Principle and Function of Diesel Engine Muffler

The noise emitted by the diesel engine during the working process includes combustion noise, mechanical noise and exhaust noise, which are one of the main causes of environmental noise pollution. As we all know, using a muffler can effectively reduce noise, so what is the principle of a diesel engine muffler and what does it do, you will get the answer in this article.

Principle of diesel engine muffler

The main principle of the diesel engine muffler, which belongs to air intake and exhuast system, is to use porous sound-absorbing materials to reduce noise. Fixing the sound-absorbing material on the inner wall of the airflow channel or arranging it in a certain way in the pipeline constitutes a dissipative muffler. When the sound wave enters the dissipative muffler, a part of the sound energy is converted into heat energy and dissipated in the pores of the porous material by friction, so that the sound wave passing through the muffler is weakened. Dissipative mufflers are similar to electrical pure resistance circuits, and sound-absorbing materials are similar to resistors. Therefore, this kind of muffler is called a dissipative muffler. The dissipative muffler has a better muffler effect on medium and high frequencies, but has a poorer muffler effect on low frequencies.

Function of diesel engine muffler

Reactive mufflers, dissipative mufflers, and impedance composite mufflers are included into diesel engine muffler according to their working principles.

The reactive mufflers

They are also called acoustic filters, which are divided into resonance type, expansion chamber type and interference type. The simplest expansion chamber type is to connect a thick tube with a larger cross-section to the airflow channel pipe, but its terminal is a thin tube. Adjust the cross-section and length of the expansion chamber to change the reflection and interference performance of the sound wave, thereby changing the muffler and the maximum muffler frequency, which differs from a dissipative muffler in that no sound-absorbing material is placed. The advantages of the reactive muffler are simple structure, high temperature resistance, gas erosion resistance, and good low-frequency noise reduction performance. The disadvantage is that the noise reduction frequency band is narrow, and it is mainly used for the intake and exhaust ports of automobile engines and other piston engines.

The dissipative mufflers

It mainly uses sound-absorbing materials to reduce noise, and the sound-absorbing materials are fixed on the inner wall of the pipeline where the air flows or arranged in a certain way in the pipeline. When the sound wave enters the muffler, most of the sound energy is absorbed back to play a role in muffler. The advantage of the dissipative muffler is that it can muffle noise in a wide range of medium and high frequencies, especially for high-frequency sound waves; the disadvantage is that it has a shorter service life in high-temperature water vapor and gases that are corrosive. Dissipative mufflers are usually used in home, office air conditioners, large wind tunnels, jet engine test workshops, etc.

The impedance composite mufflers

Undoubtedly, the impedance composite muffler combines the advantages of the dissipative muffler and the reactive muffler. It has both dissipative sound-absorbing materials and reactive filter elements such as resonance chambers and expansion chambers inside. It has good noise reduction effect.