Investigation of noise reduction effects of individual and combined geometrical modifications on UAM propeller blades

Abstract

The development of a future transportation concept in cities may also include transportation of passenger and cargo at various altitudes in order to reduce the load on the ground infrastructure. This is known as urban air mobility (UAM), facilitated by the application of electrical vertical take-off and landing (eVTOL) vehicles. Public acceptance is required with regard to safety aspects in densely populated areas, but also in terms of noise emissions. As with almost any aircraft, the propulsion systems, in most cases the propeller blades, are the main source of noise generation. In literature, experimental and numerical results for geometric blade modifications for the purpose of noise reduction are provided only for small diameter propellers. This paper investigates the individual features at larger diameter propellers by means of numeric aeroacoustic simulations with OpenFOAM. The modifications include serrations of the trailing edge, leading edge tubercles and blade tip adaptations. Moreover, the combination of those features is investigated in a parameter study for various rotational velocities and several flight modes. The key effect, namely a reduction of broadband noise, can be observed for several cases, but the strength of it varies. An optimization process is necessary to obtain an efficient noise reduction for all operating conditions of a particular aircraft design.