1. Muffler
Automobile mufflers are components commonly used in automobiles, help to reduce noise pollution vehicle is in motion, the use of sound waves is made of the principle of superposition interference. Principle
automotive muffler
principles automobile muffler exhaust pipe which is to be comprised of different lengths of two pipes, the two pipes are separated first and then 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 muffler as if purely resistive electrical circuit, similar to the sound absorbing material resistance. Thus, people put this muffler called resistive muffler. Resistive muffler of high-frequency noise cancellation effect is good, the poor low-frequency noise cancellation effect.
the muffler by the muffler are abrupt interface tube and chamber combination, if an acoustic filter, with similar electrical filter, each chamber is a tube with a mesh filter tube in air quality 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. And electrically similar to a 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 sonic is not possible through the mesh. Only reflected back and forth in a small chamber, so we call this include filtering of acoustic structure acoustic filter. SelectThe tube and the chamber suitable combination. You can filter some noise frequency components, to achieve the purpose of silencing. Muffler is suitable for the elimination of medium and low frequency noise.
The structure and barrier structure in accordance with a certain resistance in combination together, constitute the impedance complex muffler.
Micro-perforated plate muffler is generally less than a thickness of 1mm is made of pure metal sheet, on the sheet with a pore diameter less than 1mm drill boring the perforations 3 a percentage rate of 1 percentage. Select different thickness and different perforation rates deep cavity, you can control the spectral performance of the muffler, so as to obtain good silencing effect in the desired frequency range.
muffler structure is an aperture closed end of the straight tube, there are many small holes drilled on the wall. Is based on the principle muffler hole jet noise spectrum is based, if the spout to keep the total area of the same but with many small jets instead, when the air flow through the holes, jet noise spectrum will move to ultra-high frequency or a high frequency, so that the audible sound component spectrum significantly reduced, thereby reducing interference and human harm.
The basic principle of the active silencer in the original sound field, using the electronic device then generates a equal to the original sound pressure magnitude and opposite phase acoustic wave, so that the original sound field offset within a predetermined range . This instrument is a muffler apparatus, primarily by the microphone, amplifier, phase shifting means, a power amplifier and a speaker and so on.
The main structure automobile muffler
car muffler according to the principles muffler and structure can be divided muffler, resistive muffler and impedance composite muffler three [ 123]
1. muffler
muffler by the muffler unit when various pipes, separators and other components expansion chamber, the resonance chamber and so on, when the sound wave is reflected and propagated in the interior interference, reducing the 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
is filled with sound absorbing material around the pipe inside the exhaust gas is absorbed by the acoustic energy reaches Muffler purposes. For medium and high frequency noise elimination effect, simply useFor automotive exhaust mufflers less, usually in combination with a muffler used together.
3. Muffler complex impedance
are respectively resistant muffler and the muffler unit composed of a combination of sound absorbing material, having common characteristics resistant, resistive muffler. Low, medium and high frequency noise has a very good noise cancellation effect.
major role
muffler
reducing the exhaust noise of the engine, and the high temperature exhaust gas can be discharged safely and effectively. As part of the muffler of the exhaust duct, which should ensure the smooth flow of the exhaust gas, small resistance and sufficient strength. Muffler subjected to 500 ℃ ~ 700 ℃ temperature exhaust gas, to ensure that within a predetermined mileage automobiles, no damage, no loss of noise reduction effect.
car muffler using realistic
Automobile noise is mainly from vehicle exhaust noise. If left muffler, at a constant speed, the noise up to 100 decibels. When more than when followed by engine noise and tire noise, engine noise during normal operation of the car, up to 90 decibels, and tire noise at speed of 90 km / h, up to 95 decibels. Thus, with a muffler in the exhaust system, exhaust noise reduction can make the cars 20-30 dB. In the engine, a gasoline engine for the diesel engine, the engine noise can be reduced 6-8 dB.
Common Faults and exclusion
Failure phenomenon: a Dongfeng EQ1090D cars muffler appears blasting phenomenon in motion, stop and check, when the ignition coil high voltage total FireWire unplug the cylinder at a distance of 34mm at the test fire, pulled off contact distributor or crank crank, flashover were normal, but found that the distributor contacts have de-energized ablation phenomenon. Grinding contact with the sand bar and adjust the gap to 0.35-0.45mm, the engine starts running normally, but when the car traveling about 40 kilometers, muffler blasting phenomenon has emerged.
Troubleshooting and exclusion: according to the above-described phenomenon muffler blasting careful analysis of the reasons for the failure to identify the crux checked firing order, distributor contact spring force of the arm off the ignition timing, spark plug, etc. no problems found. Continue checking the carburetor air filter, also not lash results. againTimes and start the engine in normal operation, but did not take long old disease relapse.
stop again check the distributor portion. By removing and careful examination, finally found breaker contact arm to the low pressure terminal of the copper paste line bend fracture, only a few fine copper wire were connected. After replacing the copper paste broken line, the fault disappears.
Failure Analysis: When the distributor part of a low pressure copper wire breaking wire cross-section is reduced, thereby increasing the resistance of the primary circuit, the circuit current is reduced, resulting in insufficient high voltage ignition coils. When the engine temperature is low, although more difficult to start, but after starting the engine can operate normally. After the engine temperature increases, a rise in temperature of the ignition coil, and the resistance increases with increasing temperature, the high voltage generated by the ignition coil will be more insufficient, weaker high voltage spark, or even misfire. From time to time misfiring cylinder in not ignited combustible mixture into the muffler, when the expansion of the muffler, exhaust gas encountered in the deflagration of Mars that is, the performance of the muffler blasting.