Tech Briefs Magazine - August 2023 - 26

Aeronautics
time, such as medical diagnosis and autonomous
driving applications, " Rus said.
The team's system was first trained on
data collected by a human pilot, to see how
they transferred learned navigation skills to
new environments under drastic changes
in scenery and conditions. Unlike traditional
neural networks that only learn
during the training phase, the liquid neural
net's parameters can change over time,
making them interpretable and more resilient
to unexpected or noisy data.
In a series of quadrotor closed-loop control
experiments, the drones underwent
myriad tests, and the team believes that the
ability to learn from limited expert data
and understand a given task while generalizing
to new environments could make autonomous
drone deployment more efficient,
cost-effective, and reliable.
For more information, contact Rachel
Makram Chahine, a PhD student in electrical engineering and computer science and an MIT CSAIL
affiliate, leads a drone used to test liquid neural networks. (Image: Mike Grimmett/MIT CSAIL)
Gordon at rachelg@csail.mit.edu; 617258-0675.
A
Quiet, Efficient Propeller Solution for Electric Aviation
Modern aircraft propellers usually have two to four blades, but the team used six to
maximize efficiency and minimize noise.
Chalmers University of Technology, Gothenburg, Sweden
E
lectrification is seen as having an important
role to play in the fossil-free aviation
of tomorrow. But the more energy-efficient
an electric aircraft is, the noisier its
propellers get. Now, researchers at Chalmers
University of Technology have developed
a propeller design optimization
method that paves the way for quiet, efficient
electric aviation.
" We can see that the more blades a propeller
has, the lower the noise emissions.
But with fewer blades, propulsion becomes
more efficient and the electric aircraft can
fly for longer. In that sense, there is a tradeoff
between energy efficiency and noise.
This is something of an obstacle for electric
aircrafts that are both quiet and efficient, "
said Associate Professor Hua-Dong Yao.
Now, the researchers may be one step
closer to a solution. They have succeeded
in isolating and exploring the noise that
occurs at the tip of the propeller blades -
" tip vortices " - a known but less-well-explored
source of noise. In isolating this
noise, the team was able to fully understand
its role in relation to other noise sources
generated by propeller blades.
By adjusting a range of propeller parameters
- e.g., pitch angle, chord length, and
number of blades - the team found a way
to optimize the propeller design and even
out the trade-off effect between efficiency
and noise. The method, published in the
journal Aerospace, can now be used in the
design process of quieter propellers for future
electric aircraft.
" Modern aircraft propellers usually have
two to four blades, but we've found that by
using six blades designed using our optimization
framework, you can develop a propeller
that's both relatively efficient and
quiet. The propeller achieves a noise reduction
of up to 5-8 dBA with only a 3.5 per
cent thrust penalty, compared to a propeller
with three blades. That's comparable to
the noise reduction of someone going
from speaking in a normal conversation
voice to the sound you would perceive in a
quiet room, " said Yao.
For more information, contact HuaResearchers
at Chalmers University of Technology have developed a propeller design optimization
method that paves the way for quiet and efficient electric aviation. (Image: www.chalmers.se)
26
www.techbriefs.com
Dong Yao at huadong.yao@chalmers.se;
+46 31-772-1405.
Tech Briefs, August 2023

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Tech Briefs Magazine - August 2023

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