Propeller advance is an important development in the field of electric aviation that can potentially pave the way for quiet and efficient electric aircraft. Electric aviation has been gaining momentum in recent years, as the aviation industry seeks to reduce its carbon footprint and move towards more sustainable modes of transportation. One of the main challenges of electric aviation is the limited range of electric aircraft, which is due to the limitations of current battery technology. However, propeller advance is a technology that can help to improve the efficiency of electric aircraft and extend their range.
Electrification is seen as having a significant role to play in the future of fossil-free aviation. However, electric aviation faces a trade-off problem: the more energy-efficient an electric aircraft is, the noisier it becomes. Researchers at Chalmers University of Technology in Sweden have developed a method for optimizing propeller design, paving the way for quiet, efficient electric aviation.
Electrification has been described as playing an important role in reducing emissions from future aviation in recent years. Due to the difficulties of longer ranges, interest is primarily focused on electric propeller planes that cover shorter distances. For regional and domestic flights, propellers connected to electric motors are considered the most efficient propulsion system.
But while airplanes are electric, propellers cause another kind of emission — noise. The noise from the propeller blades wouldn’t just disturb air passengers. Future electric aircraft will need to fly at relatively low altitudes, with noise disturbance reaching residential areas and animal life.
Modern aircraft propellers typically have two to four blades, but we discovered that by designing a propeller with six blades using our optimisation framework, you can create one that is both relatively efficient and quiet.
Hua-Dong Yao
Battling a trade-off dilemma
This is where the scientific community is at a crossroads. The goal of developing electric aircraft that are both quiet and efficient is hampered by a trade-off problem.
“We can see that the number of blades on a propeller reduces noise emissions. However, with fewer blades, propulsion becomes more efficient, and electric aircraft can fly for longer periods of time. There is a trade-off between energy efficiency and noise in this sense. This is a challenge for electric aircraft that are both quiet and efficient “explains Hua-Dong Yao, Associate Professor and researcher at the Chalmers University of Technology in fluid dynamics and marine technology.
An optimised design for quiet and efficient propellers
Hua-Dong Yao and his research colleagues, on the other hand, may be one step closer to a solution. They were successful in isolating and investigating the noise that occurs at the tip of the propeller blades, known as “tip vortices,” a well-known but little-studied source of noise. The researchers were able to fully understand the role of this noise in relation to other noise sources generated by propeller blades after isolating it.
The team discovered a way to optimize the propeller design and even out the trade-off effect between efficiency and noise by adjusting a variety of propeller parameters such as pitch angle, chord length, and a number of blades. The method, described in the study published in the journal Aerospace, can now be used in the design process of quieter propellers for future electric aircraft.
“Modern aircraft propellers typically have two to four blades, but we discovered that by designing a propeller with six blades using our optimization framework, you can create one that is both relatively efficient and quiet. When compared to a three-bladed propeller, the propeller achieves a noise reduction of up to 5-8 dBA* with only a 3.5% thrust penalty. That’s comparable to someone switching from speaking in a normal conversation voice to the sound you’d hear in a quiet room” Hua-Dong Yao concurs.
* A-weighted decibel (dBA or dB(A)) is a measure of the perceived loudness of sounds by the human ear. When compared to a flat audio decibel measurement, A-weighting gives more weight to frequencies in the mid-range of human hearing and less weight to frequencies at the edges. The A-weighting method is used to assess hearing damage and noise pollution.
