Electric Analysis of the Maritime Application High-Frequency Magnetohydrodynamic Thruster

Round 1

Reviewer 1 Report

This manuscript presents a series of results obtained from the experiment and simulation of magnetohydrodynamic thruster. The concept of engine is quite hopeful as a future thrusting device in maritime operations. Nevertheless, this manuscript is recommended to be rejected as an academic article for the following reasons:

(1) The purpose and method of conductivity measurement should be described in more detail in the section 2.1.

(2) The conductivities listed in Table 1 are shown also in Figures 1 and 2. The same data should not be shown multiple times unless it is required.

(3) This manuscript shows only disorderly the results of the measurements and computer simulations that have been already obtained. It is almost apparent that this study had not yet completed.

(4) Captions of figures should be written in more detail.

(5) Experiment and simulation should be designed so that results from these can be integrated into scientific or technical conclusions. This research attitude is collapsed in this study.

This manuscript should be checked towards a better English writing.

Author Response

This manuscript presents a series of results obtained from the experiment and simulation of magnetohydrodynamic thruster. The concept of engine is quite hopeful as a future thrusting device in maritime operations. Nevertheless, this manuscript is recommended to be rejected as an academic article for the following reasons:

(1) The purpose and method of conductivity measurement should be described in more detail in the section 2.1.

Author response: Thanks for your comment and of course, there is necessary to clarify the purpose of measurement clearly for a more understandable paper. The authors add the description in section 2.1. As to the method, the content has already been illustrated in the sentences in the following several lines. Thanks for your kind reminder.

Author action:

I add the sentences in section 2.1 to clarify the purpose of conductivity measurement: "

Research in [11] describes the phenomenon that AC performs the different production of electrolysis in some electrolytes to the DC. It is reasonable to deduce the variance impedance responses in cases of DC and AC. The conduction electrolyte's total power loss comprises the conduction and electrolysis losses. The conductivity measurement of the electrolyte thus needs to avoid the participation from the electrolyte. "

And the method was described in the later sentences already: "The impedance of solutions is measured at sinusoidal AC 0.5V peak voltage from 10kHz to 1.2MHz for the frequency range of the active switches in power electronics. The data measurement was conducted by a long and narrow tube, with dimensions in 960mm effective length and 17mm inner diameter applying the 218mL of 500mL solution. The solution's high resistance could help mitigate the impact of measurement wire impedance."

 

 

(2) The conductivities listed in Table 1 are shown also in Figures 1 and 2. The same data should not be shown multiple times unless it is required.

Author response: The figures were presented for the intuitive demonstration. Now the figures are deleted to streamline the paper structure.

Author action:

Figure 1, 2 were deleted.

 

 

(3) This manuscript shows only disorderly the results of the measurements and computer simulations that have been already obtained. It is almost apparent that this study had not yet completed.

Author response: Conductivity measurement is one of the contributions that provide the very practical data for the researchers. As mentioned in the introduction, the data is absent in the existing works. It also provides evidence of the AC advantages, those which the high-frequency operation leads to lower conduction loss.

The research on the maritime MHD engine is a new frontier. The impact of the electrodes' material is unknown. The comparison of Table 3 shows that Aluminium is optimal among Aluminium, stainless steel and Zinc.   Simulations of the ferrite and coil highlight the optimal design in "Figure 7. (c)" enclosed ferrite type with 5mm ferrite block type.

Author action:

1. Modify the sentences in "6. Conclusion" to highlight the measurement contribution: "The conductivity of the solution rose with increasing frequency, featuring the advantages of the AC."

 

2. Modify the last paragraph and add some sentences in "2. Frequency Response of Conductive Solution with the Metallic Electrode".

Content is "In a word, the higher frequency can mitigate the voltage drop on the imaginary impedance of the electrode interface to the electrolyte, decreasing the solution resistance energy loss. Also, the power consumption of the electrolysis can be mitigated. Among the materials of Al, stainless steel and Zn, the Al has the lowest energy consumption on the electrolysis, stainless steel is middle, and Zn wastes the most. Al also states the least equivalent capacitance in the study, whilst stainless steel occupies the highest. As to the conductivity, the three material performs very similarly when the voltage is higher than unity."

