Experimental and theoretical studies of resonance phenomena in a silencer for a low-power ICE

Аuthors

Sukhovaya E. A.

Kazan National Research Technical University named after A.N. Tupolev, Kazan, Russia

Abstract

This article provides an overview of the computational methods used in the design of ef- fective silencers for an ICE exhaust system. It presents a numerical calculation in the ANSYS Fluent software package of a two-chamber silencer with a transverse partition and an annular gap for a low-power ICE. During the modeling of gas-dynamic processes in the silencer, it was necessary to determine its resonant frequencies at which there is a picture of sharp noise amplification. The construction of a three-dimensional geometric model of the silencer, on which the computational grid was applied, was carried out using the Gambit program. The following boundary conditions were specified: the mass flow rate of air, the intensity of tur- bulent pulsations and the hydraulic diameter were indicated at the inlet to the silencer; and constant atmospheric pressure was indicated at the outlet from the silencer. In this case, the pulsating pressure was taken as a sinusoidal function. The RNG k-ε turbulence model was used to model the gas-dynamic processes along the silencer path. According to the data ob- tained, a graph of the dependence of the amplitude of fluctuation of a pulsating pressure at the outlet of the silencer to the amplitude of fluctuation of a pulsating pressure at the inlet versus the frequency of fluctuation a pulsating pressure was plotted. This graph shows the resonance phenomena at frequencies of 50 Hz and 74 Hz. In order to verify the adequacy of the compu- tational model, experimental studies were carried out on a special installation in the form of a sound-absorbing chamber with a source of harmonic sound vibrations, the silencer and measuring equipment. Based on the experimental data, a graph of the dependence of the amp- litude of sound pressure at the output and input of the silencer on the pressure frequency of fluctuation was also constructed, clearly showing both manifested resonant frequencies, 55 Hz and 74 Hz, and their correspondence to the theoretical results. Considering the silencer under study as a Helmholtz resonator, its resonant frequencies were also calculated using the empirical Helmholtz formula. On the basis of the coincidence of the calculated values of the resonant frequencies with theoretical and experimental values, it was found that the proposed theoretical model for investigating a low-power engine silencer allows calcu- lateng the resonant frequencies with an accuracy of 95%.

Keywords:

silencer, low-power ICE, RNG turbulence model, Helmholtz resonator, resonant frequency.

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