Effects of number of blades on propeller noise

Baskaran, Kabilan; Jamaluddin, Nur Syafiqah; Celik, Alper; Rezgui, Djamel; Azarpeyvand, Mahdi

doi:10.1016/j.jsv.2023.118176

Cited by 14 publications

(1 citation statement)

References 25 publications

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“…This fundamental difference in behaviour in radiation between tones and broadband noise discussed above has been observed experimentally by Gojon et al 23 on a small low-speed propeller rig of APC 9x6 SF, APC 11x4.7 SF, and ISAE two at higher tip speeds. More recently, Baskaran et al 38 also have observed a similar trend in tonal and broadband noise with a change in blade numbers. The broadband noise was observed to be maximum at angles away from the plane of rotation and a minimum near the plane of rotation.…”

Section: Overall Sound Pressure Level (Oaspl) Directivitiesmentioning

confidence: 58%

On the balance between the tonal and broadband noise of isolated propellers

Akiwate,

Joseph,

Parry

et al. 2024

International Journal of Aeroacoustics

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This study presents a predominantly numerical and theoretical investigation into the balance of tonal and broadband noise due to an isolated propeller in uniform motion. The predicted trends in the balance between tonal and broadband noise radiation with varying blade number and speed of rotation is supported by preliminary experimental measurements. Here, we assume that the dominant noise generation mechanisms are the tones due to steady loading and blade thickness, while the broadband noise is due to boundary layer scattering at the trailing edge. The study also provides a detailed comparison between the tonal and broadband formulations to highlight their similarities and differences. In this paper, we show that the main differences in the behaviour and character of the tonal and broadband spectra and directivities are due to the number of acoustic modes that can be excited. This paper presents a parametric study in which the variation in tonal and broadband noise is investigated as a function of blade tip Mach number ( M t) and blade number ( B) whilst maintaining constant solidity and thrust. This study is repeated for three NACA airfoil profiles. It is found that tonal noise dominates at low blade number and low frequency and/or higher tip speeds, while broadband noise is the major contributor at high-frequencies and at high blade number and low tip speeds. The results show a clear distinction between the combinations of M t and B that are dominated by tonal and by broadband noise. These results are interpreted from fundamental principles relating to modal radiation efficiencies. We confirm this trend of balance between tonal and broadband noise with measured noise at different B and M t. The results of this paper will serve as useful guidelines for preliminary propeller design.

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Section: Overall Sound Pressure Level (Oaspl) Directivitiesmentioning

confidence: 58%

On the balance between the tonal and broadband noise of isolated propellers

Akiwate,

Joseph,

Parry

et al. 2024

International Journal of Aeroacoustics

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Effect of blade number on rotor efficiency and noise emission at hovering condition

Li,

Yang,

et al. 2024

Physics of Fluids

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The configuration of rotors significantly impacts the aerodynamic efficiency and noise emission of multicopters. To date, there are no general guidelines regarding how many blades a rotor should use for optimal aerodynamic performance and minimum noise emission. From the perspectives of aerodynamics and acoustics during the hovering condition, two key parameters, i.e., figure of merit (FM) and overall sound pressure level (OASPL), are evaluated to determine the optimal blade number (BN). The number of blades chosen in this study is BN = 2–6, which is largely observed in commercial multicopters. A genetic algorithm was developed to optimize blade design for each BN-rotor configuration. The individuals are evaluated by steady computational fluid dynamics (CFD) simulations and acoustic analogy for optimizations, and the detailed analyses of optimal ones are further explored by unsteady CFD simulations. The planform of the baseline blade is maintained, and the radial distribution of twist angles is the parameter for optimization. While generating the same thrust, the value of FM keeps increasing as the number of blades increases from 2 to 4, after which the FM value reaches a plateau. The value of OASPL keeps decreasing as the number of blades increases. The reason for the FM and OASPL value trends vs blade number is explained with the numerical simulation results, and a general design rule is suggested at the end.

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Analysis of hydrodynamic performance and acoustic characteristics of loop propellers

Cao,

Xu,

et al. 2024

Physics of Fluids

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To improve the efficiency and stealthiness of marine operations of autonomous underwater vehicles (AUVs), 12 loop propellers with different structural parameters are selected as research subjects. The Reynolds-averaged Navier–Stokes equations method is used to simulate the flow field result around the loop propellers and is combined with detached eddy simulation and the acoustic analogy method for hydrodynamic analysis and noise prediction. The influence of three structural parameters, namely the number of propeller blades, the thickness of propeller blades, and the pitch of propeller blades, on the hydrodynamic and noise performance of the propeller is investigated, and the loop propeller structure with the optimal hydrodynamic and noise performance is selected. The research results indicate that increasing the number of propeller blades and increasing the pitch of the loop propeller can significantly improve the thrust and torque of the propeller and effectively reduce the noise. However, increasing the thickness of the propeller blades can also increase the thrust and torque of the propeller, but it will sacrifice the noise performance of the loop propeller to a certain extent. The sensitivity of the noise performance with respect to the blade thickness is significantly higher than that of the two parameters of blade number and pitch. To verify the accuracy of the hydrodynamic and noise performance simulation results, this study conducted hydrodynamic and noise performance tests on the preferred loop propeller structure in the towing pool and anechoic pool and successfully verifies the reliability of the numerical simulation method used in this study for the prediction of the propeller performance by comparing the test data with the simulation results. This study provides theoretical support for the design optimization of loop propellers and helps to promote the design of high-efficiency and low-noise propellers in complex marine environments.

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Effects of number of blades on propeller noise

Cited by 14 publications

References 25 publications

On the balance between the tonal and broadband noise of isolated propellers

On the balance between the tonal and broadband noise of isolated propellers

Effect of blade number on rotor efficiency and noise emission at hovering condition

Analysis of hydrodynamic performance and acoustic characteristics of loop propellers

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