Wyniki wyszukiwania - BazTech

1

Analysis of the combustion engine exhaust system structure in aspect of shaping acoustic energy

Gągorowski Andrzej

Combustion Engines

|

2023

|

R. 62, nr 2

112--116

EN

The flow of exhaust gases is the source of many physical processes, including thermal, acoustic, mechanical and chemical phenomena with high dynamics of changes. The study analyzes the impact of the entire structure of the exhaust system on the formation of acoustic energy, determining the transmission loss characteristics of its individual components and the entire system. On the example of a structure based on a proprietary solution of an adjustable reactive muffler, the possibilities of shaping the flow of acoustic waves in the process of designing and selecting exhaust systems for internal combustion engines were determined. The study was carried out with the use of the CFD method and a specialized package for advanced simulations AVL AST.

2

Evaluation of the Effect of Uncertainties on the Acoustic Behavior of a Porous Material Located in a Duct Element Using the Monte Carlo Method

Hannachi Hanen, Trabelsi Hassen, Kani Marwa, Taktak Mohamed, Chaabane Mabrouk, Haddar Mohamed

Archives of Acoustics

|

2023

|

Vol. 48, No. 1

81--91

EN

When studying porous materials, most acoustical and geometrical parameters can be affected by the presence of uncertainties, which can reduce the robustness of models and techniques using these parameters. Hence, there is a need to evaluate the effect of these uncertainties in the case of modeling acoustic problems. Among these evaluation methods, the Monte Carlo simulation is considered a benchmark for studying the propagation of uncertainties in theoretical models. In the present study, this method is applied to a theoretical model predicting the acoustic behavior of a porous material located in a duct element to evaluate the impact of each input error on the computation of the acoustic proprieties such as the reflection and transmission coefficients as well as the acoustic power attenuation and the transmission loss of the studied element. Two analyses are conducted; the first one leads to the evaluation of the impacts of error propagation of each acoustic parameter (resistivity, porosity, tortuosity, and viscous and thermal length) through the model using a Monte Carlo simulation. The second analysis presents the effect of propagating the uncertainties of all parameters together. After the simulation of the uncertainties, the 95% confidence intervals and the maximum and minimum errors of each parameter are computed. The obtained results showed that the resistivity and length of the porous material have a great influence on the acoustic outputs of the studied model (transmission and reflection coefficients, transmission loss, and acoustic power attenuation). At the same time, the other physical parameters have a small impact. In addition, the acoustic power attenuation is the acoustic quantity least impacted by the input uncertainties.

3

Transmission loss of absorptive mufflers lined with expanded clay granulates

Kosała Krzysztof

Vibrations in Physical Systems

|

2022

|

Vol. 33, nr 2

art. no. 2022216

EN

The article presents the results of tests on sound attenuation by two types of cylindrical absorptive mufflers with the same length and different diameters of chambers filled with expanded clay granulates. Using a laboratory stand for testing acoustic mufflers with an impedance tube, the transmission loss parameter was determined. To compare the effectiveness of sound attenuation, the transmission loss of mufflers without sound absorbing material was also determined. The results of these tests were compared to the results obtained with the use of a known calculation model for reflective mufflers. Using an impedance tube, the normal incidence sound absorption coefficients of the expanded clay granulates with thicknesses of material samples from 10 to 100 mm were determined. The dependence between the sample thickness and the first resonance frequency of the sound absorption coefficient was determined, which was then used in the proposed calculation model of the effectiveness of the cylindrical absorptive mufflers with expanded clay granulates. Using the proposed theoretical model, the results of transmission loss calculations, satisfactory for engineering applications, were obtained.

4

Analytical and Computational Acoustic Modelling of Side Outlet Muffler and Its Extension in the Modelling of Tapered Side Outlet Muffler

Vishwakarma Sandeep Kumar, Pawar Jayappa

Archives of Acoustics

|

2022

|

Vol. 47, No. 4

491--499

EN

Mufflers are popular in the suppression of noise levels coming from various machinery. The most common parameters for the evaluation of the performance of mufflers are transmission loss, noise level, and insertion loss. The transmission loss is evaluated for tapered side outlet muffler using finite element analysis without considering the fluid-structure interaction. This study includes analytical modelling and acoustic modelling of the side outlet muffler and transmission loss is in excellent agreement with the reference paper. The feasibility of the acoustic model is also verified with the experimental work on simple expansion chamber muffler. The same finite element analysis is extended for the tapered side outlet muffler. The transmission loss of the tapered side outlet muffler in the given frequency range is found 8.96 dB better than the side outlet muffler. The acoustic pressure level and sound pressure level contours for the tapered side outlet muffler give a clear picture of wave propagation inside the muffler. The effect of the cut-off frequency on the transmission loss of the tapered side outlet muffler can be seen from the contours. This study can be helpful in the determination of the performance of the mufflers in terms of transmission loss, the performance of mufflers above cut-off frequency, and design improvements in the muffler to avoid the higher-order modes of the sound wave.

