During the course of, normal vehicle operation, exhaust emission results.
While some of these emissions are harmless, there are other that are, harmful and dangerous.
One way the system reduces these harmful byproducts, is by making the engine, run more efficiently.
The exhaust emission system, also recycles emissions, back through the combustion process or converts them, into harmless gases.
There are basically, three types of systems used to, control exhaust emission:
- Air-injection system.
- Catalytic converter.
- Exhaust gas recirculation (EGR) system.
Typical air-injection system.
In a typical air-injection system, an engine-driven pump, injects air into the exhaust manifold. Next, the air combines with, unburned hydrocarbons and carbon monoxide at a high temperature. And, in effect, continues the combustion process. In this way, a large percentage of the pollutants, that were formerly discharged through the exhaust system are burned. Finally, lowering exhaust emission.
Catalytic converter.
Another area for additional combustion, is the catalytic converter. Consisting of an insulated chamber containing, ceramic pellets or a ceramic honeycomb structure; coated with a thin layer of metals, such as platinum and palladium. As the exhaust gases move through; the metals act as catalysts, to induce the hydrocarbons, carbon monoxide; and nitrogen oxides in the exhaust to convert, to water vapor, carbon dioxide, and nitrogen. Finally, lowering exhaust emission.
Exhaust gas recirculation (EGR) system.
The (EGR) system, allows a precise quantity of exhaust gas, to re-enter the intake system. As a result, effectively changing the chemical makeup, of the air entering the engine. With less oxygen, the now diluted mixture burns slower, lowering temperatures in the combustion chamber by almost 150°C. Consequently, reducing NOx production for a cleaner, more efficient exhaust. Finally, lowering exhaust emission.
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