Inlet Gap Influence on Low-Frequency Flow Unsteadiness in a Centrifugal Fan

Round 1

Reviewer 1 Report

The author mainly studies the unsteady low-frequency characteristics of the volute-free centrifugal fan used in HVAC system, which is of great significance to reduce the influence of HVAC system on IEQ. The content of the article can be modified to a higher level, so the following suggestions are put forward.

1.     The contents of lines 46-47 overlap with those of lines 40-44, so it is suggested to modify them.

2.     Section 3.2 verifies the model. Only one set of data is given. Please supplement the data for comparison and verification.

3.     In Section 5.2, the purpose of the content is not clear, the logic of the connection of the content is unnatural, the data is insufficient, and only one phenomenon at a time is analyzed. Please clarify the research purpose, supplement the data and improve the conclusion.

4.     The reference of BLE, BTE and BPF in Section 5.2 is not clear. Please explain.

5.     Section 5.3, line 288-289 sets a monitoring point to monitor the speed change rule. Please explain the location and reason of the monitoring point.

6.     In Section 5.3, the velocity distribution in different areas of the annular gap is quite different, so only one monitoring point is set for analysis, which is not representative. Please supplement the data.

7.     This paper mainly studies the distribution of pressure and velocity parameters in the flow field. Please add the unsteady low-frequency characteristics of the volute free centrifugal fan.

Author Response

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Reviewer 2 Report

Review report for “Inlet gap influence on low-frequency flow unsteadiness in a centrifugal fan”, aerospace-1959110

This manuscript researches the unsteady low-frequency characteristics in a voluteless low-speed centrifugal fan operating at a high mass flow rate by delayed detached eddy simulation (IDDES) method. Some points of this paper need revise:

1.     The language of this paper needs revise for fluency, concise and accurate, while maintaining the key information. Besides, the discussion of the research findings should be logical.

2.     Introduction part:

It is suggested to rank the references with chronological order. Besides, the discussion of references in the introduction part is suggested to add some proper comments to elaborate the significance or the progressive relationship of the researches. Please revise the introduction accordingly.

3.     Numerical methodology

Please move “All simulations are performed using the commercial software STAR-CCM+ [28]” to the front portion of the Section 3.1.

4.     Section 5: Results and discussions

The analysis in Section 5 needs revise to become more concise while maintaining the key research findings. Besides, the analyses in Section 5 needs more depth (this can be achieved by adding quantitative analysis of parameters in figures and tables) and elaborate the relationship between each important finding if possible.

Author Response

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Reviewer 3 Report

The article entitles ‘Inlet gap influence on low-frequency flow unsteadiness in a centrifugal fan’ presents a numerical investigation performed by using improved delayed detached eddy simulation (IDDES) on the unsteady low-frequency characteristics in a low-speed centrifugal fan operating at a high mass flow rate. The authors mainly study the unsteady low-frequency characteristics of the volute-free centrifugal fan used in HVAC system to reduce the influence of HVAC system on IEQ.

The background was discussed with references covering the current research outcomes, including the authors’ previous publications.

The purpose of this study was clearly addressed with solid knowledge of the methodological development and technical outcomes.

 The following suggestions are provided:

1.      In section 3.2 authors verify the model presented using only one set of data, it can be improved considering supplement data for comparison and verification.

2.      The research purpose in Section 5.2 can be improved, the link of the content is not entirely clear. Only one phenomenon at a time is analyzed, it is suggested to use more data and improve the conclusion.

3.      It is suggested to explain the location of the monitoring point described in Section 5.3.

The overall results were significant, presented and discussed properly, and the conclusion was addressed sufficiently clearly. The paper is well structured, written fluently with high quality plots and figures.

In my opinion, this is a good quality paper, and I recommend accepting.

Author Response

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Round 2

Reviewer 2 Report

Dear author,

For this version, it is suggested to revise the "AS people spend most of their time  up to 90 %[1], indoor environmental quality (IEQ) is critical to the quality of life" to "Since that we spend the majority of our time up to 90 %[1], indoor environmental quality (IEQ) is important to the quality of life" in the introduction part.  This is a good research work.

No other comments.  

Author Response

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