What are the types of exhaust muffler？

We all know that the noise of traditional agricultural tractors is relatively large. The noise mainly comes from diesel engines and exhaust pipes, but the noise of small cars is very small. Why? On the one hand, a lot of sound-absorbing materials are installed in the engine compartment of the car; on the other hand, the exhaust muffler is installed in the car.

This article contains the following:

• Noise elimination method of exhaust muffler

• Resistive muffler

• Resistant muffler

• Impedance compound muffler

• Micro-perforated plate muffler

• Small hole muffler

• Active muffler

1.Noise elimination method of exhaust muffler

Absorption and muffler method: Absorption muffler reduces the energy of exhaust gas by friction on glass fiber, steel fiber and asbestos and other sound absorbing materials.

Reflective muffler: reflective muffler has multiple series-tuned chambers and porous reflector tubes of different lengths connected to each other. Exhaust gas undergoes multiple reflections, collisions, expansions and cooling to reduce its pressure, reduce vibration and energy.

2.Resistive muffler

This type of muffler contains porous tubes and sound-absorbing fibers. When the exhaust gas passes through the latter, it generates vibration and generates heat energy due to friction and stickiness. The noise is converted in this process, so it is also called sound absorption. process. The specific shape of the resistive muffler is different, and the airflow direction is also different.

The muffler has a small size, so most of the original car's middle drums like to use the muffler. If you want to make full use of its muffler function, the installation position is generally closer to the direction of the engine. A large number of tests have shown that the resistance of the muffler to the bow | engine medium and high frequency noise is better than its medium and low frequency. In the same situation, the performance of resistant exhaust is just the opposite of resistance.

3.Resistant muffler 

There is no sound-absorbing cotton in the structure of this type of muffler, which is mainly composed of baffles and expansion chambers. The general muffler has three expansion chambers of different sizes. The exhaust gas is reflected in these chambers and interferes with each other (friction) to achieve the noise reduction effect. The large chamber is more conducive to its handling of noise, but its size is also limited by the shape of the chassis. Advantages in this regard.

In addition, the working mode is different, the volume of the resistant muffler is larger than the resistance, so it is often installed at the rear of the vehicle. The obvious characteristics of medium and low frequency noise suppression effect help it to please many original car manufacturers. An "acoustic filter" composed of tubes and chambers with abrupt interfaces to reduce noise;

4.Impedance compound muffler

The structure of the compound muffler combines the characteristics of the first two mufflers, that is, it has both sound absorption cotton and expansion chamber. As mentioned above, the two mufflers have different lengths and compound each other when they correspond to the bow | engine speed. The shape is a good balance between the two characteristics, the corresponding range is wide, the volume is more flexible, but the cost is relatively high.

Most car modification circles use resistance type and compound type mufflers, which are somewhat related to the exhaust back pressure. In China, on the basis of the composite tail drum, the shape of the porous tube in the muffler is divided into S drum, G drum, H drum, etc.

5.Micro-perforated plate muffler

This type of muffler is a muffler lined with micro-perforated plate structure. It can eliminate airflow noise in a wide frequency range, and has high temperature resistance, oil resistance, and corrosion resistance. Even if there is a lot of moisture in the airflow, it will not affect the work. Because the diameter of the perforation is small and the surface of the board is smooth, the resistance loss of the muffler is smaller than that of the general resistance muffler.

The micro-perforated plate muffler is generally made of a pure metal thin plate with a thickness of less than 1mm. The thin plate is perforated with a drill with an aperture of less than 1mm. The perforation rate is 1% to 3%. By selecting different perforation rates and different cavity depths, the spectrum performance of the muffler can be controlled so that it can obtain a good muffling effect within the required frequency range.

6.Small hole muffler

The structure of this type of muffler is a straight tube with a closed end, and many small holes are drilled in the wall of the tube. The principle of the small hole silencer is based on the spectrum of jet noise. If the total area of the nozzle is kept constant and replaced by many small nozzles, when the airflow passes through the small hole, the spectrum of the jet noise will move to high frequency or Ultra-high frequency makes the audible sound component in the spectrum significantly lower, thereby reducing interference and harm to people.

The small-hole muffler has a low-medium-frequency broadband muffler performance, a small aperture can increase the sound absorption coefficient, a low porosity can increase the width of the sound absorption band, and the depth of the orifice plate can change the position of the resonance absorption peak. The small-hole muffler has the advantages of strict design, absorption frequency bandwidth, small resistance loss, high temperature resistance and long life. It is generally used to vent the exhaust of high-pressure equipment such as boilers and compressors.

7.Active muffler

This muffler is a set of instruments, mainly composed of microphones, amplifiers, phase shifting devices, power amplifiers and speakers, etc., by generating sound waves equal to the original sound pressure and opposite phase to cancel the sound waves in the original sound field, thereby Certain noise reduction effect.

Active mufflers are widely used in power plants, chemical industry, metallurgy, textiles and other industrial plants and mines for various types of boilers, steam turbine exhaust; fans; safety doors and other equipment for noise reduction and sound reduction.

If you want to buy exhaust mufflers,please contact GRWA.