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Treating The Exhaust gas in IC Engine - Air Injection System

Treating the exhaust gas means some cleaning or reducing the percentage of pollutants in it. It takes place after leaving the exhaust gas from the engine cylinders and before it exists the tail pipe and enters the atmosphere. It reduces the amount of HC, CO and No2 in the exhaust gas. The exhaust gas is treated in two ways. One is by injecting fresh air into the exhaust system. The other is by sending the exhaust gas through catalytic converter.

1) Air Injection System :

   The main parts of an air-injection system are the air pump, one way check valve and piping into the exhaust main fold. The air pump is driven by a belt from the crank shaft pulley. When the engine is cold, air is supplied to exhaust manifold. This fresh air supplies excess oxygen to oxide of HC and CO into CO2 and water vapor. 



The diverter valve presents back-firing in the exhaust system. The diverter valve is operated by a vacuum diaphragm. When the fuel Injection system is in idling or in part or full throttle conditions, the manifold vacuum is not enough to move the diverter valve diaphragm. But, on sudden decelerations manifold vacuum will increase. This will lift in the diaphragm and send the air to the atmosphere or air cleaner. 

High manifold vacuum draws rich mixture from the carburetor. It is too difficult to ignite in the combustion chamber due to which reasons, it goes out in the exhaust manifold.

When air pumped into exhaust manifold, the mixture becomes lean. It would ignite when hot exhaust gases are released from the next cylinder. This may result in back firing. To prevent this, the diverter valve diverts the fresh air from exhaust manifold during deceleration. Check valve is meant to prevent back flow whenever exhaust pressure is greater than air pump pressure.  



 


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