scholarly journals Analysis of Composite Scrubber with Built-In Silencer for Marine Engines

2021 ◽  
Vol 9 (9) ◽  
pp. 962
Author(s):  
Myeong-rok Ryu ◽  
Kweonha Park
Keyword(s):  
Noise Reduction ◽  
Transmission Loss ◽  
Flow Characteristics ◽  
Low Frequency ◽  
Frequency Region ◽  
Reverse Direction ◽  
Sulfur Oxide ◽  
Noise Characteristics ◽  
Average Transmission ◽  
Reduction Effect

The International Maritime Organization (IMO) is strengthening regulations on reducing sulfur oxide emissions, and the demand for reducing exhaust noise affecting the environment of ships is also increasing. Various technologies have been developed to satisfy these needs. In this paper, a composite scrubber for ships that can simultaneously reduce sulfur oxide and noise was proposed, and the flow characteristics and noise characteristics were analyzed. For the silencer, vane type and resonate type were applied. In the case of the vane type, the effects of the direction, size, and location of the vane were analyzed, and in the case of the resonate type, the effects of the hole location and the number of holes were analyzed. The result shows that the length increase of the vane increased the average transmission loss and had a great effect, especially in the low frequency region. The transmission loss increased when the vane was installed outside, and the noise reduction effect was excellent when the vane was in the reverse direction. In the resonate type, increasing the number of holes is advantageous for noise reduction. The condition for maximally reducing noise in the range not exceeding 840 Pa, which is 70% of the allowable back pressure, is a vane length of 225 mm in the outer vane reverse type. The pressure drop under this condition was 777 Pa, and the average transmission losses in the low frequency region and the entire frequency region were 43.5 and 54.5 dB, respectively.

scholarly journals Flow characteristics and noise reduction effects of air cleaners of automobile intake systems with built-in resonators with space efficiency

2021 ◽  
Vol 9 (3A) ◽  
Author(s):  
Hoseop Song ◽  
◽  
Haengmuk Cho ◽  
Keyword(s):  
Pressure Drop ◽  
Noise Reduction ◽  
Transmission Loss ◽  
Flow Analysis ◽  
Flow Characteristics ◽  
Helmholtz Resonator ◽  
Space Efficiency ◽  
Engine Room ◽  
Air Cleaner ◽  
Reduction Effect

In an automobile intake system, Helmholtz resonator is often used to reduce intake noise. But there is a disadvantage in the engine room. Resonator brings low engine room space efficiency, because resonator needs some. In this paper, we propose air cleaner with built-in resonator for a limited space of air cleaner and analyze the pressure drop effect and the transmission loss performance of the resonator through flow analysis. The air cleaner with a built-in resonator had almost no difference in pressure drop with the conventional air cleaner. Some vortex in conventional air cleaner is removed, and also, the built-in resonator has noise reduction effect at 160Hz at 61dB such as same resonator.

scholarly journals Improvement of noise reduction performance in bellows using multilayer perforated panels

2021 ◽  
Vol 13 (1) ◽  
pp. 168781402098625
Author(s):  
Hee-Min Noh
Keyword(s):  
Noise Reduction ◽  
Multilayer Structure ◽  
Transmission Loss ◽  
Low Frequency ◽  
Frequency Region ◽  
Design Parameters ◽  
Railway Vehicle ◽  
Noise Performance ◽  
Analysis Model ◽  
Railway Vehicles

