muffler is an important measure to eliminate aerodynamic noise and prevent dynamic noise. It is an automotive exhaust system component parts by weight, help to reduce noise pollution cars process, the principle is the use of sound waves produced by the superposition of the interference. A muffler device for reducing noise in an exhaust system mounted on the air flow passage into or aerodynamic device.
1. Muffler works
which is the principle of the muffler exhaust pipe is composed of two different lengths of pipes, the two pipes are separated again before the intersection. Half the wavelength of the acoustic wave due to the length difference is equal to two pipes emitted by motor vehicles, such that when the two sound waves cancel out each other when superimposed interference sound intensity is weakened, so that the sound is reduced, so that the effect of cancellation of the play.
resistive muffler mainly using porous sound absorbing materials to reduce noise. The sound-absorbing material fixed to the inner wall of the flow channel or arranged in a certain manner in the duct, constitute a resistive muffler. When sound waves enter the resistive muffler, part of the acoustic energy is converted into heat of friction dissipated in the pores of the porous material, so that the acoustic wave attenuated by the muffler. Resistive mufflerAs if purely resistive electrical circuit, similar to the sound absorbing material resistance. Thus, people put this muffler called resistive muffler. Resistive muffler for silencing effect in the high frequency rape, poor silencing effect of low frequency.
is a muffler tube and the chamber of the abrupt interface combination, if an acoustic filter, with similar electrical filter, each chamber is a tube with a mesh filter, a tube the mass of air equivalent to the inductance and electrical resistance, called acoustic mass and an acoustic resistance. Small volume air chamber corresponding to electrical capacitance, called acoustic compliance.
Similar to the electric filter, each cell has its own pipe with the natural frequency. When the sound waves with various frequency components into the first short tube, and only the sound waves of certain frequencies in the vicinity of the natural frequency of the first cell to a second short tube opening reaches through the mesh, while others frequencies sound wave is not possible. bounces back and forth only in a small chamber through the mesh, so, we have called this filtering function of acoustic structure acoustic filter. Select the appropriate tube and chamber combination can filter out some of the noise frequency components, to achieve the purpose of silencing. Muffler is suitable for the elimination of medium and low frequency noise.
2. Muffler Category
muffler by the muffler principle and structure can be divided muffler, resistive muffler and impedance composite muffler three
1, resistance muffler
it is also called reflection type, it is used for the majority of the original car, it need not worry about the sound absorbing cotton will fail over time, which is relatively durable. Muffler in-houseThrough the pipe, the expansion chamber separator and other components, and other kinds of noise reduction unit resonance chamber, and is reflected sound wave interference at the time of dispersal, reduced acoustic energy to achieve the purpose of the muffler. Muffler resistance band-limited, usually low, good noise reduction effect in a frequency band, high-frequency noise reduction effect is poor, use more trucks muffler.
2, resistive muffler
different shapes, not a direction of airflow. Sound absorbing material is filled in around the pipe inside the exhaust gas is absorbed by the acoustic energy reaches Muffler purposes. On, the high frequency noise cancellation effect, less pure as automobile exhaust muffler, usually in combination with a muffler used. It is a perforated pipe, the sound absorbing fibers, when the exhaust gas passes through the porous tube in contact with the fiber, and which generates vibrations by friction, viscosity and produce heat, noise in the process is to be transformed, it is also called sound absorbing process.
shaped barrier muffler has the characteristics of small volume, so the majority of the original car prefer to use the drum-shaped resistor, to its full function if the muffler, generally higher than the mounting position against the direction of the engine. A large number of tests showed that the resistive muffler of the engine, the effect of suppressing high-frequency noise it is better for the low frequency. A common case, the exhaust gas performance and resistance resistive opposite.
3, impedance composite muffler
which is characterized by both the expansion chamber, but also the sound absorbing fibers. Resistance means, respectively muffler and the muffler sound absorbing material combinations thereof, which incorporates features of the first two muffler. , Corresponding to a wide range of smaller and more flexible, but the cost is relatively high.
3. Selection and Characteristics silencer
silencer selection should be based on fire, moisture, corrosion, cleanliness requirements, installation of the spatial position of the noise source spectral characteristics, the system natural sound attenuation, the system flow noise, room allowed noise level, allowed pressure loss, equipment price and many other factors to consider and some emphasis according to the actual situation. The general situation is: the greater the noise cancellation muffler, the greater the pressure loss and price; cancellation same volume, if the pressure loss is smaller, the greater the space occupied by the muffler. New series of highly active anti-spray resistance muffler devices are widely used in power generation, chemical, metallurgical, textile factories and other industries for the various models of the boiler, turbine exhaust; security door muffler noise reducing device; fan. The muffler according to an anti-series, spray, developed resistance composite muffler principle, having a silencer volume, small size, light weight and easy installation without maintenance and many other advantages.
4. Muffler routine maintenance
1, look at the number of sump oil, from quality. Some machine hand engine oil only know how to add, to the neglect of quality checks. As everyone knows, long-term use of oil contains large amounts of oxide and metal shavings, resulting in reduced lubrication, increased wear and tear parts. Therefore, in accordance with a predetermined cycle engine oil changes regularly.
2, note that only the coupling member and the mass of the plunger coupling element of the nozzle needle, pay attention to the mass of the valve parts. First, the role of the oil valve seal, i.e. the plunger spaced from the tubing and the high pressure oil chamber, so as reflux; the second is rapid decompression when fuel cut, the fuel cut to guarantee the nozzle altogether. Good quality oil valve parts or wear after many failures will cause diesel engine. Some machine hand never clear the exhaust pipes and car muffler plotCarbon, so that carbon is too thick, the cross-sectional area of the exhaust gas is reduced, resulting in different exhaust emission, fresh air intake is insufficient, the deterioration of combustion.
3, only the maintenance of the air cleaner, the exhaust pipe and no maintenance car muffler.
4, just add water cooling, regardless of the cooling effect. Some machine hand never remove scale, although the cooling water is adequate, but the cooling effect is poor, causing a variety of problems.
5, note that only the valve seat and the valve status, pay attention to the quality of the valve spring. When the valve leak, people used to check the valves and valve seats, and valve spring quality inspection of neglect. It should be noted that the lack of valve spring tension is one of the reasons for the failure of a valve leak.