Design of Electric Supercharger Compressor and Its Performance Optimization

Round 1

Reviewer 1 Report

Dear Authors:

Thank you for the opportunity to review your article. The comments below should improve your work before it is published.

The reviewed article deals with construction and scientific-research investigation of power optimization concerning centrifugal compressor installed in the electric turbochargers, which are applied in two-stroke engines used as driving units of the small Unmanned Arial Vehicles (UAV). The chapter “Introduction” comments 26 references of the appropriate literature sources. The theoretical background, necessary for realization of the planned research work, is summarized in the second chapter, which is focused on numerical simulation and computational modeling of centrifugal compressor. The own creative scientific-research work is presented in the third chapter titled “Study of the influence of relevant parameters on the performance of centrifugal compressors”. In my opinion, the article offers interesting theoretical results obtained in this specific investigation area and it is suitable for publishing in the given professional journal. However, I recommend to supplement it according to my following comments or suggestions:

- There is also important and interesting, within the whole context of the article, the chapter 4 “Experimentation” and just for that reason it requires to be elaborated at least on a slightly wider extent, i.e. to make it more descriptive and explanatory regarding the experimental measurements and obtained results,

- I recommend to add into the article some illustrative photos of such UAV that are powered by the engines equipped with electric turbo-chargers containing the investigated centrifugal compressors. I consider such photos would be interesting for the readers.

Yours sincerely

Your reviewer

Author Response

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Reviewer 2 Report

In this paper, the influence of the impeller and diffuser parameters on the compressor performance were investigated. The results found that increasing the number of impeller blades will decrease the low-speed zone range at the compressor exit, resulting in a decrease in entropy and an increase in compressor efficiency. A appropriate increase in the impeller's backbend angle enhances its efficiency and pressure ratio. However, a continuous rise of backbend angle will reduce the exit 440 airflow deflection angle and intensify the airflow separation phenomenon in the flow 441 channel. These factors result in an increase in inefficiencies. Increasing the relative width 442 of the impeller exit decreases the relative speed of the impeller and increases pressure 443 expansion, thereby amplifying the compressor's pressure ratio.

1. The abstract should be summarized again and put emphasis on the new findings, the primary findings of the paper should be presented briefly.

2. More information about mesh independence analysis should be added in the 2.3 Simulation analysis.

3. The value range of Figure 3, Figure 6, Figure 7, Figure 8, Figure 10, Figure 11, Figure 13, Figure 14, Figure 16 and Figure 17 should keep in the same, which can easy to compare the difference of different simulation results.

4. More information about the test bench should be added in the 4. Experimentation. The test instruments and their measurement accuracy should be provided, and a system error analysis of the test bench may help for the publication strictness.

5. Figure 4, Figure 7, Figure 8, Figure 11, Figure 14 and Figure 17 are very blurry so that they cannot be read easily, the author is suggested to edit it clearly.

6. The authors should briefly demonstrate why they choose the several values (7x7, 6x6 and 8x8) as impeller blades.

Minor editing of English language required

Author Response

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Reviewer 3 Report

The authors design a supercharger using numerical methods. The internal flow is simulated. Finally, the experimental data of the compressor are shown. The comparison of the numerical and experimental results is not good.

* Primary concern is the novelty. There are many designs of centrifugal compressors in literature. Many researchgers reported the effect of blade numbers, splitter blades ... .

* The description of the numerical and design methodology is insufficient.

* There is no statements about surge and compressor choke limits chosen for the design.

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There are several references that seem to have nothing to do with the text. Reference [28], " Analysis of Craniocerebral Injury in Facial Collision Accidents", is cited for the numerical methodology. However, [28] does not contain any fluid dynamic simulations. Also reference [13], "Research on Dynamic Analysis and Experimental Study of the Distributed Drive Electric Tractor", has nothing to do with the text.

The authors state in line 117, "... the isentropic efficiency is greater than 0.8 ...". However, the value listed in Table 1 is 0.75.

In line 110, the authors state that nu tilda is the "pulsation velocity of turbulence". However, nu tilda is the Spalart-Allmaras variable! Please fix that. The authors should also reference to works using the Spalart-Allmaras turbulence model with this application, e.g. Semlitsch and Huscava (2022) "Shape Optimisation of Turbomachinery Components".

The authors state that the flow medium is air. Why do the authors model air as a real gas? Air should be modelled as ideal gas at this temperatures.

Please provide a full description of the numerical model! No numerical schemes have been specified. The turbulence boundary conditions are not stated. Which y+ values are obtained with the mesh?

Please improve the image quality of Figure 2. The mesh cannot be seen.

Several images show a single passage. Figure 2 show a full annulus mesh. What has been used, a single passage or a full annulus mesh?

Why does the Mach number in Figure 4 rise in the diffuser? The Mach number should decrease in the diffuser.

There centrifugal compressor in the experimental setup has a volute. The centrifugal compressor in the numerical study has no volute. How is it expected that the results are alike? - Please compare the experimental results to the numerical results directly. I do not see a good match of the results.

There are several language and spelling mistakes. Please fix them. - For the RANS equations descrition, it should be fluctuation quantities and not pulsation quanties. Please replace "pulsation" with "fluctuation". - In line 112, replace the comma with a dot.

Author Response

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Round 2

Reviewer 3 Report

There is still some information missing that others could reproduce the results. E.g. which value was set for the Spalart-Allmaras variable at the inlet?

The language errors are moderate. E.g. there are some typesetting errors in the caption of figure 19 "compre ssor".

Author Response

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