University of Illinois Urbana-Champaign

Performance mechanisms and integration of high-lift distributed propulsion systems

Jois, Himavath S.

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JOIS-DISSERTATION-2024.pdf

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https://hdl.handle.net/2142/127222

Description

Title
Performance mechanisms and integration of high-lift distributed propulsion systems
Author(s)
Jois, Himavath S.
Issue Date
2024-11-27
Director of Research (if dissertation) or Advisor (if thesis)
Ansell, Phillip J
Doctoral Committee Chair(s)
Ansell, Phillip J
Committee Member(s)
  • Merret, Jason M
  • Saxton-Fox, Theresa A
  • Chamorro Chavez, Leonardo P
Department of Study
Aerospace Engineering
Discipline
Aerospace Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
  • distributed propulsion
  • high-lift aerodynamics
  • supercirculation
  • thrust-vectoring
  • numerical modeling
Abstract
Recent interest into distributed electric propulsion in aeronautics has motivated the exploration of novel approaches for fixed-wing aircraft integration. Distributed propulsion can increase the overall lift generated by an aircraft high-lift system through the mechanisms of thrust-vectoring and supercirculatory coupling. The present work aims to build a more comprehensive understanding of the aerodynamic performance of distributed-propulsion-based high-lift systems. Both computational and experimental methods are leveraged in this research. A computational scheme based on the assumptions of two-dimensional potential flows was developed for aeropropulsive applications as an extension of previous modeling approaches. A panel method utilizing linearly varying vortex strengths was applied for discretized airfoil and propulsive wake geometries. The scheme iteratively solves for the circulation distribution on the airfoil elements and the shape of the propulsive wake, taking the system angle-of-attack and thrust coefficient as inputs. The system lift coefficient, airfoil surface pressure distributions, and off-body velocity distributions could be calculated from these results. Verification of the modeling scheme calculations and validation of solution accuracy with experimental data were performed. To that end, a set of wind tunnel experiments were configured using a quasi-2D distributed electric propulsion model developed for high-lift using the numerical scheme. The model incorporated ten electric ducted fans in an over-wing configuration, complete with axisymmetric-to-rectangular flow conditioning bodies to transition the cross-section of the flow in the propulsive nozzle to a rectangular exit. Two plain hinged flaps were incorporated at the nozzle exit to facilitate thrust vectoring. Surface pressure distributions, aggregate loads, and individual ducted fan thrust were all measured. In addition, a stereoscopic particle-image velocimetry campaign was conducted to measure the off-body flow velocity and vorticity in the wake of the model. Finally, tufts flow visualization was performed to examine three-dimensional flow characteristics. Results from the experimental campaign revealed several key flow phenomena and design challenges important for distributed propulsion high-lift systems. The lift coefficient of the system was found to increase for increasing thrust-vectoring flap deflection and increasing fan thrust, reinforcing the supercirculatory coupling between the propulsive wake and aerodynamic surfaces. Comparing experimental pressure and wake circulation distributions to computational predictions validated the accuracy of the scheme for inviscid-dominated flows. Thrust-drag bookkeeping methods revealed that both the system drag and pitching moment coefficients were highly sensitive to fan thrust and vectoring. In sum, the results from this research reinforce the relationships between several flow mechanisms important to the performance of aeropropulsive high-lift systems.
Graduation Semester
2024-12
Type of Resource
Thesis
Handle URL
https://hdl.handle.net/2142/127222
Copyright and License Information
Copyright 2024 Himavath S. Jois. All rights reserved.

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