Aerodynamic survey of lift-plus-cruise evtol geometries and respective drag reduction elements using reynolds average navier-stokes

Zheng, Wanzheng

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https://hdl.handle.net/2142/120142 Copy

Description

Title

Aerodynamic survey of lift-plus-cruise evtol geometries and respective drag reduction elements using reynolds average navier-stokes

Author(s)

Zheng, Wanzheng

Issue Date

2023-05-02

Director of Research (if dissertation) or Advisor (if thesis)

Merret, Jason M

Department of Study

Aerospace Engineering

Discipline

Aerospace Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Computational Fluid Dynamics
• eVTOL
• Drag Reduction
• Applied Fluid Dynamics

Abstract

With the emerging interest in sustainable aviation and urban air mobility achieved by electric vertical takeoff and landing aircraft, it is natural to question which type of design would be most suitable. To provide a quantitative answer from an aerodynamic perspective to this discussion, simulations are performed on two configurations developed from Smart Transportation Infrastructure Initiative (STII) conceptual design of a lift-plus-cruise eVTOL: One with open rotors installed on a rod under the wing and one with shrouded rotors installed in the wing. Simulations were also performed to investigate the sensitivity of aerodynamic coefficients to other potential design variables. It was found that although open rotors installed on an under-wing pylon were superior to shrouded rotors installed in a canoe if no drag reduction elements are implemented. The canoe configuration would provide more potential for improvements: using a rotor door to cover the first rotor opening would reduce the drag experienced by the canoe configuration below that seen on the rod configuration. Average drag reduction with covering the first rotor and all rotors was 66 and 165 counts, respectively. Changing rotor distributions along the chordwise direction had minimal impact on drag reduction, and placing rotors along the spanwise direction was not advised due to the increase of the projected frontal area. Increasing canoe chord length did not have significant impact on drag reduction if rotor doors were not implemented. If rotor doors were implemented, increasing canoe size had negative impact on drag. Rounding rotor edges did not change the aerodynamic performance of the canoe case but promotes vertical air intake when running lifting fans. Drag received by the canoe configuration correlated to rotor diameter in a parabolic manner, with 126 counts of drag if the rotor diameter was 0 and 377 counts if the rotor diameter was 2.95 ft. Fuselage and tail added an average 179 counts of drag, and thus the aforementioned differences were still significant in the scale of aerodynamic properties of the full configuration. This study also discussed the concept of using flow directing mechanisms such as a semicircular obstacle instead of rotor doors to reduce drag for the canoe configuration. A step added to the pressure surface before the rotor opening will divert flow and prevents flow recirculation into the rotor duct, thus achieving drag reduction with lower integration complexity and weight penalties compared to rotor doors. Adding a step in front of the first rotor at pressure surface and covering the first duct opening at suction surface results in identical aerodynamic performances with respect to adding rotor doors to both openings of the first duct. Applying the same drag reduction technique to the first and second rotor ducts from the leading edge results in, on average, 76.2% of the performance ceiling of this configuration, compared to 48.7% of the performance ceiling with no drag reduction elements applied. Increasing height of the step will result in turbulent flow downstream thus increasing drag introduced by flow stagnation at the step. The drag reduction is shown to be three dimensional effects as similar drag reduction was not observed on two dimensional simulations over the same geometry and circular step coupled with circular cavity shows higher efficiency on drag reduction over straight step coupled with rectangular duct.

Graduation Semester

2023-05

Type of Resource

Thesis

Copyright and License Information

Copyright 2023 Wanzheng Zheng

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