5

Analysis of the Influencing Factors of the Acoustic Performance of the Muffler Considering Acoustic-structural Coupling

Zhao Bo, Li He

Archives of Acoustics

|

2022

|

Vol. 47, No. 4

479--490

EN

In the calculation of the acoustic performance of mufflers, the walls of mufflers are usually treated rigidly without considering the acoustic-structural coupling, but the results so calculated differ significantly from the actual situation. Based on the basic equations, the article derives the finite element equations of the muffler system while considering the acoustic-structural coupling effect and theoretically analyses the connection between the acoustic-structural coupling system and the structural and acoustic modes. The structural and acoustic modes of the muffler are calculated and the reasons for the mutation of the transmission loss curve of the muffler when the acoustic-structural coupling is considered are analysed. The results show that the acoustic-structural coupling is the result of the interaction between the structure and the air inside the expansion chamber under acoustic excitation, which manifests mutations in the sound pressure inside the muffler in some frequency bands. Then, using a single-chamber muffler as an example, the transmission loss is used to characterise the performance of the muffler. The effects of different factors such as shell thickness, structure, porous media material lining, and restraint method on the acoustic-structural coupling effect of the muffler are analysed, and the structure of a double-chamber muffler is successfully optimised according to the conclusions.

6

2D Modeling of Wave Propagation in Shallow Water by the Method of Characteristics

Khalilabadi Mohammad Reza

Archives of Acoustics

|

2022

|

Vol. 47, No. 3

407--412

EN

In this paper, a 2D numerical modeling of sound wave propagation in a shallow water medium that acts as a waveguide, are presented. This modeling is based on the method of characteristic which is not constrained by the Courant–Friedrichs–Lewy (CFL) condition. Using this method, the Euler time-dependent equations have been solved under adiabatic conditions inside of a shallow water waveguide which is consists of one homogeneous environment of water over a rigid bed. In this work, the stability and precision of the method of characteristics (MOC) technique for sound wave propagation in a waveguide were illustrated when it was applied with the semi-Lagrange method. The results show a significant advantage of the method of characteristics over the finite difference time domain (FDTD) method.

7

Stopband effect and sound transmission loss of periodic locally resonant structures

Juros Klara, Kras Aleksander, Kamisiński Tadeusz

Vibrations in Physical Systems

|

2021

|

Vol. 32, nr 1

art. no. 2021105

EN

This paper investigates the theoretical aspects of sound attenuation of periodic structures with locally resonant elements. The stopband effect in frequency characteristics of infinite periodic structures created by the resonant elements is investigated. The dispersion curves calculation procedure is described in details with the influence of resonance frequency and mass of added locally resonant structure on width of the obtained stopband is investigated. The theoretical formulation for calculation of the sound transmission loss for periodic structure is derived. The performance of the structure with locally resonant elements is evaluated based on dispersion curves obtained for an infinite periodic structure and transmission loss calculated for finite structure is conducted.

8

A novel merchant optimization algorithm for solving optimal reactive power problem

Lenin Kanagasabai

Journal of Automation Mobile Robotics and Intelligent Systems

|

2021

|

Vol. 15, No. 1

51--56

EN

In this paper Merchant Optimization Algorithm (MOA) is proposed to solve the optimal reactive power problem. Projected algorithm is modeled based on the behavior of merchants who gain in the market through various mode and operations. Grouping of the traders will be done based on their specific properties, and by number of candidate solution will be computed to individual merchant. First Group named as “Ruler candidate solution” afterwards its variable values are dispersed to the one more candidate solution and it named as “Serf candidate solution” In standard IEEE 14, 30, 57 bus test systems Merchant Optimization Algorithm (MOA) have been evaluated. Results show the proposed algorithm reduced power loss effectively.

