments and Suggestions for Authors
Brief summary:
The paper aims to describe the combined effect of lean premixed combustion on the heat load and the cooling performance of the turbine stage. Based on CFD modelling the researchers focus on analysing namely the effect of swirl. The results of three different swirl numbers 1.0, 1.3, and 1.6 are presented, however, it is not obvious which of them appears to be the best or the reason for their choice (except for the value 1.3 which seems to be the same as in experimental values used for comparison).
Broad comments:
Although the authors added the missing information and improved the original paper significantly, there are still some formal items that should be corrected.
1. Three papers with almost the same authors published recently in Coatings were added to the introduction. However, the numbering of the citations remained unchanged. It is necessary to renumber the references.
2. The word “Although” at the beginning of the last paragraph in the Introduction should be omitted, as there is no contradictive information in the following text, therefore it makes no sense to use this conjunction. (line 101)
3. The authors tried to deal with my comment concerning the application of integer numbers in chemical reactions notation, but their correction is unacceptable, their present notation of the chemical reactions is much worse than the original one. Moreover, they cite reference [31] and still write all the reactions in a completely different way. The letters cannot be in italics, the first two reactions are unidirectional, it is necessary to correct the arrows in them. If the authors insist on the new version of the chemical equation, they should explain the meaning of the box brackets and the numbers in superscripts.
4. The equations (5)-(8) should correspond with the description of the physical characteristics on lines 144-146. It is necessary to correct the description: the vectors (heat flux, velocity, and gravity) must be written in bold italics and the kinetic energy per unit mass should be written in lowercase. (“where k is the kinetic energy per unit mass, e is the internal energy per unit mass, r is the specific heat source, q is the heat flux vector, u is the velocity vector, g is the gravity vector, ρ is the density, τ is the shear force, and t is time”). The velocity vector in the equations should then be written in the same way as in the description (bold lowercase), and the second term in the momentum conservation should be corrected to EQ1, because it is not the same as EQ2 (see the attached file peer-review-32780241.v1.pdf).
5. The letter S (the same as the swirl number) was probably used for axial position in Figures 3 and 5. It is confusing and it must be corrected.
6. The conclusion part is unnecessarily complicated, it is hard to understand the main benefits and findings of the paper. Namely, the first point presents temperatures at the axial position 1.21d without explaining that the temperatures in larger axial positions differ less for different swirl numbers. The summary of the conclusion seems to be fine, but the information which swirl strength and swirl angle is "appropriate" is missing.
7. Last but not least, it follows from the revised introduction that the authors are presenting the fourth paper dealing with a similar, or perhaps the same, topic. A thorough comparison of these papers shows that they used different turbulence models in these papers ([28] k-kl-ω, [29] transition k-kl-ω, [30] realizable k-ε, manuscript SST k-ω). The readers should be surely interested what were the reasons for the application of different models, and what are the advantages and disadvantages of them.
Specific comments:
l.53 “CO2” must be corrected to “CO2“
l.89 The name of the author (Sohn) must be written in lowercase.
l.169-171 The same reference is cited twice within three lines, it might sound better, if the authors of the cited reference were named in the first citation and then the two sentences are merged into one: “as observed in the experimental results reported by Stopper et al. [23]. The peak temperature is close to the experimental results, while the magnitude of the high-temperature region is slightly wider.”
l.227-8 “A positive swirl angle can be observed near the hub, while a negative swirl angle e near the pitch.” The meaning of the single letter “e” is unclear, it is necessary to revise the sentence.
Comments for author File: Comments.pdf
Comments on the Quality of English Language
The word “Although” at the beginning of the last paragraph in the Introduction (line 101) should be omitted, as there is no contradictive information in the following text, therefore it makes no sense to use this conjunction.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
