Page 103 - Mechanic Diesel - TT

MECHANIC DIESEL - CITS

Thus, silencers that reduce low and high frequency noise should be used in vehicles. Following types of mufflers
are used in vehicles as per requirement.

i Reactive Muffler: In this type of muffler, the inlet and outlet tubes extend towards the chamber, hence this
muffler is also known as chamber muffler. Usually it consists of many types of pipe segments, which are
connected together by a large chamber. These reduce the sound generated by combustion through destructive
interference. In other words, these pipe segments divide the sound produced and reduce its value. These
mufflers are very helpful in reducing low frequency sound; Such as Midas, Drift Tech, Full Bore etc. Nowadays
only reactive mufflers are used in trucks.

ii Absorptive muffler: In this type of muffler, absorbing materials are used to reduce the noise generated by
the combustion process. Due to this method, the sound waves are reduced and the energy in the absorbent
material is converted into heat.
In absorbent muffler, two functions are accomplished, destruction of more energy due to higher coefficient and
generation of less radiated sound waves.
Types of absorptive muffler
Three types of absorptive muffler
A Straight thorough muffler: This is the easiest way to reduce the sound generated by the gases coming
out of the cylinder. In this, a pipe is fitted across the muffler housing. Holes are cut in it. This pipe is closed
from the middle. the burnt gases from the exhaust manifold pass through this pipe and fill the housing.
From this housing again these gases come out without any pressure and sound through the holes of the
pipe at the other end. Due to the holes in this pipe, entry and exit of gases occurs slowly due to this, the
velocity and pressure of these gases gets lost.
B Reverse flow type: In this type of muffler, separate compartments or chambers are made and each
chamber is connected to each other, due to which the burnt gases in the muffler are taken out through
many curved parts. Due to this rotation, the velocity and pressure of the burnt gases are lost and the gases
come out without any sound.

C Baffle plate type: In this type of muffler, baffle plates with one or two holes are used inside the housing.
When the gases coming out of these plates collide, their velocity and pressure reduce, due to which the
burnt gases come out without any sound.

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CITS : Automotive - Mechanic Diesel - Lesson 25 - 28