Design And Analysis Of Serrated Leading Edge Of Low Noise Uav Propellers

Multi-copters are currently widely applied in many applications,such as mapping,aerial photography,rescue operations,logistics and so on.However,the aerodynamic noise of UAV is one of the key factors restricting its civil application,so reducing the noise of propellers can help UAV manufacturers design more competitive products.Inspired by the silent flight of the owls and the research of the serrated leading edge in the two-dimensional airfoils,the serrations were applied on the propeller of a commercial quadcopter.By choosing different parameters of serrations,i.e.the height and wavelength,the aerodynamic and noise tests of these propellers at different rotational speeds were conducted.The parameter is chosen in such a way so as to explore the aerodynamic and aeroacoustic performance of isolated multi-copter propellers at the forward flight condition,and to search the law of sound pressure lever reduction(?SPL)and the best designed propeller of the serration parameters.The serrations reduce the thrust during the forward flight of the propeller,and increase the torque and power consumption,thereby reduce the overall aerodynamic performance.The thrust of the propeller increases and then decreases while increasing the height of the serration.However,the thrust decreases monotonically while increasing the wavelength.The torque and power consumption increase while increasing height of the serration,and decrease while increasing the wavelength.The analysis of data from the serrated propellers with the same aspect ratio shows that the two propellers are similar in aerodynamic performance.In terms of aeroacoustic performance,the leading edge serrations significantly reduce the mid and high frequency broadband noise during the forward flight,and the mid and high frequency broadband noise reduction is more sensitive to the wavelength than the height.The smaller the wavelength of serration is,the larger the broadband noise reduction will be.The tonal noise mainly depends on the aerodynamic performance of different serrated propellers.In addition,the sound pressure level reduction of the serrated propeller has a significant linear logarithmic law with the frequency before reaching the maximum.From the application perspective of UAV and propeller manufacturers,the noise emission is compared when the two propellers generate the same thrust.Therefore,although the leading edge serrations reduce the aerodynamic performance of the propeller,they improve propeller's acoustic performance.When generating equal thrust,the leading edge serrations reduce the noise emission,and the propeller with the highest serrations has the largest noise reduction.The aerodynamic-aeroacoustic performance of serrated propellers with the same aspect ratio is also similar.Therefore,the aspect ratio may be a more critical factor determining the aerodynamic-aeroacoustic performance of the propeller,which is recommended for future study.