Low-Noise Propeller Design for Quiet Electric Aircraft

Inspired by the tremendous success of electric cars, the electrification technology has recently attracted a great deal of attention in aviation industry. This leads to the advent of massive efforts on the development of electric aircraft. Electrification enables zero CO2 and NOx emissions for aircraft in the near future. However, the annoying noise radiated from electrified propulsion systems is still a great challenge. The major noise sources are propellers. In particular, short-haul electric aircraft are usually flying from small airports near communities, which would exaggerate the noise impacts on residents. This paper presents a study on the propeller noise for a hypothetical electric aircraft. First of all, the acoustic study focuses on the effects of blade number, blade diameter, and rotation speed for an isolated propeller. Then, an unique configuration of dual-rotating propeller is briefly investigated to explore its potential of low-noise generation. Lastly, multiple propellers installed on an aircraft with various distributive propulsion strategies are investigated. The overall noise emission of these distributive propulsion strategies are promising to reduce the total noise from electric aircraft. Nonetheless, the noise level is very sensitive to the installation location of every propeller. An interesting finding is that the acoustic-wave interaction among the propellers are limited to the near field, and is insignificant in the far field. The present results are expected to enhance the understanding of propeller noise generation mechanisms, which are beneficial to propose guidelines on the development of low-noise distributive propulsion systems for electric aircraft