The Overall Design of Variable Diameter Ducted Fan in the Aircraft
Round 1
Reviewer 1 Report
Dear authors,
the paper faces an interesting topic suitable for the present journal.
Anyway I suggest the following points:
- the CFD simulations should be better detailed (boundary conditions, flow regime, numerical stability, solver);
- Figure 22 to be described in-depth;
- the title needs to be updataed including a reference to the application field (helicopter, aviation, etc...);
- which is the novelty of the research? To include well this aspect in the conclusions.
Author Response
Point 1: the CFD simulations should be better detailed (boundary conditions, flow regime, numerical stability, solver).
Response 1: A better-detailed CFD simulation is added on lines 114 to 123, including boundary conditions, flow regime, numerical stability, and its solver.
Point 2: Figure 22 to be described in-depth
Response 2: Figure 22 is better-detailed described on lines 359 to 367, including its formation mechanism and the trend of downloading effect in flight.
Point 3: the title needs to be updataed including a reference to the application field (helicopter, aviation, etc...);
Response 3: After discussion, the authors agreed that it is more appropriate to add “in the aircraft” as the application field of VDDF in the title.
Point 4: which is the novelty of the research? To include well this aspect in the conclusions.
Response 4: The novelty of the research is included well in the Discussion on lines 434 to 446, including the novelty of the research on application, calculation process, and mutual interference.
Author Response File: 
Author Response.docx
Reviewer 2 Report
A very interesting, extensive article solves a very topical issue „The overall design of variable ducted fan“.
The structural parameters of the variable diameter ducted fan(VDDF) were selected, for helicopter Z9, by an orthogonal experiment method.
Based on the momentum-element theory, the aerodynamic theoretical model of the disk was established.
A high level of article reduces some formal shortcomings and errors:
- -- The article lacks a reference to literature [20];
- -- Inconsistent form of literature presentation in references;
- -- Figures 21 and 24 incorrectly show the Mk N/m torque unit;
- -- Figure 22 does not indicate the x-axis;
- -- Row 353 incorrectly indicates the power kw, etc.
After you have fixed the deficiencies, I recommend that you publish the article.
Author Response
Point 1: The article lacks a reference to literature [20]
Response 1: The literature[20] is referred to in Table 2 previously. Now, the literature[20] is referred to on line 244 to make it more obvious.
Point 2: Inconsistent form of literature presentation in references
Response 2: The authors check the form of the literature presented in references by EndNote software and Aerospace template, and try our best to format the literature to match the template’s requirements. But there may still have some flaws because of the lack of information in some literature or types that are not mentioned in the template. For instance, literature[3] is a NASA report but the report style is not mentioned in the template, so authors refer to the format of MDPI in EndNote software.
Point 3: Figures 21 and 24 incorrectly show the Mk N/m torque unit
Response 3: The Mk N·m torque unit is revised in Figures 21 and 24.
Point 4: Figure 22 does not indicate the x-axis;
Response 4: The X-axis and Y-axis are added in Figure 22.
Point 5: Row 353 incorrectly indicates the power kw, etc
Response 5: The power unit kW is revised on line 373 and Figure 23.(the line number is changed because of the revise of the pervious manuscript)
Author Response File: Author Response.docx
Reviewer 3 Report
It is known that variable diameter of a rotor disk and a duct structured-fan of an aircraft ,i.e.,. Z-9 helicopter prototype, can improve the flight performance in both hovering, i.e., up-flying direction, and forward-flying direction. In the present study, the numerical-modelling of structural parameters of the variable diameter ducted fan(VDDF) are selected to simultaneously investigate the optimum design conditions of the structure parameters of the rotor disk and the ducked fan by using obtained parameters of an orthogonal experiment method. The V-22 tilt-rotor aircraft was the reference object for the modification of Z-9 helicopter prototype in this investigation. The aerodynamic theoretical model of the rotor disk is established based on the momentum-element theory and the structural parameters that can achieve the best efficiency in hover/propulsion directions. The momentum-element model and orthogonal experiment model are validated with the experimental results as well as with the calculated results from ANSYS CFD. The technique for order of preference by similarity to the ideal solution(TOPSIS) model is established to evaluate the quality of different design variables at different levels.
The design objective was to improve the flight performance, i.e., hover ceiling, cruise altitude, and cruise speed, hover efficiency(FW), propulsion efficiency(η) , after the Z-9 is equipped with a VDDF simulator, and the hover and forward flight efficiency can meet the optimum required conditions of the combined performance of conventional helicopters and propeller aircrafts.
The numerical solutions of the investigation indicate that the modifications on the Z-9 lead to the following outcomes: max take off weight raises 25% (from 4000kg to 5000kg); the hover ceiling raises 90% (from1050m to2000m) ; the cruise altitude raises 11% (4500m to 5000m; the cruise speed raises 23%(293km to 360km/h); the hover efficiency FW up to 0.6; the propulsion efficiency η up to 0.7.
Therefore, the best lift/thrust force ratio under different modes are obtained in the orthogonal range by computational fluid dynamics method.
The following items need to pay attention to:
1-in page 1 on line 13, the abbreviation term "Z9" should be written for what is stand for before the abbreviation term.
2-in page 1 on line 39, the abbreviation term "RPM" should be written for what is stand for before the abbreviation term. For instance rotation per minute (RPM).
In my opinion, the paper can be accepted for publication with a minor revision. The article has the merit of indicating that there is a wide spectrum of prospective VDDF applications in the fluid dynamics field, common vehicles like flying cars.
Author Response
Point 1: in page 1 on line 13, the abbreviation term "Z9" should be written for what is stand for before the abbreviation term.
Response 1: The “Z9” is not an abbreviation term but a code of a Chinese utility helicopter. The detailed description is added on line 14.(the line number is changed because of the revise of the previous manuscript)
Point 2: in page 1 on line 39, the abbreviation term "RPM" should be written for what is stand for before the abbreviation term. For instance rotation per minute (RPM).
Response 2: The abbreviation term “RPM” is written for rotation per minute(RPM) on line 41. (the line number is changed because of the revise of the previous manuscript)
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
Thanks for the update.
