scholarly journals A parameter design method for multifrequency perfect sound-absorbing metasurface with critical coupled Helmholtz resonator

2021 ◽  
pp. 146134842110196
Author(s):  
Sun Wei ◽  
Li Li ◽  
Chu Zhigang ◽  
Li Linyong ◽  
Fan Xiaopeng
Keyword(s):  
Sound Absorption ◽  
Design Method ◽  
Structural Parameters ◽  
Low Frequency ◽  
Helmholtz Resonator ◽  
Programming Algorithm ◽  
Structural Parameter ◽  
Efficient Design ◽  
Harmonic Components ◽  
Frequency Harmonic

The low-frequency harmonic components of urban substation noise are easy to annoy the residents. Multi-frequency perfect sound-absorbing metasurface based on the Helmholtz resonator (HR) is an alternative solution to suppress the low-frequency harmonic noise. This paper proposes an efficient design method of structural parameter for the multi-frequency perfect sound-absorbing metasurface. Taking the perfect sound absorption at the target frequency as objective and the structural parameters of HR as optimization variables, the structural parameter optimization model of multi-frequency perfect sound-absorbing metasurface is established and solved by the sequential quadratic programming algorithm. The proposed design method effectively overcomes the deterioration of sound absorption performance caused by the combined design of multiple perfect sound absorption units. Utilizing the proposed method, we designed a multi-frequency perfect sound-absorbing metasurface to absorb the four harmonic components of an urban substation noise simultaneously. The finite element simulation results and the experimental results of the physical sample indicate that the designed multi-frequency perfect sound-absorbing metasurface can satisfy critical coupling to achieve perfect sound absorption at all target frequencies.

scholarly journals Research on structural parameter optimization and thermal performance of twin-screw expander

2019 ◽  
Vol 14 (3) ◽  
pp. 386-393
Author(s):  
Chenghu Zhang ◽  
Jiahao Gao ◽  
Jie Fu ◽  
Yaping Li ◽  
Jiyou Lin
Keyword(s):  
Thermal Performance ◽  
Torsion Angle ◽  
Structural Parameters ◽  
Programming Algorithm ◽  
Structural Parameter ◽  
Internal Expansion ◽  
Twin Screw ◽  
Expansion Angle ◽  
Sequence Method ◽  
Shaft Power

Abstract This paper analyzes rotor profile and meshing law of twin-screw expander. Elementary area is calculated by meshing sequence method, and elementary volume is solved by integration. The influence of geometric characteristics such as torsion angle and internal expansion angle of male rotor on the thermal performance of twin-screw expander is studied. The results show the following: reasonably reducing internal expansion angle and positive rotor torsion angle can increase isentropic adiabatic power of twin-screw expander. Taking isentropic adiabatic efficiency as optimization goal, sequential quadratic programming algorithm is used to optimize the structural parameters of twin-screw expander, and the influence of leakage on its functional force is analyzed. Considering leakage effect, actual shaft power of twin-screw expander is 16.7 kW, the isentropic adiabatic power under ideal conditions is 21.3 kW, and the adiabatic efficiency is 78.71%.

Theoretical and numerical study of nonlinear acoustic absorbers for low frequency noise control

2021 ◽  
Vol 263 (1) ◽  
pp. 5600-5604
Author(s):  
Min Yang ◽  
Xianhui Li ◽  
Zenong Cai ◽  
Junjuan Zhao ◽  
Peng Zhang ◽  
...  
Keyword(s):  
Sound Absorption ◽  
Averaging Method ◽  
Numerical Study ◽  
Structural Parameters ◽  
Low Frequency ◽  
Frequency Noise ◽  
Flow Equations ◽  
State Response ◽  
Runge Kutta Method ◽  
Absorption Performance

In this paper, the sound absorption characteristics of cubic nonlinear sound-absorbing structures are analyzed by theoretical and numerical methods. The slow flow equations of the system are derived by using complexification averaging method, and the nonlinear equations which describe the steady- state response are obtained. The resulting equations are verified by comparing the results which respectively obtained from complexification-averaging method and Runge-Kutta method. It is helpful to optimize the structural parameters and further improve the sound absorption performance to study the variation of the sound absorption performance of cubic nonlinear structure with its structural parameters.

Broadening perfect sound absorption by composite absorber filled with porous material at low frequency

2020 ◽  
pp. 107754632098021
Author(s):  
Baozhu Cheng ◽  
Nansha Gao ◽  
Yunke Huang ◽  
Hong Hou
Keyword(s):  
Porous Material ◽  
Sound Absorption ◽  
Low Frequency ◽  
Material Structure ◽  
Frequency Noise ◽  
Complex Frequency ◽  
Acoustic Model ◽  
Efficient Design ◽  
Absorption Frequency ◽  
Plane Method

To enhance the low-frequency broadband sound absorption, we propose an absorber filled with porous material and establish a relative acoustic model. Based on the critical coupling condition, a Helmholtz absorber was designed to achieve perfect sound absorption at 172 Hz by the complex frequency plane method. Considering the weak adjustability and acoustic impedance of the Helmholtz absorber, we devised four absorber filled with porous material units that can achieve perfect sound absorption at discrete frequencies between 400 and 488 Hz with a thickness of only 51 mm. A composite absorber filled with porous material was designed by arranging four absorber filled with porous material units in a coplanar manner. The broadband perfect sound absorption of the composite absorber filled with porous material was subsequently verified by simulation and experiment. The thickness of the composite absorber filled with porous material is only 1/18 of the wavelength corresponding to the perfect absorption frequency, and it shows excellent subwavelength characteristics. The theoretical acoustic model of the composite absorber filled with porous material and the complex frequency plane method can achieve a more efficient design of broadband perfect sound absorbers. The composite absorber filled with porous material not only realizes low-frequency broadband perfect sound absorption but is also lightweight and easy to fabricate. This demonstrates the composite absorber filled with porous material structure has great potential for application in low to mid frequency noise control.

Comparison of multiple-layer versus multiple-cavity microperforated panels for sound absorption at low frequency

2021 ◽  
Vol 69 (4) ◽  
pp. 341-350
Author(s):  
Pedro Cobo ◽  
Francisco Simón ◽  
Carlos Colina
Keyword(s):  
Sound Absorption ◽  
Low Frequency ◽  
Single Layer ◽  
Helmholtz Resonator ◽  
Layer Versus ◽  
Low Frequencies ◽  
High Frequencies ◽  
Multiple Layer ◽  
Band Absorption ◽  
Microperforated Panels

Microperforated panels (MPPs) are recognized as suitable absorbers for noise control applications demanding special clean and health requirements.While it is relatively easy to design single-layer MPPs for sound absorption in one-to-two octave bands at medium-high frequencies, the performance for low frequencies (below 600 Hz) leads to a rather narrow-band absorption, similar to that of a Helmholtz resonator. However, multiple-layer MPPs can be designed as sound absorbers that yield low-frequency absorption in a wide frequency band. Recently, multiple-cavity perforated panels have been proposed to improve the performance of MPPs in the low-frequency range. In this article, the capability of multiple-layer and multiple-cavity MPPs to provide sound absorption at low frequencies is analyzed.

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