scholarly journals Tuning a Two-Chamber Muffler for Wide-Band Transmission Loss

2020 ◽  
Vol 25 (2) ◽  
pp. 248-253
Author(s):  
M.L. Munjal
Keyword(s):  
Transmission Loss ◽  
Velocity Ratio ◽  
Low Frequency ◽  
Wide Band ◽  
Firing Frequency ◽  
Automotive Exhaust ◽  
Expansion Chamber ◽  
Significant Term ◽  
Wide Band Transmission ◽  
Exhaust Noise

The design of a muffler with wide-band transmission loss (TL) is a basic requirement for automotive exhaust systems where the exhaust noise is spread over several harmonics of the engine firing frequency. This has led to the concept of a double-tuned expansion chamber. In the present paper, the concept of double-tuning is extended to the two-chamber mufflers. The author's classical Velocity Ratio Algorithm is used here to analyze and design such a muffler. The relevant two-row array is manipulated and simplified to arrive directly at the single most significant term out of the 81 non-dimensional terms constituting the relevant Velocity Ratio. Examination of this single term reveals acoustics of the raised wide-band domes of the TL spectrum of the double-tuned two-chamber (DT2C) muffler vis-a-vis that of an equivalent longer double-tuned single-chamber muffler. Except for a low-frequency trough, its TL curve covers the entire frequency range of interest for control of automotive exhaust noise. It is also shown that the corresponding side-inlet side-outlet (SISO) DT2C muffler configuration has an identically similar wide-band TL spectrum to that of the co-axial muffler configuration. Finally, some guidelines are laid out for designing a DT2C muffler.

A Study on Exhaust Muffler Using Counter-Phase Counteract

2014 ◽  
Vol 986-987 ◽  
pp. 810-813
Author(s):  
Ying Li Shao
Keyword(s):  
Mathematical Model ◽  
Experimental Validation ◽  
Noise Source ◽  
Low Frequency ◽  
Frequency Noise ◽  
Expansion Chamber ◽  
Band Noise ◽  
Exhaust Noise ◽  
Perforated Pipe ◽  
The Mathematical Model

The exhaust noise, which falls into low-frequency noise, is the dominant noise source of a diesel engines and tractors. The traditional exhaust silencers, which are normally constructed by combination of expansion chamber, and perforated pipe or perforated board, are with high exhaust resistance, but poor noise reduction especially for the low-frequency band noise. For this reason, a new theory of exhaust muffler of diesel engine based on counter-phase counteracts has been proposed. The mathematical model and the corresponding experimental validation for the new exhaust muffler based on this theory were performed.

Acoustic performance analysis of Helmholtz resonators with conical necks and its application

2019 ◽  
Vol 67 (3) ◽  
pp. 155-167 ◽  
Author(s):  
Haitao Liu
Keyword(s):  
Finite Element ◽  
Prediction Model ◽  
Transmission Loss ◽  
Low Frequency ◽  
Wide Band ◽  
Acoustic Properties ◽  
Frequency Range ◽  
Acoustic Attenuation ◽  
Acoustic Performance ◽  
Helmholtz Resonators

The acoustic properties of the Helmholtz resonators with conical necks, which have broad acoustic attenuation band performance in the low frequency range, are investigated in this study. In order to investigate its wide-band acoustic attenuation mechanism, three-dimensional finite element models for the Helmholtz resonators with different necks are built respectively. The acoustic performance prediction model based on the one-dimensional analytical approach with acoustic length corrections is built to calculate the transmission loss results more efficiently, and the formula for calculating the resonance frequency is also derived. Then, the prediction model and the formula are verified by finite element method and experiment, which show good agreements. As a result, the prediction model is applied to analyze the sound attenuation properties of the Helmholtz resonators with conical necks, and the results show that the acoustic attenuation bandwidth in the low frequency range is improved by increasing the taper angle of the neck. At last, the approaches for the Helmholtz resonators with conical necks are applied to design an actual middle silencer of a passenger car. The results show that the designed middle silencer performs much better than the original one, which can effectively eliminate the exhaust order noise to meet the standard of exhaust noise control. The test results fully reveal that the Helmholtz resonators with conical necks in the muffler can play a better role in eliminating exhaust order noise, and the approaches proposed in this article can effectively guide the design of Helmholtz resonators with conical necks.

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.

A Study on the Acoustic Characteristics of the Counter-Phase Muffler

2011 ◽  
Vol 130-134 ◽  
pp. 41-44
Author(s):  
Ying Li Shao
Keyword(s):  
Experimental Validation ◽  
Noise Source ◽  
Low Frequency ◽  
Frequency Noise ◽  
Expansion Chamber ◽  
Acoustic Characteristics ◽  
Band Noise ◽  
Exhaust Noise ◽  
Perforated Pipe ◽  
The Mathematical Model

The exhaust noise, which falls into low-frequency noise, is the dominant noise source of a diesel engines and tractors. The traditional exhaust silencers, which are normally constructed by combination of expansion chamber, and perforated pipe or perforated board, are with high exhaust resistance, but poor noise reduction especially for the low-frequency band noise. For this reason, a new theory of exhaust muffler of diesel engine based on counter-phase counteracts has been proposed. The mathematical model and the corresponding experimental validation for the new exhaust muffler based on this theory were performed.

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