Design and demonstration of composite mufflers based on dissipative and reactive units

Abstract

We have proposed and validated a design of a composite muffler. By a combination of dissipative and reactive units with different operating mechanisms, the advantages of both structures are utilized to achieve high transmission loss (TL) from low to high frequency in the ventilation duct system. A dissipative muffler composed of porous sound absorbing materials (PSAM) is chosen for noise attenuation above 1000 Hz, and a reactive muffler composed of Helmholtz resonators is used to reduce the noise below 1000 Hz. The combination of the two can achieve a TL above 20 dB in the broadband range of 244-1600 Hz and up to 30 dB in the vast majority of the frequency band, demonstrating excellent noise reduction effect. The proposed composite muffler has great advantages in broadband noise reduction for ventilation systems.

The Influence of the Frequency of Ultrasound on the Exhaust Gas Purification Process in a Diesel Car Muffler

“…where Q is the capacity of the combustion chamber and R is the average radius of the muffler. By replacing ϑ in Equation ( 15) with expression (19), we obtain…”

“…GTR 15 includes the particle number methodology for light-duty vehicles without emission limits, making it the sole Global Technical Regulation to do so [18]. The main toxic components of gases are carbon oxides (CO) [4], hydrocarbons (CH), nitrogen oxides (NO x ) [19], soot (heavy metals) [20], carbon black, soot, etc. The requirements for the toxicity of exhaust emissions from new cars were set by law and modeled from the "Euro" regulations to solve the problem of air pollution from exhaust gases in most countries.…”