 

3. Simulation of the magnetic coil performances is time-consuming work. Theoretically, the higher thickness of the ferrite and the layers of the coil are better. But it simultaneously takes heavier weight, bulky size and expensive, with low "marginal revenue". The simulations are to figure out the characteristics of all magnetic field generation designs.

 

 

 

(4) Captions of figures should be written in more detail.

Author response: Thanks for the helpful comment. Now the captions are revised and explained with more detail. Figure 3 (a) has been replaced, with a legend in the Figure. Caption of it is updated. Figure 4 and Figure 5 are provided with more explanation.

Author action:

Figure 3 caption updates to:" Figure. 3 Resistance modelling of the electrolyte and electrolysis: (a) one of the testing rigs for the modelling of the conductive solution equivalent electric parameters; (b) the electrical circuit model of the conductive solution for MHD applications. "

Figure 3 (a), updates with legend.

 

Figure 4 adds the text:" with ferrite blocks beside to generate the magnetic field inside the duct for propulsion."

 

Figure 5 adds the text:" with ferrite blocks on top and beneath to generate the magnetic field inside the duct for propulsion."

 

Figure 6 adds the variables in the caption:" Figure 6. Dimensional parameters a, b, c, d, e of the MHD thruster duct and coil: (a) Pancake winding coil type; (b) saddle type. "

 

Figure 9. updates to:" Picture of the proposed AC MHD thruster prototype being immersed in the KCl standard salinity solution for the experiment. The magnetic coil is a pancake winding 1-layer type. "

 

Figure 10 updates to:" Coil installation of the prototype, grey blocks are the ferrite, outside tubes for series connection of the electrodes and the coil on top and beneath. "

 

 

Figure 15 updates to:" The proposed AC MHD thruster is pushing out the fluid with the ink indicator."

 

 

 

(5) Experiment and simulation should be designed so that results from these can be integrated into scientific or technical conclusions. This research attitude is collapsed in this study.

Author response:

The authors do not accept the notion of attitude collapse of simulation and experiment design in arriving at scientific and technical conclusions. The simulation of the magnetic coil gives the magnetic field value and the coil inductance. The measurement of the inductance varies little from the simulation results, hence, verify the B. The measurement result of the solution in different metal plate materials guides the resistance estimation for the drive circuit design. Comparing the simulation results of the E to the measurement value of Z_CD proves the high confidence of the simulation.

The circuit design follows section 4, and experimental results of the electric waveforms verify the theory, and the results of the KCl solution flowing velocities have been recorded. The overall process validates the operation and quantitative design of the AC MHD thruster. The authors are proud to submit the research works and provide new sight, new data and new research areas to the peer.

 

 Author action:  

Add the design flow chart to elaborate the development procedure to build the prototype.

 

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Please see attached PDF for comments and suggestions for authors.

Comments for author File: Comments.pdf

Author Response

Reviewer 2:

This article investigates the solution parameters, and the new coil design of the MHD thruster and the AC operation and electric drive with the Lorentz force analysis demonstrated. At last, the verification experiment is interpreted by the prototype to display the electric operation detail. Overall, the research paper is good; good jobs from authors! I recommend the paper for publication. However, the authors will have to address several concerns and issues before it can be successfully published.

1. The title might be too lengthy that it loses its focus. Maybe the authors can consider a shorter title.

Author response: Thank you for your positive comment! This research is quite a pioneer in the new area lacking clear theory, solid and abundant data. The exploration is challenging but interesting.

The title now is shortened, integrating the concept together in words "Electric analysis of."

Author action:

Change the title from "High frequency resonant circuit and laboratory testing salinity solution analysis of the Maritime Application Magnetohydrodynamic Thruster" to "Electric Analysis of the Maritime Application High-Frequency Magnetohydrodynamic Thruster."

 

 

2. No doubt that the abstract is well written, but it is too quantitative. Authors should reflect some of their presented results in the abstract aiming at addressing/highlighting the research gaps and important contributions, with relation to practical applications.

Author response: The comment is helpful to highlight our contribution. The abstract is updated with the find out now.