When the speed of a railway vehicle increases, the level of noise inside the vehicle inevitably increases as well, which is a major cause of discomfort to passengers. The most effective method is to improve the overall noise reduction performance of a vehicle. In particular, the gangway of the railway vehicle is made of silicone rubber; therefore, its noise reduction performance is inferior to that of other components of the vehicle. Thus, it is essential to improve the interior noise performance of railway vehicles. This study aims to reduce the noise in the low-frequency region of a railway vehicle gangway. It examines the applicability of the multi-layered resonance type panel, which has not been previously applied to the bellows in railway vehicles. In particular, the transmission loss was improved by changing the structure without filling the bellows with sound-absorbing material. First, a theoretical review of the noise reduction performance of a perforated multilayer structure was performed. Based on this, the major design parameters of the perforated multilayer structure that are effective in reducing noise in the low-frequency region of the bellows were derived. Through this, it was confirmed that in the multilayered structure, the hole diameter of 1 mm was effective in increasing the transmission loss in the low-frequency region, and the transmission loss was improved at 1% of the porosity. In addition, through a simple two-dimensional analysis model, it was confirmed that the transmission loss of the porous panel was improved at low frequencies of 100 to 400 Hz. Based on this result, a gangway with perforated multilayer structures was developed and tested. Through this verification test, it was confirmed that the noise performance of 9.2 dB was an improvement in the low frequency range of 100 Hz.

Experimental Study on Basic Performance and Noise Characteristics of Rubber Cement Concrete with Silica Fume

2014 ◽  
Vol 543-547 ◽  
pp. 4027-4030 ◽  
Author(s):  
Wei Li ◽  
Zhen Huang ◽  
Xiao Chu Wang ◽  
Jian Peng Zhang
Keyword(s):  
Flexural Strength ◽  
Noise Reduction ◽  
Silica Fume ◽  
Rubber Particle ◽  
Performance Testing ◽  
Cement Concrete ◽  
Noise Characteristics ◽  
Tension And Compression ◽  
Rubber Cement ◽  
Reduction Effect

This article has carried on the silicon ash content under the condition of 10%, and different rubber particle size and different dosage of silica fume rubber modified cement concrete in all kinds of performance testing, such as: the experiment research on compressive strength, splitting tensile strength, flexural strength and strong noise reduction performance. Experimental results show that silica fume can help improve the compression, splitting and flexural strength of rubber concrete, ratio of fracture and pressure and ratio of tension and compression of concrete are improved greatly after adding silica fume;With the increase of rubber particles, dynamic modulus of concrete decreased, noise reduction effect of silica fume concrete is significantly modified .

Aeroacoustic Characteristics of Cavity and Effect Study of Mesh on Noise Suppression

2013 ◽  
Vol 421 ◽  
pp. 104-109
Author(s):  
Jing Sun ◽  
Guang Jun Yang ◽  
Jian Jun Liu
Keyword(s):  
Noise Reduction ◽  
Noise Suppression ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Cavity Flow ◽  
Noise Spectrum ◽  
Effect Study ◽  
Suppression Effect ◽  
Reduction Effect ◽  
Suppression Effects

To explore the noise suppression effect of mesh on cavity, the wind tunnel experiment is carried out based on the analysis of clean cavity flow characteristics. The meshes are arranged both in the cavity and at the leading edge of the cavity. Through the analysis of pressure distribution on the cavity bottom and the noise spectrum monitored at front and rear walls respectively, noise suppression effects of mesh programs relative to the clean cavity and changes in the flow field are studied, the results show that the mesh inside the cavity has a better noise reduction effect. The work in this paper provides an effective way for cavity noise reduction.

scholarly journals Study on flow noise characteristics of Bionic cylinder based on acoustic analogy

2021 ◽  
Vol 336 ◽  
pp. 01003
Author(s):  
Zixian Cui ◽  
Hao Song ◽  
Qi Li ◽  
Buchao An ◽  
Lin Su
Keyword(s):  
Noise Reduction ◽  
Reynolds Numbers ◽  
Wake Flow ◽  
Cylinder Surface ◽  
Acoustic Analogy ◽  
Fluctuating Pressure ◽  
Flow Noise ◽  
Noise Characteristics ◽  
Reduction Effect ◽  
Serrated Structure

The drag and noise reduction of the flow around a cylinder is one of the important topics in hydrodynamics and acoustics. In this paper, three typical bionic cylinders are designed based on the serrated structure on the surface of shark skin. Using Large eddy turbulence model and Lighthill’s acoustic analogy method, the flow noise characteristics of smooth cylinder and three kinds of bionic cylinders at different Reynolds numbers were compared, and the structure of cylinder surface was optimized. The results show that the main source of the flow noise around a cylinder is dipole noise, which is caused by the periodic fluctuating pressure on the cylinder surface.The bionic cylinder can reduce the amplitude of the fluctuating pressure, improve the wake flow field and reduce the wake vorticity, so as to reduce the noise. Among the three kinds of bionic cylinder, V-shaped bionic cylinder has the best noise reduction effect, and the critical value of S/H of V-shaped cylinder is about 2.5. When s / h > 2.5, V-shaped bionic cylinder has no effect of noise reduction.

