Modeling of the Effect of Carrier Gas Injection on the Laminarity of the Plasma Jet Generated by a Cascaded Spray Gun

Round 1

Reviewer 1 Report

Please see the attachment.

Comments for author File: Comments.docx

Author Response

 

Thank you for the comment. Sorry for there is no available result on the influence of the powder grain size distribution and powder feed rate right now. We are dealing with this kind of simulation. However, we added some relationships between this simulation and the coatings from previous work. I hope this can help to understand our work and meet your expectations.

 

1.30 I was not sure whether cold spray is suitable to listed among these spraying methods with high temperature. Therefore, I deleted the detonation spraying.

These processes include plasma spraying, flame spraying, high-velocity oxygen fuel spraying and others.

1.32 & 1.32 I am sorry for the confusing expression. I have revised it.

This feature makes plasma jets able to melt all materials, which leads to a huge selection of materials.

 

Reviewer 2 Report

The authors carried out the studies on “Modeling of the effect of carrier gas injection on the laminarity of the plasma jet generated by a cascaded spray gun” The authors carried out the systematic analysis on the plasma spray torch. However, the authors need to be clarified the following queries in the manuscript. 

1.     Why the authors performed this study.

2.     As mentioned in the authors, the design is taken from the reported literature to carry out the simulation, since it is meaning that the gun is existing in the market. What authors are suggesting to improving the existing gun from this study. 

Author Response

Thank you for the kindly comments, here are the respond to the comments:

 

1. The study is performed because the authors noticed the potential of plasma jet in laminar flow state in thermal spray technology. Till now, some studies have shown laminar plasma sprayed coatings has different structures and this technology has higher controllability and reproducibility. However, the laminar plasma jet is easy to be affected by the carrier gas. So, the cascaded plasma torch with high potential to generate a laminar plasma jet is studied to find out whether we can obtain a quasi-laminar plasma jet with higher stiffness so that the carrier gas cannot disturb the laminar flow state. This reason is added in the latest manuscript.
2. In fact, the authors are not suggesting improving the plasma torch, but to find the characteristics of the plasma jet generated by the plasma torch and how to characterize it. In this study, we focused on the laminarity of the plasma jet. Because we found the laminar flow state of the plasma jet can affect the spraying process and the coating structure. And we also found the cascade SinplexPro^TM torch has a potential to generate laminar or quasi-laminar plasma jet. So, we studied the arcing process and the plasma jet to find out whether there is a chance to produce a laminar plasma jet with higher stiffness by this cascaded plasma torch to solve the problem of powder feeding.

All the contents about the responds have been also added in the latest manuscript to clarify the necessity of the work. And I hope this can meet your expectations.

Reviewer 3 Report

The article presents the results of simulation studies of the arcing process inside the cascaded SinplexPro ™ plasma spray gun and the flow characteristics of the generated plasma. The modeling outlined may be of utilitarian importance to SinplexPro ™ spray gun practitioners, but I have the following comments for the article:

 

The article presents modeling of the operation of a selected gun for thermal spraying, but there was no discussion consisting in comparing it to the existing solutions. The modeling performed is either not supported, or is supported to a very small extent by experimental research.

 

Thermal spray guns are designed to produce a variety of coatings, but the article itself does not apply to coatings. The research presented in the article focuses on the modeling of the gun's work itself and does not correlate with the impact it has on the formation of the coating, its structure, properties, etc. Therefore, the content of the article itself raises my doubts as to whether it should be published in the Coatings journal.

 

I believe that the article should be supplemented either with a discussion comparing the obtained results with existing similar solutions, or with research showing what influence the obtained research results have on the structure and properties of coatings.

 

Author Response

 

Thank you for the kind comments!

Here we discovered the possibility of this spray gun capable of generating the laminar plasma jet, and then investigated it holistically from the inside out. Since most studies focused on either internal arcing process or external plasma jets, and these two parts were not combined well. Because this kind of overall research is currently insufficient that we are conducting this research.

Our main purpose of this work is to study the laminarity influence on the coatings. So far, previous studies have shown that the flow state of the plasma jet has an influence on the coating structure. As mentioned in the manuscript, the temperature and velocity gradients of the laminar plasma jet are lower, and the particles will be at a consistent temperature and velocity over a wider spray distance, which is beneficial to improve the controllability of the process. At the same time, it has also been proved that laminar plasma spray can obtain coatings with different structures at different distances. However, the commercial laminar plasma torch is not designed for spraying. And the laminar flow state is fragile, easily to be affected. This study focuses on the laminarity of the plasma jets generated by plasma torch with similar cascaded structure. It may generate a quasi-laminar plasma jet with high stiffness that can be used instead of laminar plasma jets. This study is to provide a foundation for the subsequent coating work. So, the plasma, as the most basic tool for coating preparation, I think the study of it is closely related to coating.

Although there are few studies that are completely consistent to this study. The effect of laminar flow characteristics on coating structure has been added to the introduction and discussion part of the paper. I hope it can meet your expectations.

Round 2

Reviewer 3 Report

The article supplemented in a few sentences the information on how the plasma flow affects the quality of the coating.

However, this does not change my last assessment of the article. I still believe that the research presented in the article focuses on modeling the work of the gun itself and does not correlate it with the impact it has on the production of the coating, its structure, properties, etc. The article also does not contain a discussion comparing the obtained results with other solutions, as well as what influence have the obtained test results have on the constitution of coatings.