Author action:

Update 2 sentences (highlighted) in the abstract:" A Magnetohydrodynamic (MHD) thruster is the next-generation electric jet engine for maritime applications. It eliminates the moving mechanical components that make the noises and brings physical to the sea creatures. This paper finds the Aluminium performs higher conductivity and less capacitive value of the KCl solution than the 316 stainless steel and Zinc. Further, the AC operation can mitigate the power loss on the electrolysis and power loss on the water. The new optimal coil design with the enclosed type ferrite layout of the MHD thruster is addressed by the simulation study. The AC operation and electric drive with the Lorentz force analysis will be demonstrated. At last, the verification experiment will be interpreted by the prototype to display the electric operation detail. "

 

 

3. The originality/novelty is not really highlighted in Section 1 Introduction. The written paragraph

focused more on what is not done, and thus will be conducted. The paragraph should elaborate

more the importance, and addresses/highlights the research gaps and contributions, with relation

to practical applications (give examples).

Author response: Stressing the contribution is vital for all the researches. The authors agree that the elaboration of the research gap was weak. The abstract and the section of introduction now is updated to presents the innovations more explicitly 

Author action:

 

Delete the sentences of the MHD technology in non-seawater applications which distract the focus of the throughout section.

 

Update the end of the first paragraph to emphasize the benefits of AC operation MHD thruster.

 

The second paragraph is rewritten, to elaborate the electric aspect of the MHD thruster clearer, and highlight the research gap at the end.

 

Some sentences of the third, fourth and fifth sentences are rewritten for linguistic improvement.

 

 

 

4. In 3. Magnetic Coil Structure and Study of Simulation, the authors can consider discussing more

on the simulation details.

Author response: Thanks for the comment. The paragraph now supplements more detail. The changes of the last two paragraphs in this section are highlighted below.

Author action:

" High frequency operation reduces the resistance of the solution, observed by the Table 3. That can achieve higher energy efficiency, therefore to operate the AC MHD thruster at a high frequency with the Litz wire. The wire has a cross-sectional area of 12.25mm²_, and the winding of saddle-type stacks to the same height as the acrylic frame. For pancake coils, the plane area all filling by the wires is preferred over the hollow layout, for the larger B. Assume the ferrite has a relative permeability of 3300, and the saturation value is 0.5T. The B-H curve is considered a linear relationship. The nonlinear residual set at 0.001, refinement is 30% and the minimum number of passes is 3.

Table. 4 shows the simulation results of 2 excitation currents, indicating the average magnetic field densities of the corresponding coil designs. The saddle type performs slightly more advantage than the pancake coil when the a is 0, no more than 10% in three dimensions of b. But the situation reverses when a=5, meaning the ferrite starts to enclose the duct. The pancake coil has 17% higher value in 21A and 18% in 30A than the saddle coil. By comparing the results of No.3, 4 and 5, the thin enclosed ferrite features the optimal layout in the ferrite weight and B value trade-off. The values of B generated by the saddle coil have no or little variance but the mass of ferrite! The field distribution characteristics of the simulations are shown in Figure 5."

 

 

 

5. In 5. MHD Thruster Experimental Results, the authors should include a table showing the

percentage deviations between the experimental and numerical results for clarity.

Author response: In fact in this stage, only the deviation of the resistance estimation can be conducted by the measurement, and the corresponding value has already been updated in below.

The magnetic coil proposed was implement, and the value acquired by the simulation. And that of the frequency determined by the inductance and capacitance is not necessary.

Author action:

Update the sentences in section 5:" . The testing solution's temperature is 23℃, and the simulation R_CD using the S=35 conventional seawater standard data is 1.26 Ω, but the measurement of the experimental liquid is 1.1Ω. The conductivity ratio of the standard to the 10kHz measurement value in Table 1 at 20 ℃ is 0.83, namely the 10kHz resistance should be the 0.83 times of the estimation at 20℃. The conductivity ratio is 1.1/1.26=0.87, with 5% variance inaccuracy in resistance estimation. "

 

 

 

 

 

6. From Section 2 to 5. Results Analysis and Discussion, the authors deserve compliments for the

large amount of nice data generated; excellent job authors! However, the authors should attempt

to highlight as much as possible (which currently missing) what exactly is the originality/novelty of their results, in comparison to some existing literatures. This allows readers to differentiate their

research from others, and highlight their important contributions. This will add significance to the

section greatly.

Author response: For the sections 2, 3 and 5, paragraphs are updated to highlight the research gap. 

For section 4, since there has no any AC MHD thruster, the topology is new.

