In this article, you’ll learn about types of mufflers, working, design.
Mufflers and Types
If the high-pressure exhaust gases were allowed to enter the atmosphere directly from the exhaust manifold, a loud unpleasant noise would be heard like the firing of a gun.
This noise is due to the large difference in pressure between the exhaust gases and the atmosphere.
For quite an operation of the motor vehicle, it is desirable to reduce (or silencer) in the exhaust system. A muffler is connected between the engine exhaust pipe and the tail or outline pipe.
What is Muffler?
The function of the muffler is to reduce the pressure of the exhaust gases sufficiently to permit them to be discharged to the atmosphere silently. The reduce the pressures the exhaust gases are permitted to expand slowly and to cool in the muffler.
The capacity of the muffler should be sufficiently large to permit the gases to expand to nearly atmospheric pressure before they are discharged into the air.
Also, the muffler should not have any appreciable restriction, to flow that will raise back pressure excessively.
In some designs, the outer shell of the muffler is made oval in shape to permit adequate clearance with the ground.
Many of the outer shells of mufflers are made of steel coated with lead-tin alloy or aluminum to resist corrosion, particularly that caused by the exhaust condensate.
Most of the mufflers are provided with small drain holes in the outside shell to drain out the condensate from the exhaust gases and to resist corrosion.
Types of Mufflers
Following are the different types of mufflers used in vehicles:
- Baffle type muffler
- Wave cancellation type muffler
- Resonance type muffler
- Absorber type muffler
- Combined resonance and absorber type muffler
#1. Baffle Type Muffler.
It consists of a number of baffles spot welded inside the cylindrical body. the purpose of these baffles is to close the direct passage of the exhaust gases, thus the gases travel a longer path in the muffler.
There are many designs of the baffles used in the muffler. The image shows two types of such mufflers which have low efficiency. Due to the restricted flow of the exhaust gases, back pressure increases causing the loss of engine horsepower.
#2. Wave Cancellation Type Muffler.
In this type of muffler, the exhaust gases entering the mufflers are divided into two parts to flow in the muffler. The lengths of these paths are so adjusted that after they come out of the muffler, crests of one wave coincide with the troughs of the second wave.
Thus cancelling each other and reducing noise to zero theoretically. This is achieved if the lengths of the two paths differ by half the wavelengths.
But this is not achieved practically, because the noise produced by exhaust gases is a combination of different frequencies at different engine speeds. However appreciable noise is reduced.
#3. Resonance Type Muffler.
It consists of a number of Helmholtz resonators in series through which a pipe having access port passes.
Helmholtz is the name of a person who originated the idea of this type of muffler. The exhaust gases flow through this pipe. This resonator eliminates the fundamental and higher harmonics of the engine noise.
#4. Absorber Type Muffler.
It consists of a perforated tube, around which a sound absorbing the material like fiberglass or steel wool is placed.
The exhaust gases pass through the perforated tube. the sound-absorbing material reduces the high-pressure fluctuation of the exhaust gases thus reducing the noise intensity.
These mufflers may be either straight-through type or reverse flow type, as shown in the figure.
#5. Combined Resonance and Absorber Type Muffler.
Sometimes, a resonance chamber is provided at one end or in the noddle of the straight through absorber type muffler, to reduce the pressure and noise still further.
In some designs, a resonance chamber is a separate unit called a resonance, which is connected in series to the muffler.