Development of Acoustical Simulation Model for Muffler

Hong, Tae-Whan

doi:10.21660/2016.24.1178

Cited by 2 publications

(2 citation statements)

References 9 publications

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“…In recent years, experimental and FEM studies have been used to develop efficient muffler acoustic models especially for the application of absorptive materials in noise level reduction. 17–20 For example, Munt 21 performed a transfer matrix modeling of a cylindrical exhaust muffler consisting of membrane and hard porous media to study sound propagation at low frequencies (between 63 and 500 Hz). Lee 22 investigated the acoustic performance of the exhaust at frequencies below 3000 Hz using FEM.…”

Section: Introductionmentioning

confidence: 99%

Effects of inlet-outlet positioning, muffler geometry, and baffle design on vehicle muffler performance for desired sound transmission loss

Ebrahimi-Nejad

Rahimi

Kheybari

et al. 2022

Proceedings of the Institution of Mechanical Engineers, Part D:

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A systematic comparative examination of different single-chamber and double-chamber muffler geometries, comprised of various baffle geometry and size, number of chambers, and inlet-outlet positioning was conducted to determine the most suitable geometry for size-efficient mufflers which can meet size-limitations of automotive applications, confirming enhanced transmission loss (TL). First, we considered a reference model for validation of the simulation method. Then, we objectively studied the effects of circular and rectangular baffles of different sizes on the TL of single-chamber mufflers. Next, double- and single-chamber models were compared. Consequently, to better analyze the performance of the representative benchmark double-chamber muffler, the effects of different layouts of the outlet were studied and the corresponding TL was derived, while the inlet and baffle type and size were fixed. Finally, the effect of inlet layout, considering given outlet position, baffle type, and size, was studied on the noise control performance of the muffler. Results indicate that the 75% circular baffle has a wide frequency range and high TL of 58 dB, where the 75% rectangular plate baffle has a transmission loss of 67 dB. The double-chamber muffler has a wider frequency range and a higher TL of 78 dB compared to the single-chamber muffler. Moreover, changes in the inlet-outlet of the silencer significantly affect TL. As the inlet-outlet positioning of the silencer greatly contributes to the space constraints and packaging of the vehicle components, therefore, the variations of the inlet-outlet position of the silencer in the limited space available in vehicles need to be considered as an important design parameter, considering packaging limitations and noise control performance, which can significantly affect tailpipe radiated noise.

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Section: Introductionmentioning

confidence: 99%

Effects of inlet-outlet positioning, muffler geometry, and baffle design on vehicle muffler performance for desired sound transmission loss

Ebrahimi-Nejad

Rahimi

Kheybari

et al. 2022

Proceedings of the Institution of Mechanical Engineers, Part D:

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“…Vortex flow can be introduced in fluid systems by modification of the path of flow in order to achieve desired effects. Such modifications include introduction of holes with sharp edges [2], barriers in the path of flow [3], or sudden contraction or expansion as is the case with the SEC [4]. Applications of this phenomenon in vortex motion have been successfully studied by Smith et al, [5] who identified two scattering mechanisms that allow neighbouring modes to interact; scattering occurs at significantly lower frequencies when the mean flow is present; an exchange of energy between mean flow and acoustic field occurs during scattering.…”

Section: Introductionmentioning

confidence: 99%

Effects of Central Tube on Shape of Modal Duct of a Helicoid in a Simple Expansion Chamber

Onyango

Kinyua

Mayaka

2018

Advances in Acoustics and Vibration

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The shape of the modal duct of an acoustic wave propagating in a muffling system varies with the internal geometry. This shape can be either as a result of plane wave propagation or three-dimensional wave propagation. These shapes depict the distribution of acoustic pressure that may be used in the design or modification of mufflers to create resonance at cut-off frequencies and hence achieve noise attenuation or special effects on the output of the noise. This research compares the shapes of acoustic duct modes of two sets of four pitch configurations of a helicoid in a simple expansion chamber with and without a central tube. Models are generated using Autodesk Inventor modeling software and imported into ANSYS 18.2, where a fluid volume from the complex computer-aided-design (CAD) geometry is extracted for three-dimensional (3D) analysis. Mesh is generated to capture the details of the fluid cavity for frequency range between 0 and 2000Hz. After defining acoustic properties, acoustic boundary conditions and loads were defined at inlet and outlet ports before computation. Postprocessed acoustic results of the modal shapes and transmission loss (TL) characteristics of the two configurations were obtained and compared for geometries of the same helical pitch. It was established that whereas plane wave propagation in a simple expansion chamber (SEC) resulted in a clearly defined acoustic pressure pattern across the propagation path, the distribution in the configurations with and without the central tube depicted three-dimensional acoustic wave propagation characteristics, with patterns scattering or consolidating to regions of either very low or very high acoustic pressure differentials. A difference of about 80 decibels between the highest and lowest acoustic pressure levels was observed for the modal duct of the geometry with four turns and with a central tube. On the other hand, the shape of the TL curve shifts from a sinusoidal-shaped profile with well-defined peaks and valleys in definite multiples of π for the simple expansion chamber, while that of the other two configurations depended on the variation in wavelength that affects the location of occurrence of cut-on or cut-off frequency. The geometry with four turns and a central tube had a maximum value of TL of about 90 decibels at approximately 1900Hz.

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Development of Acoustical Simulation Model for Muffler

Cited by 2 publications

References 9 publications

Effects of inlet-outlet positioning, muffler geometry, and baffle design on vehicle muffler performance for desired sound transmission loss

Effects of inlet-outlet positioning, muffler geometry, and baffle design on vehicle muffler performance for desired sound transmission loss

Effects of Central Tube on Shape of Modal Duct of a Helicoid in a Simple Expansion Chamber

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