Development and progress in aeroacoustic noise reduction on turbofan aeroengines

Liu, Xiran; Zhao, Dan; Guan, Di; Becker, Sid; Sun, Dakun; Sun, Xiaofeng

doi:10.1016/j.paerosci.2021.100796

Cited by 40 publications

(9 citation statements)

References 54 publications

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“…In general, reducing the baffle length (normalized with the resonant neck diameter) from 2/3 to 1/3 leads to an improved TL max and increased resonant frequency. [70][71][72][73][74] This could be easily observed and compared from Figures 11(a) to (c).…”

Section: Effect Of the Length Of The Single Bafflementioning

confidence: 74%

Numerical optimizing noise damping performances of Helmholtz resonators with a rigid baffle implemented at neck in presence of a grazing flow

Guan

2022

Journal of Low Frequency Noise, Vibration and Active Control

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As an applicable noise attenuator, Helmholtz resonator is mainly used to dampen acoustic noise at low- and medium-frequency ranges. It is typically implemented in combustion-engines and gas turbines to dampen thermoacoustic instabilities. However, it has a narrow effective frequency range and does not work effectively at off-design conditions. In this work, we consider a modified structured Helmholtz resonator (HR) at its neck by applying a rigid baffle in order to maximize its’ noise damping effect and to broaden its frequency bands. The resonator is attached to a cylindrical duct/pipe in presence of a mean flow (grazing flow), aiming to simulate the practical engines flow configuration. For this, a two-dimensional frequency domain numerical model is developed by using COMSOL V5.3. The numerical simulations are carried out by solving the linearized Navier–Stokes equation in frequency domain with low computational cost and time. In order to obtain an optimum design in terms of the maximum noise damping performances, 10 new different configurations/designs are proposed. The effects of 1) the single baffle attached to the upstream or downstream sidewall of the neck ends, that is, Design A, B, C, and D or double baffles, that is, Design E, F, G, and H), 2) the baffle implementation location, 3) the length of the rigid baffle, and 4) the grazing flow low Mach number are evaluated and compared. It is found that Design C is associated with improved TL by 50% and decreased resonant frequency by 20% comparing with the conventional HR. The present preliminary study shows that Design C is the better design. Further experimental and optimization researches are needed to sheds light on the optimum design of a Helmholtz resonator with neck structure being modified, as there is a low Mach number grazing flow.

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Section: Effect Of the Length Of The Single Bafflementioning

confidence: 74%

Numerical optimizing noise damping performances of Helmholtz resonators with a rigid baffle implemented at neck in presence of a grazing flow

Guan

2022

Journal of Low Frequency Noise, Vibration and Active Control

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“…When reducing noise at the same time, a median filter works better than a convolutional one. In image processing, this nonlinear method is frequently employed to minimize "salt and pepper" noise [29] . When reducing noise at the same time, a median filter works better than a convolutional one, as shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

Diabetic retinopathy detection using Bilayered Neural Network classification model with resubstitution validation

Omer

2024

MethodsX

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“…[1][2][3][4] Such nonlinearity can bring great impacts on handling quality, ride quality, and structural fatigue life. [5][6][7][8] Free-play has been recognized as a non-negligible inducement of these problems, because it is the most significant source of structural nonlinearity. [9][10][11][12] Various methods have been developed to study nonlinear aeroelastic behaviors induced by free-play.…”

Section: Introductionmentioning

confidence: 99%

Aeroelastic investigation on an all-movable horizontal tail with free-play nonlinearity

Ai,

Bai,

Qian

et al. 2023

Journal of Low Frequency Noise, Vibration and Active Control

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Free-play-induced nonlinear dynamic behavior has been one of the most important topics of aeroelastic research in recent decades. In this paper, the describing function (DF) method is developed to investigate the complex dynamic response of a popular all-movable horizontal tail with free-play. Piecewise expressions for the time history and phase portrait of limit cycle oscillation (LCO) are derived by the developed DF method, which is conducive to understand the mechanism of free-play-induced LCO. Another advantage of the developed DF method is the ability to predict the high-order harmonics, which cannot be realized by the classic DF method. A three-dimensional (3D) all-movable horizontal tail model with torsional free-play was designed and manufactured to implement wind tunnel tests via various initial parameters. A good agreement was found between the numerical and experimental results, which can demonstrate the effectiveness of the proposed method. The influence of the initial parameters of the all-movable horizontal tail on the LCO characteristics is analyzed by both numerical calculations and wind tunnel tests. The method and results in this paper can provide a significant reference for the design of all-movable horizontal tail versus the free-play-induced LCO.

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Development and progress in aeroacoustic noise reduction on turbofan aeroengines

Cited by 40 publications

References 54 publications

Numerical optimizing noise damping performances of Helmholtz resonators with a rigid baffle implemented at neck in presence of a grazing flow

Numerical optimizing noise damping performances of Helmholtz resonators with a rigid baffle implemented at neck in presence of a grazing flow

Diabetic retinopathy detection using Bilayered Neural Network classification model with resubstitution validation

Aeroelastic investigation on an all-movable horizontal tail with free-play nonlinearity

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