The Influence of Voltage on Gliding Arc Discharge Characteristics, the Composition of Air Plasma, and the Properties of BG-11 Medium

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Gliding Arc Discharges are devices for producing low-temperature plasmas for medical, food processing and agricultural applications. 

The present work presents a detailed characterization of one such device, including: plasma production, evolution of the discharge in time as a function of applied voltage, determination of the mixture of chemical species in the plasmas. Finally, an example of application of the GAD is presented: it is investigated the effect of plasma irradiation on the growth of microalgae. 

 

The text is well written, but for some minor mistakes 

 

* Lines 116-117 are highlighted in yellow. 

* Lines 129-133 are a duplicate of 124-128.

* At lines 216-219 the symbol "@" appears several times, instead of "+/-" 

* Lines 224-227 are a note/reminder for the authors themselves, not part of the main text.

 

Other comments:

* The first part of the document (lines 32-51) provides a nice introduction to GAD plasmas applications. The part between lines 51 and 59 is more confused, though. At this stage, it is not clear the scope of the informations provided there by the authors, they look like a set of scattered facts assembled together without a clear rationale.   

A similar comment applies to lines 68-92. The paragraph from line 60 is devoted to a discussion of the usage od Optical Emission Spectroscopy to determine the chemical composition of plasmas. A general introduction is fine, but after that there appears a long  enumeration of seemingly scattered results. I wonder what is its point.   

 

* Throughout the whole text, the authors employ frequently the verb "demonstrate". It is maybe just a matter of taste, but I do not feel this verb is appropriate, since it is used in connection with purely empirical facts.  

 

After these amendments, I think that the paper may be published

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript presents a new setup for generating the gliding arc plasma discharge, which is applied to the activation of the BG-11 medium. Detailed spectroscopic analyses of the plasma species during the air plasma discharge are performed, and the influences of applied voltage on the plasma discharge is investigated. It is confirmed that the air plasma treatment can effectively modify the concentration of a range of plasma-related components in BG-11 medium, in addition to the pH value and conductivity. The work is suitable for publication if authors can address my following comments.

1.           “The air was injected into the plasma reactor at room temperature from the top of the electrodes with a flow rate of 13.39 L/min and tangentially with a flow rate of 9.44 L/min before applying a high voltage.” Can authors specify why such flow rate is chosen and if other flow rates have been tested.

2.           “The two “knife-like” shaped electrodes with a length of 52 mm…”. Can authors provide photo or more detailed descriptions of the electrodes.

3.           “The voltage increases until the maximum value as the gliding arc column is elon gated. The arc breakdown occurs when the distance between the electrodes becomes too long and applied electric field is too low to sustain the discharge”. It is suggested to use more technical plasma discharge theory to rephrase the statement. E.g. Townsend discharge, Paschen’s law, etc.

4.           “The increase in current values versus time with expansion of arc could be due to fact that the voltage increases faster than the resistance between the electrodes.” The statement is interesting, can authors provide more evidence to support this argument?

5. The analyses of emission spectra and plasma species is very well performed. Do authors have plan to use 0D plasma chemistry simulation model, e.g. ZDplaskin to develop further understanding of the discharge properties.

6. “The first significant change during the plasma treatment was the increase of the temperature in the medium”. Does the medium temperature saturate at longer time scales, which does not seem to be the case in fig.10(a).

7.           “The effect of increasing processing voltage was also observed on the conductivity values” Is the conductivity change related to the change of certain chemical components after plasma treatment, can author give more explanations on this observation?

 

Author Response

Please see the attachment.

Author Response File: Author Response.docx