 

Author action:

In section 2, add last paragraph to stress the contribution:" In a word, the higher frequency can mitigate the voltage drop on the imaginary impedance of the electrode interface to the electrolyte, decreasing the solution resistance energy loss. Also, the power consumption of the electrolysis can be mitigated. Among the materials of Al, stainless steels and the Zn, the Al has lowest energy consumption on the electrolysis, stainless steel is middle and Zn wastes most. Al also states the least equivalent capacitance in the study, whilst the stainless steel occupies the highest. As to the conductivity, three material performs very similar when the voltage is higher than unity."

 

In section 3, the sentences in the last paragraph notions the optimal design:" The pancake coil has 17% higher value in 21A and 18% in 30A than the saddle coil. By comparing the results of No.3, 4 and 5, the thin enclosed ferrite features the optimal layout in the ferrite weight and B value trade-off. The values of B generated by the saddle coil have no or little variance but the mass of ferrite soar! "

 

For section 4, no extra modification for this comment

 

For section 5, add the illustration highlighted in yellow to compare the proposed frequency variation conductivity measurement has 95% accuracy of the 10kHz resistance measurement:" C_r is 758nF to resonate with the L_p, and L_c at 9.96kHz. The 10kHz f_s ensure the inductive operation of the drive circuit. R_p is 0.2Ω. The testing solution's temperature is 23℃, and the simulation R_CD using the S=35 conventional seawater standard data is 1.26 Ω, but the measurement of the experimental liquid is 1.1Ω. The conductivity ratio of the standard to the 10kHz measurement value in Table 1 at 20 ℃ is 0.83, namely the 10kHz resistance should be the 0.83 times of the estimation at 20℃. The conductivity ratio is 1.1/1.26=0.87, with 5% variance inaccuracy in resistance estimation. "

 

 

7. In 6. Conclusions, the link between the research outcomes and the importance of the research to

actual applications can be established in the conclusion section.

Author response: Some sentences are updated for the conclusion.

Author action:

 

Add the decisive tone sentence:" The measurement results indicate the fact that the conductivity of the solution rose with increasing frequency, featuring the advantages of the AC to have the lower power loss on the conduction loss. "

 

Add the decisive tone sentence:" Aluminum is the optimal electrode material in the electrical aspect that has the lowest parallel capacitance and resistance of the electrode-electrolyte interface."

 

Add the decisive tone sentence:" pancake coil……, to provide a higher power density for the MHD thruster."

 

Add one more sentences at the end of the paper:" The comprehensive analysis of the marine AC MHD thruster, covering thorough simulation, measurement and the experiment about the salinity-conductivity conversion, coil design, fluid equivalent circuit and thruster drive design, and real fluid pushing test are interpreted."

 

 

 

8. This investigation is related to Magnetohydrodynamic (MHD) thruster, which is definitely of interest for a wide range of applications ranging from medical [a], chemistry and biology [b, c], and micro- and nanofluidics [d-f]. Statement of the importance of current work can be discussed along with the suggested references to further enhance the introduction section, as well as strengthen the significant and novelty of the current research:
9. Gregory, et al., 2015. Magnetohydrodynamic-driven design of microscopic endocapsules in MRI. IEEE/ASME Transactions on Mechatronics, 20(6), 2691-2698.
10. Zeeshan, et al., 2018. The sustainable characteristic of bio-bi-phase flow of peristaltic transport of MHD Jeffrey fluid in the human body. Sustainability, 10(8), 2671.
11. West, et al., 2002. Application of magnetohydrodynamic actuation to continuous flow chemistry. Lab on a Chip, 2(4), 224-230.
12. Bau, et al., 2022. Applications of Magneto Electrochemistry and Magnetohydrodynamics in Microfluidics. Magnetochemistry, 8(11), 140.
13. Lim, et al., 2021. Electroosmotic Flow Hysteresis for Fluids with Dissimilar pH and Ionic Species. Micromachines, 12(9), 1031.
14. Lim, et al., 2023. Effect of Microchannel Diameter on Electroosmotic Flow Hysteresis. Energies, 16(5), 2154.

 

Author response: The comment increasing the quality of the research is welcome! Now the big picture of the technology of the MHD is enriched.

