Effects of Abrupt Cross-Section Area Change on theMultiparameter Propagation Characteristics of Premixed Methane–Air Explosion in Pipes
Round 1
Reviewer 1 Report
The present work highlights a noble effort of the authors to experimentally understand the effect of abrupt changes in the cross-sectional diameter of gas pipes on the propagation of explosion characteristics including shock wave overpressure, attenuation coefficient, flame propagation and turbulence effect. The work comprehensively explores the various parameters associated with the transport and explosion of methane-air mixture inside a pipe. The results and analysis section clearly delineates the effect of changes in cross-sectional diameter of gas-carrying pipes on the explosion features. However, I have the following comments:
1. Line 31 – “Roadways or pipelines that have an abrupt change in their cross-section areas are widely are widely used in underground engineering tunnels or industrial pipelines.” How the word “ROADWAYS” is relevant in this statement? Further, “are widely” is written twice in the line. Kindly delete repeated words.
2. Line 112 – “The diameter of the middle part can be set to 0.2 m, 0.24 m, 0.28 m, 0.32 m, or 0.36 m…”. Change this line to “The diameter of the middle part is set to 0.2 m, 0.24 m, 0.28 m, 0.32 m, and 0.36 m for five different trials….”.
3. Figure 3, denoting the overpressure changes at different measuring points for V=0.18 m3, d=0.36 m, has 5 subplots exhaustively covering the ten measuring points. However, the upper and lower limits of the axes of these 5 plots are same. So, it is advised to plot the overpressure changes for the ten measuring points in a single plot (so that it becomes easier for the readers to visualize and compare the results).
4. As per the manuscript, Figure 3 presents the data for a middle pipe diameter of 0.36 m for a methane-air volume of 0.18 m3. However, similar plots for other values of middle diameter (0.2 m, 0.24 m, 0.28 m and 0.32 m) and premixed methane-air volume (0.23 m3 and 0.28 m3) cannot be found in this draft. Based on the comprehensiveness of the work, I would like to suggest the authors to include the results of the other possible combinations of d and V. And if it is not relevant, then kindly add one or two lines giving proper justification for the same.
5. Line 225 – Kindly write the name of the specific version of MATLAB used along with the mention of any specialised toolbox, if used.
6. Line 282 – Is there any specific reason of choosing SIMPLEC algorithm for pressure-velocity coupling (for the numerical experiments)?
7. Since the manuscript has dedicated a particular section on numerical modelling, the authors are requested to cite the following paper, based on finite volume method, in Section 3 at relevant location
a. Ashutosh Priyadarsan, Mohammad Saud Afzal; Numerical investigation of flow past a circular cylinder modified with a single groove at low Reynolds number. Physics of Fluids 1 February 2023; 35 (2): 027125. https://doi.org/10.1063/5.0137530.
English language use must be improved.
Author Response
Reviewer #1:
(1) Line 31 – “Roadways or pipelines that have an abrupt change in their cross-section areas are widely are widely used in underground engineering tunnels or industrial pipelines.” How the word “ROADWAYS” is relevant in this statement? Further, “are widely” is written twice in the line. Kindly delete repeated words.
[Response]:We greatly appreciate your valuable comments and suggestions. The word “ROADWAYS” is indeed not suitable for abrupt cross-section changes. Repeated word “are widely” has been deleted. For the revised content, please refer to the red font of the revised manuscript.
(2) Line 112 – “The diameter of the middle part can be set to 0.2 m, 0.24 m, 0.28 m, 0.32 m, or 0.36 m…”. Change this line to “The diameter of the middle part is set to 0.2 m, 0.24 m, 0.28 m, 0.32 m, and 0.36 m for five different trials….”.
[Response]:We greatly appreciate your valuable comments and suggestions. We have carefully revised 'Line 112' according to your suggestion, please refer to the red font of the revised manuscript.
(3) Figure 3, denoting the overpressure changes at different measuring points for V=0.18 m3, d=0.36 m, has 5 subplots exhaustively covering the ten measuring points. However, the upper and lower limits of the axes of these 5 plots are same. So, it is advised to plot the overpressure changes for the ten measuring points in a single plot (so that it becomes easier for the readers to visualize and compare the results).