Multi-objective optimization of muffler for vehicle air-conditioning compressor pipeline

2021 ◽  
Author(s):  
Ming Li ◽  
Gaolin Hou ◽  
Lei Shu ◽  
Changhua Wei ◽  
Yan Jiang
Keyword(s):  
Noise Reduction ◽  
Air Conditioning ◽  
Transmission Loss ◽  
Structural Parameters ◽  
Original Structure ◽  
Air Conditioning System ◽  
Average Transmission ◽  
Final Optimization ◽  
Air Conditioning Systems ◽  
Orthogonal Optimization

The noise reduction of air-conditioning systems has gradually become an urgent problem with the comfortable requirement of driving, and the muffler is a commonly used noise reduction equipment for air-conditioning pipeline. In this article, the transmission loss of prototype muffler is co-simulated at different speeds. For optimizing the muffler, a new method that combines orthogonal optimization and detailed optimization is proposed. In orthogonal optimization, the multi-objectives orthogonal test is used to analyze the effect of four structural parameters (the shoulder height, the length of the cavity, the diameter of cavity, and the length of intubation) on the average transmission loss, the transmission loss at 1120Hz, and the frequency band width below 4dB. The influence of different factors on the transmission loss is studied at different speeds, and it found that the length of intubation has a significant impact on the transmission loss. In detailed optimization, the method is characterized by rapidity in the design of air conditioning system of vehicle, and the final optimization model is determined. The results show that the optimized structure is better than the original structure. The maximum reduction of average noise can reach 11.99dB, and the maximum noise reduction at 1120Hz reach 8.58dB.

Study on Performance of Automobiles Muffler Based on Sound Transfer Matrix Theory

2012 ◽  
Vol 197 ◽  
pp. 134-138 ◽  
Author(s):  
Qi Guo Hu
Keyword(s):  
Transfer Matrix ◽  
Matrix Theory ◽  
Transmission Loss ◽  
Low Frequency ◽  
Expansion Chamber ◽  
Fluid Analysis ◽  
Average Transmission ◽  
Tube Expansion ◽  
Insertion Tube ◽  
Single Insertion

According to the characteristics of automobiles exhaust noise of high pressure level and middle-low frequency, combining sound transfer matrix theory and FEM-Fluid analysis method, simulations of the transmission loss with non-insertion tube expansion chamber muffler, single insertion tube expansion chamber muffler and dual insertion tube expansion chamber muffler are carried out, which obtain the transmission loss curves of mufflers in different structures and different perforation rates. The results show that the max transmission loss and the average transmission loss of the muffler with perforation rate of 5% are greater than that of 3% and 10% below the low frequency of 200Hz; dual insertion tube expansion chamber muffler not only can increase the transmission loss below the frequency of 4000Hz, but also can effectively improve the performance of the mufflers in which have non-perforation tube and single insertion tube at some frequency points. The results of research can provide technical reference for exhaust muffler design of automotive.

scholarly journals Effect of Cavity Structure on Acoustic Characteristics of Phononic Crystals Based on Double-Layer Plates

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 995
Author(s):  
Chuanmin Chen ◽  
Zhaofeng Guo ◽  
Songtao Liu ◽  
Hongda Feng ◽  
Chuanxi Qiao
Keyword(s):  
Noise Reduction ◽  
Band Gap ◽  
Double Layer ◽  
Transmission Loss ◽  
Low Frequency ◽  
Phononic Crystals ◽  
Frequency Noise ◽  
Structural Factors ◽  
Low Frequency Noise ◽  
Cavity Structure