Author action:

Update a current development paragraph for the MHD technology:" Rather the marine propulsion, the current development of the MHD covers the medical [23], chemistry and biology [24], [25], and micro- and nanofluidics [26], [27], [28]. The papers attempt to accelerate the micro-robot or the particles in the blood. Analysis of the Newtonian and non-Newtonian flow were illustrated. A new MHD thruster was proposed to feed the tritium breeding blankets, but the coolant raises a deep concern in that application [29]. The MHD thruster has a steel wall and can transfer molten lithium at a very low speed, even at several hundred temperatures, with the helium coolant system. A similar fusion breeder MHD thruster has been studied [30], in which the magnetic field in the duct has been investigated, and the maximum field density is 5T. "

 

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Manuscript is worthy and interesting to be considered for possible publication after incorporated the minor revision given below:

 

The title of the manuscript "High-Frequency Resonant Drive Circuit and Laboratory Test- 2 ing Salinity Solution Analysis of Maritime Application Magne- 3 tohydrodynamic Thruster" is required to change to portrayed the novelty and contribution in brief.

Authors are suggested to review the abstract again by insrted the qualitative as well as quantitative inferences. 

Introduction need revisions, The introduction section is segmented into introduction, related studies, problem statement, Significance, contribution and organization for better flow of information.

 

 

The methodology section should be provided with pseudocodes, process flow diagram, architecture, and mathematical details. Please also provided the necessary parameter settings and configrations as well.

Workflow for the proposed procedures for the presented domain should be inserted with description of the process flow structure for each step.

 Some terms should be defined at the first used for better understanding

Finally, feq other simulation/experimental examples should be taken in order to draw concrete inferences.

Experimentation is very limited, please provide more simulation results.

Reference should be given on the template of MDPI journal style.

Improve the linguistic quality.

No any

Author Response

Reviewer 3:

Manuscript is worthy and interesting to be considered for possible publication after incorporated the minor revision given below:

 

The title of the manuscript "High-Frequency Resonant Drive Circuit and Laboratory Test- 2 ing Salinity Solution Analysis of Maritime Application Magne- 3 tohydrodynamic Thruster" is required to change to portrayed the novelty and contribution in brief.

Author response: The authors agree that the title was too long. Now it is updated in a shorter way.

Author action:

Update the title to:" Electric Analysis of the Maritime Application High-Frequency Magnetohydrodynamic Thruster."

 

 

 

Authors are suggested to review the abstract again by inserted the qualitative as well as quantitative inferences. 

Author response: The abstract now is updated to boost the impact.

Author action:

Update the abstract, adding the highlighted content:" A Magnetohydrodynamic (MHD) thruster is the next-generation electric jet engine for maritime applications. It eliminates the moving mechanical components that make the noises and brings physical to the sea creatures. This paper finds the Aluminium electrodes performs higher conductivity and less capacitive value of the KCl solution than the 316 stainless steel and Zinc in MHD applications. Further, the AC operation can mitigate the power loss on the electrolysis and power loss on the water. The new optimal coil design with the enclosed type ferrite layout of the MHD thruster is addressed by the simulation study. The AC operation and electric drive with the Lorentz force analysis will be demonstrated. At last, the verification experiment that push the KCl solution at 3cm/s will be interpreted by the prototype to display the electric operation detail. "

 

 

 

Introduction need revisions, The introduction section is segmented into introduction, related studies, problem statement, Significance, contribution and organization for better flow of information.

Author response: Authors organized the introduction again, modified the ambiguous sentences, provided more background information and emphasize the contributions. 

Author action:

Add the sentences in introduction:

 

"The gases consist of chloride, hydrogen, oxygen and other material that impose poison and explosion hazards to the vessel that limits the wide applications. In this paper, the authors implement the alternating current (AC) to the MHD thruster and cancel the defects of the DC as aforementioned. "

 

"The electrolysis, impact of B field, Lorentz force acceleration and ship moving feature the MHD thruster as a complicated inter-discipline system involving electrical, chemistry, centropy generation, and fluid dynamics [12], [13]. For the electrical aspect, the MHD system ranges the drive circuit for the propulsion system, the B field generation design, the equivalent resistance model of the seawater involving the electrolyte conduction loss, electrolysis loss, parameters of the electrode and electrolyte interface and the energy consumption of the propulsion. "

 

"Along with the experiments and measurement of this paper, the electrolysis gas emission activities and its dissipation were observed and recorded with the quantified conditions. This phenomenon is presented in section 2, providing an intuitive understanding of AC superiority."