9

Acoustic Attenuation Performance Analysis and Optimisation of Expansion Chamber Coupled Micro-perforated Cylindrical Panel Using Response Surface Method

Alisah Mohamad Izudin, Ooi Lu Ean, Ripin Zaidi Mohd, Yahaya Ahmad Fadzli, Ho Kelvin

Archives of Acoustics

|

2021

|

Vol. 46, No. 3

507--517

EN

This paper describes the boundary element method (BEM) and the experimental and optimisation studies conducted to understand the potential of expansion chamber coupled micro-perforated cylindrical panel (MPCP) in enhancing the acoustic attenuation for in-duct noise control issues. Owing to the complex structure of the MPCP and to achieve the correct prediction of acoustic attenuation, BEM is adopted on the basis of the Simcenter 3D software to compute the sound transmission loss (TL), As the MPCP is cylindrical in shape with numbers of sub-milimeter holes, additive manufacturing-based 3D printing is utilised for the model prototyping to reduce current design limitation and enable fast fabrication. The TL measurement-based two-load method is adopted for model validation. Subsequently, parametric studies of the MPCP concerning the perforation hole diameter, perforation ratio and depth of air space are carried out to investigate the acoustic performance. Optimisation via response surface method is used as it allows for evaluating the effects of multiple parameters as required in this study. The model validation result shows that the error between the BEM and the measured values is relatively small and shows good agreement. The R-square value is 0.89. The finding from the parametric studies shows that a wider peak attenuation can be achieved by reducing the perforation hole diameter, and one way to increase the TL amplitude is by increasing the air cavity depth. Finally, the optimised MPCP model is adopted to the commercial vacuum cleaner for verification. The sound pressure level of the vacuum cleaner is significantly attenuated within the objective frequency of 1.7 kHz.

10

Modeling of sound power transmission within duct systems

Strek Tomasz

Vibrations in Physical Systems

|

2020

|

Vol. 31, nr 3

art. no. 2020320

EN

External boundaries of acoustic devices can channel sound propagation, and in some cases can create buildup or attenuation of acoustic energy within a confined space. In this paper, it is proposed an efficient practical numerical method (based on FEM) of calculation of attenuation of sound power transmission through ducts. The method shows its viability by presenting the reasonably consistent anticipation of the experimental result. One can observe the mechanical behaviour of the duct’s medium for lower frequencies (high transmission loss) and wave behaviour for higher frequencies (small or zero attenuation). The authors proved that mechanical vibrations of medium reduce the possibility of acoustic energy transmission in duct systems. The radiation impedance for the duct is calculated as well.

11

Timber wolf optimization algorithm for real power loss diminution

Lenin Kanagasabai

Journal of Automation Mobile Robotics and Intelligent Systems

|

2020

|

Vol. 14, No. 1

24--28

EN

In this paper Timber Wolf optimization (TWO) algorithm is proposed to solve optimal reactive power problem. Timber Wolf optimization (TWO) algorithm is modeled based on the social hierarchy and hunting habits of Timber wolf towards finding prey. Based on their fitness values social hierarchy has been replicated by classifying the population of exploration agents. Exploration procedure has been modeled by imitating the hunting actions of timber wolf by using searching, encircling, and attacking the prey. There are three fittest candidate solutions embedded as α, β and γ to lead the population toward capable regions of the exploration space in each iteration of Timber Wolf optimization. Proposed Timber Wolf optimization (TWO) algorithm has been tested in standard IEEE 14, 30 bus test systems and simulation results show the projected algorithm reduced the real power loss efficiently.

12

Effect of Emergence Angle on Acoustic Transmission in a Shallow Sea

Lu Yanyang, Yang Kunde, Liu Hong, Huang Chunlong

Archives of Acoustics

|

2020

|

Vol. 45, No. 1

3--9

EN

In this study, the effect of the emergence angle of a source array on acoustic transmission in a typical shallow sea is simulated and analyzed. The formula we derived for the received signal based on the Normal Mode indicates that the signal is determined by the beamform on the modes of all sources and the samplings of all modes at the receiving depth. Two characteristics of the optimal emergence angle (OEA) are obtained and explained utilizing the aforementioned derived formula. The observed distributions of transmission loss (TL) for different sources and receivers are consistent with the obtained characteristics. The results of this study are valuable for the development and design of active sonar detection.