Localized resonance phononic crystals (LRPCs) are increasingly attracting scientists’ attention in the field of low-frequency noise reduction because of the excellent subwavelength band gap characteristics in the low-frequency band. However, the LRPCs have always had the disadvantage that the noise reduction band is too narrow. In this paper, in order to solve this problem, LRPCs based on double-layer plates with cavity structures are designed. First, the energy bands of phononic crystals plate with different thicknesses were calculated by the finite element method (FEM). At the same time, the mechanism of band gap generation was analyzed in combination with the modalities. Additionally, the influence of structure on the sound transmission loss (STL) of the phononic crystals plate and the phononic crystals cavity plates were analyzed, which indicates that the phononic crystals cavity plates have notable characteristics and advantages. Moreover, this study reveals a unique ”cavity cave” pattern in the STL diagram for the phononic crystals cavity plates, and it was analyzed. Finally, the influence of structural factors on the band structure and STL of phononic crystals cavity plates are summarized, and the theoretical basis and method guidance for the study of phononic crystals cavity plates are provided. New ideas are also provided for the future design and research of phononic crystals plate along with potential applications in low-frequency noise reduction.

Low Frequency Acoustic Performance in Ducts Using Honeycomb Layer Systems

2008 ◽  
Vol 15 (1) ◽  
pp. 21-34
Author(s):  
Wing-Cheong Tang
Keyword(s):  
Noise Reduction ◽  
Transmission Loss ◽  
Minimum Weight ◽  
Low Frequency ◽  
Superior Performance ◽  
Composite Sandwich ◽  
System A ◽  
Composite Sandwich Structures ◽  
Mass Spring ◽  
Air Cavities

The use of composite materials, like honeycomb structures, in the building industry is growing rapidly, due to their superior performance (very high Sound Transmission Loss) and significant weight reduction over conventional materials. An experimental investigation into low-frequency duct noise reduction using honeycomb sandwich panels is presented. Composite sandwich structures with an air gap between panels provide low-frequency sound absorption. The waves in the duct are coupled with those in the porous layer and the air cavities. The energy is dissipated as a result of the resonant mass-spring behavior of the system. A significant impact on the noise reduction is obtained by using a comparatively stiff honeycomb panel, in combination with a thin metallic duct wall with minimum weight. A noise reduction up to 12dB, below 300 Hz, is demonstrated.

scholarly journals Improvement of transmission loss of bellows through thickness improvement and structural modification

2021 ◽  
Vol 13 (9) ◽  
pp. 168781402110496
Author(s):  
Hee-Min Noh
Keyword(s):  
Simple Model ◽  
Transmission Loss ◽  
Layer Structure ◽  
Low Frequency ◽  
Frequency Region ◽  
Test Results ◽  
Noise Performance ◽  
Actual Performance ◽  
Low Transmission ◽  
Vibration Model

The bellows of the vehicle are vulnerable to noise because of the low transmission loss among the components. Therefore, in this study, we modified the thickness and the structure of the bellows to improve transmission loss. Based on the impedance tube test, the transmission loss of the silicon rubber specimen – the main material of the bellows – was analyzed; the results confirmed low transmission loss in the low-frequency region. An analysis of the natural vibration model of the simple model indicated that in the low-frequency region of the bellows, a number of vibrations occurred because of the vibration of the outer and inner components. Accordingly, to improve transmission loss, the improvement introduced by varying the thickness was analyzed, and the results confirmed that the noise performance improved by more than 3 dB for a thickness of 3.5 mm in the double-layer structure. In addition, the transmission loss improved in the low-frequency region after acoustic-structure coupling analysis was performed based on a simple model. To compare the actual performance between the existing and improved bellows, a noise comparison test was performed. The test results confirm that the existing noise reduction index improved by 3 dB from 30 to 33 dB when the thickness was increased to 3.5 mm; in the frequency domain, the highest noise performance was improved with an improvement of 5.6 dB at 160 Hz.

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