 

"Hence, in this paper, the comparison study of the simulation on the magnetic component layouts will be displayed to provide a solid reference and optimal layout for the AC MHD thruster. "

 

" Rather the marine propulsion, the current development of the MHD covers the medical [25], chemistry and biology [26], [27], and micro- and nanofluidics [28], [29], [30]. A new MHD thruster was proposed to feed the tritium breeding blankets, but the coolant raises a deep concern in that application [9]. The MHD thruster has a steel wall and can transfer molten lithium at a very low speed, even at several hundred temperatures, with the helium coolant system. A similar fusion breeder MHD thruster has been studied [10], in which the magnetic field in the duct has been investigated, and the maximum field density is 5T."

 

 

 

The methodology section should be provided with pseudocodes, process flow diagram, architecture, and mathematical details. Please also provided the necessary parameter settings and configrations as well.

Workflow for the proposed procedures for the presented domain should be inserted with description of the process flow structure for each step.

Author response: Thanks for a good suggestion, now a flowchart is attached.

Author action:

A flowchart now has been updated in the section 5.

 

 

 

 Some terms should be defined at the first used for better understanding

Author response: Terms are now well defined.

Author action:

Add a sentence"……R_CD, resistance between the electrodes now."

 

Add words:" electric field (E)"

 

Add "standard" before the standard of practical standard salinity PSS-78, :" . But the standard PSS-78 [16] defined…… "

 

 

 

Finally, feq other simulation/experimental examples should be taken in order to draw concrete inferences. Experimentation is very limited, please provide more simulation results.

Author response: We add one more simulation of the circuit in Figure 11, for the more comprehensive and convincing illustration. To clarify, the simulation covers the magnetic field, electric field, resistance estimation of the fluid. Experiment comprises the measurement of the fluid resistance, electric component parameters and the operation of the circuit, as well as the fluid velocity.

Author action: add the simulation of the circuitry operation simulation in Figure 11.

 

 

 

Reference should be given on the template of MDPI journal style.

Author response: The references have been modified by the authors using the Endnote and Zotero, but it just causes a mess: the numbers are wrong, indicating the "INVALID CITATION" in reference.

    The authors noticed the citation would be added by editorial staff during production. Hence, now the authors submit the Word file with the .pdf, ensuring the corrective presentation.

 

Author action:

The references remain not changed.

 

 

 

Improve the linguistic quality.

Author response: Thanks for the kind reminder, Now the text is updated.

Author action: Revise the text and correct the typo mistakes. Some sentences are modified.

 

 

Author Response File: Author Response.pdf

Reviewer 4 Report

*) The introduction is essentially devoted to the state of the art of the problem under study.  However, there is little highlighting of the contributio of the submitted paper which in only one sentence at the end of the Section. Please, emphasize your contribution to the problem. 

*) In the text there are some typos that shoulld be remove.

*) Please, make all captions self-explanatory.

*) For non original mathematical formula at least one relevant reference should be associated.

*) You wrote: "The measurement results are displayed in Table 1 and Figure 1, Figure 2. From 10kHz 115 to 1.2MHz, it is obvious the conductivities of three solutions in five temperatures rise with 116 the A.C. frequency. In which the range from 10 to 20℃, higher temperature features 117 higher conductivity." Is there a theoretical basis? Please, if possible, specify.

*) Please, if possible, improve the quality of Figure 3.a.

*) You wrote: "To achieve higher energy efficiency, it is recommended to operate the AC MHD 224 thruster at a high frequency." Why?

Author Response

Reviewer 4:

 

*) The introduction is essentially devoted to the state of the art of the problem under study.  However, there is little highlighting of the contribution of the submitted paper which in only one sentence at the end of the Section. Please, emphasize your contribution to the problem. 

Author response: The authors absolutely agree the importance of marking the contribution. Now the section of introduction is updated for explicit understanding.

Author action:

Add sentences in the first paragraph:" The gases consist of chloride, hydrogen, oxygen and other material that impose poison and explosion hazards to the vessel that limits the wide applications. In this paper, the authors implement the alternating current (AC) to the MHD thruster and cancel the defects of the DC as aforementioned."