13

Modelowanie izolacyjności akustycznej przegród warstwowych

Majkut Leszek

Autobusy : technika, eksploatacja, systemy transportowe

|

2019

|

R. 20, nr 12

170--169

PL

W artykule, do wyznaczania izolacyjności akustycznej przegród warstwowych, wykorzystano podstawowe metody teoretycznego wyznaczania izolacyjności akustycznej właściwej przegród jednorodnych. Niezbędne do obliczeń wartości wielkości wykorzystywanych w modelach wyznaczono w wyniku homogenizacji. W pracy autor rozważania ograniczył do modeli opartych na wykorzystaniu impedancji mechanicznej przegrody. Przegrodę zamodelowano jako: bryła sztywna, odkształcalna płyta cienka (opisana modelem Kirchhoffa-Love’a) i gruba (model Mindlina-Reissnera).

EN

In the paper basic theoretical models of transmission loss calculation are described. Four different methods of homogenisation used for building of the simplified panel model are describeb. Simplified model is the single homogeneous isotropic plate panel. For this panel three impedance values of one rigid and two flexible body models of panel are described and analysed. As flexible models the thin plate (Kirchhoff-Love plate model) i thick (Mindlin-Reissner model) are analysed. All results are compared to results of 3D FEM model.

14

An Improved MSA Model for Evaluating the Sound Transmission Loss of a Rectangular Plate for Diffuse Field Incidence

Kim Myong-Jin, Won Kyong-Su, Ri Chol-Su

Archives of Acoustics

|

2019

|

Vol. 44, No. 2

259--265

EN

This paper presents an approximate analytical model for estimating the transmission loss (TL) of a finite rectangular plate in the low frequency range, which is based on the modal summation approach (MSA) taking into account the modal radiation impedance and fluid loading. The mode-dependent radiation resistance is calculated using the Rayleigh integral. The fluid loading is taken into account through the natural frequency modified by the added mass. The results are compared with the ones of Statistical Energy Analysis (SEA) coupled with FEM and FEM coupled with BEM. In addition, the effects of the various vibration modes and the fluid loading on TL, and a way for reducing the calculation time are discussed.

15

A study on the designs of the resonator for reducing resonance noise of intake system in vehicle

Xu Ch., Samoilenko D., Cho H.

Zeszyty Naukowe Instytutu Pojazdów / Politechnika Warszawska

|

2018

|

z. 1/115

5--11

EN

In the present paper, a pipe integrated resonator that can reduce the space occupation in the engine room will be introduced. A direct comparison with the Helmholtz resonator through the change of the neck will be considered as well, and possible achievement in performance improvement will be presented. In addition to the basic design of the resonator, another(an alternative) design is offered. An alternative solution suits the engine miniaturization concept taking in to account the possibility of supercharger installation. In such a case the engine compartment becomes very narrow and difficulties with the mounting of existing resonators occurs. The finite element analysis is used for the simulations of the flow processes in resonators and perforated tubes. The effects of reduction in discharge noise are reached.

PL

W niniejszym artykule zaprezentowano nową konstrukcję zintegrowanego rezonatora o zmniejszonych wymiarach, która zajmuje mniej przestrzeni w komorze silnika samochodu. Dokonano bezpośredniego porównania nowej konstrukcji o udoskonalonej geometrii z rezonatorem Helmholtza, przewidując polepszenie sprawności urządzenia. Dodatkowo do podstawowej konstrukcji rezonatora zostało zaproponowane rozwiązanie alternatywne. Alternatywne rozwiązanie spełnia wymóg minimalnych wymiarów zintegrowanego rezonatora, umożliwiając jednocześnie instalację sprężarki mechanicznego układu doładowania silnika. W omówionym przypadku przestrzeń komory silnika była by zbyt mała do zamontowania standardowego rezonatora. Wykorzystano metodę elementów skończonych do przyprowadzenia badania symulacyjnego zjawisk przepływowych w rezonatorze oraz rurach perforowanych. Uzyskano efekt zmniejszenia hałasu wskutek odprężenia powietrza w układzie dolotowym.

16

Muffler design with baffle effect and performations on transmission loss

Kamarkhani S., Mahmoudi Kohan A.

Mechanics and Mechanical Engineering

|

2018

|

Vol. 22, nr 4

1337--1343

EN

A typical sound generated by vibrational waves is usually based on the experience and design experience, which can be enhanced by optimizing the internal structure of the exhaust system. The use of baffles and perforations has a significant effect on reducing the transmission loss in a silencer exhaust system. In order to evaluate the response effect of a silencer, the effect of baffle and perforations, without baffles and perforations, was evaluated in COMSOL5.2 software. Which results in numerical results with close experimental results and the effect of buffaloes and perforations, have shown a good reduction in transmissibility, and their partial differences are due to the features of geometry design.

