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The Emission Control System:
Exhaust based emissions control:
Exhaust emissions control devices are designed to reduce auto emissions found within the engine exhaust. Most emission devices either recycle gases or clean the gases through further burning or a chemical process. Within this category, we’ll take a look at how the Exhaust Gas Re circulation (EGR) system recycles exhaust to reduce emissions. We’ll also see how the air injection system and catalytic converter work to burn off harmful vapors and gases but in two very different ways.
Exhaust Gas Recirculation (EGR) System
 The exhaust Gas Recirculation system (EGR) was developed as a way to recycle exhaust fumes and prevent the formation of Oxides of Nitrogen (NOx). If you recall from our earlier discussion of NOx, the gas is formed when high temperatures are generated inside the combustion chamber. As hot as the exhaust feels as it exits the tail pipe, it can still lower temperatures during the combustion process.
Here’s how; Engine exhaust is the by product of burning air and fuel in the combustion chamber. During the process, most of the oxygen present in the mixture is burned, consequently engine exhaust tends to contain very low levels of oxygen as it exits the engine. The EGR system recycles oxygen poor exhaust to lower the combustion temperatures. The EGR system recirculates oxygen poor exhaust into the intake manifold where it mixes with fresh air. Exhaust contains less oxygen than air and as a result, when ignited it tends to burn less intensely. chamber. By recalculating exhaust, the engine receives a diluted concentration of oxygen. The diluted mixture does not burn as hot as a more oxygen rich mixture, as a result, NOx emissions are reduced.
 The EGR valve is installed on top of the intake manifold. The valve acts like a gate keeper between the intake and exhaust manifolds. When the engine is cold or idling the valve remains closed. However, when the engine is warm and running at part-throttle, a vacuum acts on the diaphragm, compressing the spring and opening the EGR valve. A metered amount of exhaust is pulled through the bottom of the valve and routed to the intake manifold.
Older EGR valves tended to be vacuum operated. More modern autos rely on a combination of engine vacuum and the engine control module to manage the operation of the EGR valve. |
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Article Pages
1. Emission Control
2. Types Of Pollutants Created By Your Engine
3. 6 Ways In Which Emissions Are Reduced
5. Air Injection And Catalytic Converter
6. Evaporation Emissions Control Systems (EVAP)
7. Positive Crankcase Ventilation (PCV)
8. Automotive Emissions Wrap Up
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