A descriptive assessment of electric aircraft propulsion noise

Abstract

One of the key technologies that can help achieving the climate targets set forth by the ICAO is the electrification of aircraft. Various scenarios about the future of aviation are beginning to include this emerging topic. The EU project PULSAR for instance is developing a roadmap for noise and emissions that takes technology improvements into account in order to attain net-zero emissions by 2050. The electrification of aviation will undoubtedly have a place in the different storylines that are being put together for this project. Despite the various obstacles that must be overcome, significant progress is being made in the development of electric aircraft. Many companies and research organizations are engaged in the development of electric aircraft, and some of them already have operational prototypes. Since public awareness is a major factor in changing the aviation industry, reducing noise can further ensure the industry's profitable growth. Early consideration of low-noise aircraft and propulsion system designs could give companies a competitive advantage. Therefore, noise needs to be considered early on in the development of electric aircraft. An overview of the electric propulsion systems being developed for short-, mid-, and long-range electric aircraft will be provided in this presentation. By showing several examples of the aircraft that companies and research institutions have developed and that are planned over the next few decades, the aviation industry's response to these technologies is evaluated. A qualitative assessment of various noise sources from electric propulsion systems is then provided. The modeling of noise sources from turbofan, turboprop, and propeller engines is something that research teams at the German Aerospace Center (DLR) have a great deal of experience with. The development of low-noise engines, such as those with improved fan and liner technologies, is made possible by this established understanding. Turbine, jet, and combustion noise will all be eliminated by electrifying turbofan and turboprop engines. However, additional electrical noise sources are added that are currently not accounted for in the preliminary design of electric propulsion systems. This gap has recently been filled by a DLR research group at the Institute of Electrified Aero Engines that focuses on modeling the noise sources of the components found in electric propulsion systems. This presentation will provide information about electric machines feasible for the aviation industry and the origins of their noise. In addition, numerical and analytical models established and being implemented by the DLR research group to provide a quantitative assessment of the noise sources of potential electric propulsion systems are introduced. Also, the currently under-construction acoustic experimental test rig designed by the aforementioned DLR research group is presented. It will allow the numerical and analytical models to be validated. These models will serve as a basis for an accurate noise assessment throughout the design phase of highly efficient electric machines producing the specific power needed to power electric aircraft. By merging these models with the ones now in use within the DLR, it will soon be feasible to perform a full quantitative assessment of the noise generated by electric aircraft.