Exhaust Gas Recirculation |
Exhaust gas recirculation is a new way of reducing NOx(nitrous oxides) emissions in Automobiles. Before we begin on how to reduce emissions of NOx, we will first understand the reason for the emission of NOx in the first place.
NOx is a result of the combustion of petroleum fuels in the combustion chamber. They are the result of the high combustion temperatures that are reached within the chamber. The emission of NOx increases with increase in the combustion temperature in the engine. NOx is very harmful to the environment, thus techniques like EGR or exhaust gas recirculation are used to curb the produciton of the same.
The term "Exhaust Gas Recircultion" is almost self explanatory on its own. Simply put, a part of the exhaust gases are filter and then mixed with the inlet charge(petrol + air) and then sent into the combustion chamber. This results in lesser amount of the air-fuel mixture to be present in the combustion chamber. This results in lowering the combustion temperatures; in turn resulting in lowering of NOx emission.
The diagram here shows an older version of the EGR which works on the amount of vaccum pressure created as the trottle body opens(more you depress the accelarator, more the NOx). On mordern Fuel injected vehicles which have an on board computer to control the amount of air and fuel that should be sent on board, the amount of oxigen both at the inlet and exhaust manifold are continously measured and when NOx is detected at the sensor, EGR is initiated. More the amount of NOx in the exhaust, more the amount of exhaust that gets circulated into the inlet.
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