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Tuning the selected acoustic helicoidal resonator with a short flat bar - numerical analysis

Łapka Wojciech

Vibrations in Physical Systems

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2019

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Vol. 30, nr 1

art. no. 2019140

EN

This paper describes the possible way of tuning the selected acoustical helicoidal resonator placed in straight cylindrical duct by the use of a short flat bar. The acoustic attenuation performance (transmission loss) of helicoidal resonator has emphatically changed with the change of the length and the degree of rotation of a short flat bar placed close to the resonator. The finite element numerical calculations of the acoustical systems were made in COMSOL Multiphysics computational environment. The results show that the change of length and rotation of short flat bar can widely change the resonance frequencies of helicoidal resonator. So in this work were presented the possible simple tuning options for the acoustic helicoidal resonator applied in ducted systems.

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Numerical Study of Acoustic-Structure Interaction of Selected Helicoidal Resonator with Flexible Helicoidal Profile

Łapka W.

Archives of Acoustics

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2018

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Vol. 43, No. 1

83--92

EN

The paper presents the results of numerical studies of acoustic-structure interaction of selected helicoidal resonator with helicoidal profile made of an elastic material. Considered a well-recognized acoustic system for one representative type of acoustic helicoidal resonator with two resonant frequencies that correspond to previous studies of the author. Due to the large range of flexible materials to study, this work focuses on the change of material density, Poisson’s ratio and Young’s modulus as the basic parameters describing the properties of elastic materials. The results indicate a significant interaction between the acoustic attenuation performance of helicoidal resonator and elasticity of the helicoidal profile. These interactions are most evident in the frequency range in which the helicoidal resonator is revealed to be effective acoustic damper.

3

Selected aspects of modeling mufflers for exhaust systems of vehicles

Gągorowski A., Melon A.

Journal of KONES

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2013

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Vol. 20, No. 2

97--103

EN

The world used several solutions exhaust systems of motor vehicles. Today, in addition to the core function of which is to discharge exhaust gases from a combustion engine and noise reduction, these systems must comply with the functions associated with aftertreatment and impact on the characteristics of the engine. Requirements increase for noise suppression, at the tendency to increase engine efficiency and reduce fuel consumption. On the other hand, it seeks to reduce production costs. All this forces the search for new solutions and improve existing ones. In the process of the combustion gases discharge it is also important to eliminate frequency bands especially harmful to people and the environment (including other living organisms). Our goal is to develop a new design muffler of exhaust system that will meet these expectations of producers and users of vehicles. For this purpose, mathematical analysis of a classical systems with circular holes in the perforated pipes and proposed by the authors of the longitudinal gaps systems was performed. The paper presents some aspects of mufflers modeling for reducing acoustic noise emitted from the vehicle. Basic criterion for assessing was therefore the damping effect. Built theoretical models have allowed a rough estimate of acoustic performance at specific frequency bands by determining the transfer impedances. Because the noise reduction in automobiles is a complex, for the construction of such systems one of the important elements is to eliminate these frequency bands of acoustic waves in the process of the exhaust gases discharge which are the most dangerous to humans. The comparative analysis of these systems has allowed to determine the direction of further structural changes.