17

Effects of viscoelastic and porous materials on sound transmission of multilayer systems

Felhi H., Trabelsi H., Taktak M., Chaabane M., Haddar M.

Journal of Theoretical and Applied Mechanics

|

2018

|

Vol. 56 nr 4

961--976

EN

Multilayer structures allow obtaining good performance in acoustic insulation to eliminate unwanted noise in the medium and high frequencies in many applications such as building and transport industry. In this paper, the sound transmission of multilayer systems is studied using the Transfer Matrix Method (TMM). The studied multi-layered panels include elastic, viscoelastic and porous materials. Several configurations of multilayer systems are studied, and their corresponding transmission loss T L is computed. Also, the effects of porous material characteristics are studied to evaluate the impact of each parameter.

18

Modelowanie izolacyjności akustycznej przegród jednorodnych

Majkut L., Olszewski R.

Autobusy : technika, eksploatacja, systemy transportowe

|

2018

|

R. 19, nr 12

553--556

PL

W artykule opisano podstawowe metody teoretycznego wyznaczania izolacyjności akustycznej właściwej przegród jednorodnych. W pracy autorzy rozważania ograniczyli do modeli opartych na wykorzystaniu impedancji mechanicznej przegrody. Przegrodę zamodelowano jako: bryła sztywna, odkształcalna płyta cienka (opisana modelem Kirchhoffa-Love’a) i gruba (model Mindlina–Reissnera). Wartości izolacyjności akustycznej uzyskane dla tak opisanych modeli porównano dla kilku materiałów stosowanych na obudowy maszyn.

EN

In the paper basic theoretical models of transmission loss calculation are described. Here only single homogeneous isotropic panels are analysed. Three impedance values of one rigid and two flexible body models of panel are described and analysed. As flexible models the thin plate (Kirchhoff-Love plate model) i thick (Mindlin-Reissner model) are analysed.

19

Analysis and Modelling on Radiated Noise of a Typical Fishing Boat Measured in Shallow Water Inspired by AQUO Project’s Model

Peng Z., Fan J., Wang B.

Archives of Acoustics

|

2018

|

Vol. 43, No. 2

263--273

EN

The shipping noise near channels and ports is an important contribution to the ambient noise level, and the depth of these sites is often less than 100 m. However less attention has been paid to the measurement in shallow water environments (Brooker, Humphrey, 2016). This paper presents extensive measurements made on the URN (underwater radiated noise) of a small fishing boat in the South China Sea with 87 m depth. The URN data showed that the noise below 30 Hz was dominated by the background noise. The transmission loss (TL) was modelled with FEM (finite element method) and ray tracing according to the realistic environmental parameters in situ. The discrepancy between the modelled results and the results using simple law demonstrates both sea surface and bottom have significant effect on TL for the shallow water, especially at low frequencies. Inspired by the modelling methodology in AQUO (Achieve QUieter Oceans) project (Audoly et al., 2015), a predicted model applied to a typical fishing boat was built, which showed that the URN at frequencies below and above 100 Hz was dominated by non-cavitation propeller noise and mechanical noise, respectively. The agreement between predicted results and measured results also demonstrates that this modelling methodology is effective to some extent.

20

Sensor Hop-based Energy Efficient Networking Approach for Routing in Underwater Acoustic Communication

Kohli S., Bhattacharya P. P.

Journal of Telecommunications and Information Technology

|

2017

|

nr 1

44--49

EN

Underwater Wireless Sensor Networks are deployed to explore the world under the water, measure different parameters and communicate the data to the surface, in the widespread applications. The main operating technology of these networks is the acoustic communication. The communication among the sensors and finally to the surface station requires a routing protocol. The sensors being battery limited and unfeasible to be replaced under the water requires an energy efficient routing protocol. Clustering imparted in routing is an energy saving technique in sensor networks. The routing may involve single or multi hop communication in the sensor networks. The paper gives a comparative study of the benchmark protocol multi-hop LEACH with the proposed Sensor Hop-based Energy Efficient Networking Approach (SHEENA) for the shallow as well as deep water in three dimensional Underwater Wireless Sensor Networks. The network energy model for the Underwater Wireless Sensor Networks is based among the different acoustic channel characteristics. The proposed approach is found to give better response.