[Response]:We greatly appreciate your valuable comments and suggestions. We have merged the 5 subgraphs into one graph according to your suggestion. For details, please see the revised manuscript.
(4) As per the manuscript, Figure 3 presents the data for a middle pipe diameter of 0.36 m for a methane-air volume of 0.18 m3. However, similar plots for other values of middle diameter (0.2 m, 0.24 m, 0.28 m and 0.32 m) and premixed methane-air volume (0.23 m3 and 0.28 m3) cannot be found in this draft. Based on the comprehensiveness of the work, I would like to suggest the authors to include the results of the other possible combinations of d and V. And if it is not relevant, then kindly add one or two lines giving proper justification for the same.
[Response]:We greatly appreciate your valuable comments and suggestions. The main purpose of this study is to analyze the variation law of gas explosion shock waves at abrupt cross-section areas. Only data with a middle pipeline diameter of 0.36m was taken when the volume of methane air was 0.18m3. If three different volumes and five different middle pipeline diameters are taken into account, 15 plots will appear. Therefore, this report only includes one figure to illustrate the variation law of gas explosion shock waves at abrupt cross-section areas.
(5) Line 225 – Kindly write the name of the specific version of MATLAB used along with the mention of any specialised toolbox, if used.
[Response]:We greatly appreciate your valuable comments and suggestions. Based on your suggestion, the name of the MATLAB version used has been added and the specific toolbox used has been explained. For details, please see the revised manuscript.
(6) Line 282 – Is there any specific reason of choosing SIMPLEC algorithm for pressure-velocity coupling (for the numerical experiments)?
[Response]:We greatly appreciate your valuable comments and suggestions. The solution approach of the SIMPLEC algorithm is the same as SIMPLE, with the only difference being the introduction of a correction function for surface flux, which is mainly used to solve the problem of difficulty in obtaining solutions for pressure velocity coupling methods and improve the convergence speed.
(7) Since the manuscript has dedicated a particular section on numerical modelling, the authors are requested to cite the following paper, based on finite volume method, in Section 3 at relevant location
[Response]:We greatly appreciate your valuable comments and suggestions. According to the author's suggestion, multiple new references have been added regarding the use of finite volume method in numerical simulation research. For details, please see the revised manuscript.
Author Response File: 
Author Response.docx
Reviewer 2 Report
(1) line 32, remove one "are widely"
(2) The paper can be improved, if the shock wave photos in the pipe line are presented.
(3) the shock wave structures in Fig. 6 should be included.
(4) how to make sure, the combustion is completed in the combustion chamber? The mechanism should be mentioned.
Author Response
Reviewer #2:
(1) line 32, remove one "are widely".
[Response]:We greatly appreciate your valuable comments and suggestions. Repeated word “are widely” has been deleted. For the revised content, please refer to the red font of the revised manuscript.
- The paper can be improved, if the shock wave photos in the pipe line are presented.
[Response]: We greatly appreciate your valuable comments and suggestions. Due to the opaque steel pipe used in the experimental pipeline system, it is difficult to capture shock wave photos in the experiment. In the later research, transparent high-pressure pipelines will be added to complete this aspect of research.
(3) the shock wave structures in Fig. 6 should be included.
[Response]: We greatly appreciate your valuable comments and suggestions. In the viscous model, due to the selection of the standard k-e model, the shock wave structure of the standard k-e model does not appear particularly obvious. However, the shock wave structure is already included in the figure.
(4) how to make sure, the combustion is completed in the combustion chamber? The mechanism should be mentioned.
[Response]: We greatly appreciate your valuable comments and suggestions. By installing a pressure sensor and a temperature sensor in the combustion chamber, if the pressure and temperature undergo an increase, a decrease, and then stabilize to a normal pressure, it indicates that the explosion has been completed. This section is added in section 2.2. For details, please see the revised manuscript.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
I recommend acceptance since the authors have satisfactorily answered all my queries.
This is fine.
