Page 264 - Mechanic Diesel - TT

MECHANIC DIESEL - CITS

MODULE 12 : Emission Control System

LESSON 80 - 83: Emission control system Definition,
Sources of emission & Its Methods

Objectives

At the end of this lesson you shall be able to
• define emission control system
• find sources of emission and its methods.

Emission Control System: definition, source of emission (such as exhaust system, crank case, fuel tank
and carburettor)
Emission Control System: In the automobile sector, pollutants are emitted into the atmosphere through the fuel
tank, carburetor, crankcase and exhaust system. Fuel vapor is emitted from the fuel tank and carburetor, while
half-burnt air-fuel mixture is emitted from the crankcase through the piston and rings, and half-burnt hydrocarbons,
carbon monoxide, nitrogen oxides and Sulphur oxides are emitted through the exhaust system. Apart from this,
particulate matter also forms a major part of the exhaust emissions in diesel engines.

Particulate matter, apart from water, also includes those substances which are obtained by filtering the exhaust
gas. Some unburnt hydrocarbons are absorbed on the smoke and carbon-containing particulate matter.
Exhaust system: The internal combustion engine of a car is the source of its power. It burns fuel along with air in
order to create hot gases at high pressure that drives a piston with their force. During this process, the toxic gases
that are some of the products of this combustion would be emitted into the atmosphere were it not for the car’s
exhaust system. The exhaust system of a vehicle has several important functions, which include the purification
of the toxic gases and the reduction of engine noise. Without an exhaust system, cars would create both noise
and air pollution that would be as dangerous as it is unpleasant

Fuel tank: To fill the fuel, diesel vehicles have a diesel tank installed above the engine assembly. It is made of
strong metal sheet in round or square or other convenient designs. There is enough space to fill diesel in it, which
has a lid on it. There is a union fitted at the bottom of the tank, through which the diesel, with the help of pipes,
goes to the filter or fuel transfer pump. Diesel tanks are constructed from sheet metal with oil seams and a special
coating of glass or fiber glass reinforced plastic metal is applied to protect against corrosion. Other contaminants
found in diesel also keep accumulating in this sediment chamber. Another electrical device is installed on top of
this tank, through which the amount of fuel in the tank is detected through the gauge installed on the dashboard.
There is also a provision of installing a pipeline on the tank to bring the excess fuel coming from the injectors back
to the tank, which is called an overflow pipeline.

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