School of Mechanical Engineering Seminar
Monday 23.10.2023 at 14:00

ZOOM SEMINAR

INTEGRATED DISTRIBUTED PROPULSION ON AN AERODYNAMIC

PROFILE

Ofek Katz

M.Sc. student of Prof. Avi Seifert

School of Mechanical Engineering, Tel Aviv University, Tel Aviv, Israel

With the progress of electrical battery technology and the commitment to minimizing the environmental footprint of aeroplanes, fresh prospects for creative aerodynamic solutions have emerged. Embracing electric motors paves the way for a comprehensive aircraft reconsideration, enabling the distributed propulsion system's fusion into the airframe. This endeavour aims to enhance aerodynamic efficiency, marking a paradigm shift. This research was undertaken to explore the enhancements brought about by integrated distributed propulsion into the wing.

Distributed propulsion has a wide range of implementations. In this study, the concept examined is small (relative to the wing chord of 8%) motors integrated within the airframe to the upper curve of the airfoil. The wing's geometry is based on MH-93 airfoil with electric motors. The air suction from the motor inlet creates a low pressure near the trailing edge, thus accelerating flow from upstream and creating lower pressure across the chord. At the same time, the high-velocity flow from the motor’s exit fills the energy deficit at the wake.   

A two-dimensional and three-dimensional numerical study was conducted concurrently to support the experimental efforts. The two-dimensional ANSYS CFD simulation was used as a starting point for the study as a fast and reliable result, using the k-ω SST RANS model. The results show significant benefits of increased maximum lift while reducing the drag at Reynolds numbers of order one million. The three-dimensional simulation was performed for a more detailed calculation and to tailor the CFD predictions to the experimental test model and its interaction with the wind tunnel structure. The control volume, and the airfoil replicated more accurately the real lift model and the setup in the wind tunnels of the TAU Meadow aerodynamics laboratory. The data from the three-dimensional simulation show a similar trajectory of the results but a lower lift at the baseline.

The experimental investigation took place within two distinct wind tunnels. The measurements in the Knapp-Meadow wind tunnel were automated and pressure-based, incorporating a wake rake to ensure precise drag measurement. Meanwhile, direct force measurements were performed at the Low-Speed Low-Turbulence wind tunnel. A 3D-printed PLA model featuring fourteen incorporated electric motors was designed and manufactured for wind tunnel studies. The assessments encompassed a range of Reynolds numbers, angles of attack, and varying operational conditions of the motors.

The outcomes from both computational simulations and experimental studies reveal an enhancement in lift and a concurrent decrease in drag as motor-generated thrust intensifies. Additionally, the findings underscore that the gains in lift outweigh the expended energy, underscoring the role of active flow control technology rather than brute force. Compared to the conventional under-wing turbofan engine, distributed propulsion is an aircraft thrust producer, and an aerodynamic-enhancement tool. This combination showcases the potential for heightened efficiency of the system.