 

Add sentences in the second paragraph:" Along with the experiments and measurement of this paper, the electrolysis gas emission activities and its dissipation were observed and recorded with the quantified conditions. This phenomenon is presented in section 2, providing an intuitive understanding of AC superiority."

 

Add sentences in the third last paragraph:" Hence, in this paper, the comparison study of the simulation on the magnetic component layouts will be displayed to provide a solid reference and optimal layout for the AC MHD thruster. "

 

 

*) In the text, there are some typos that should be removed.

Author response: Sorry for the mistake. The text is revised and be updated to the correct form.

Author action: Correct the typo mistakes, and rewrite some sentences for easy understanding.

 

 

 

*) Please, make all captions self-explanatory.

Author response: Thanks for the effective advice. Now the captions provide more detail.

Author action: Update all captions to presents the idea clearly.

 

 

 

*) For non original mathematical formula at least one relevant reference should be associated.

Author response:

Author action: Cite the [26] and [27] for equations (6) and (8).

[26]	A. K. Garg, Classical Electromagnetism in a Nutshell, Princeton: Princeton University Press, 2012.
[27]	L. S. Lerner, Physics for Scientists and Engineers, Boston: Jones and Bartlett, 1996.

 

 

 

*) You wrote: "The measurement results are displayed in Table 1 and Figure 1, Figure 2. From 10kHz  to 1.2MHz, it is obvious the conductivities of three solutions in five temperatures rise with  the AC frequency. In which the range from 10 to 20℃, higher temperature features 117 higher conductivity." Is there a theoretical basis? Please, if possible, specify.

Author response: Yes. It is a standard in [16] of the paper, the standard salinity standard PSS-78: "The United Nations Educational, Scientific and Cultural Organization (UNESCO), Tenth report of the joint panel on oceanographic tables and standards, Sidney, B.C., Canada, 1981."

Also :" E. Lewis, "The practical salinity scale 1978 and its antecedents," IEEE Journal of Oceanic Engineering, vol. 5, no. 1, p. 3–8, 1980"

Author action:

Add the citation (highlighted) at the sentence :" The measurement results are displayed in Table 1. From 10kHz to 1.2MHz, it is obvious the conductivities of three solutions in five temperatures rise with the AC frequency. In which the range from 10 to 20℃, higher temperature features higher conductivity, meets the tendency of  [16]."

 

 

 

*) Please, if possible, improve the quality of Figure 3.a.

Author response: A helpful suggestion. Now it is enlarged.

Author action: Enlarge the Figure 3.a.

 

 

 

*) You wrote: "To achieve higher energy efficiency, it is recommended to operate the AC MHD thruster at a high frequency." Why?

Author response: From the Table 3 that the resistance and equivalent capacitance between the electrodes drops with the increasing frequency, the power loss on the thermal dissipation can thus be saved.

Author action:

Update the sentence to "High frequency operation reduces the resistance of the solution, observed by the Table 3. That can achieve higher energy efficiency, therefore to operate the AC MHD thruster at a high frequency with the Litz wire."

 

 

 

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

To bring his manuscript to an acceptance, comparing experimental and simulated results, and if possible, plotting these two kinds of results on same graphs, should be indispensable. This study should validate the simulation results, that is, discuss whether the "simulated" results really simulated what occurred in the experiment. 

English writing should be brushed up more.

Author Response

Thanks for your precious comment for the authors to improve the research paper quality. The simulation comparison to the experiment in a single picture is now updated in Figure 13. The synchronization of the Ir and VCD, the inductive operation and the ZVS and the 90% accuracy of the I_r estimation all comply with the electric analysis of the proposed drive.

Author action:

We have added the paragraph from line 412 to the 421 in the MHD Thruster Experimental Results section.

Add the comparison figure as Figure 12.

Some sentences are improved more succinctly.

 

Reviewer 2 Report

The authors have well-addressed the comments and suggestions. The paper is now ready for publication. Good job, congrats authors!

Author Response

Thank you for your review and the authors are excited to see the publication

Reviewer 3 Report

No further comments

Author Response

Thanks for your review and the good suggestions raised before

Round 3

Reviewer 1 Report

I checked the revisions. It might be said that these bring this manuscript to a publishable article.

English writing should be edited again before online puplication.