What Is The Role Of EGR?

release time:2020-06-15 09:53Views:Times
The EGR valve is a mechatronic product installed on the diesel engine to control the amount of exhaust gas recirculation fed back to the intake system. 
 
It is usually located on the right side of the intake manifold, near the throttle body, and has a short metal pipe leading to the exhaust manifold connected to it. Its role is to control the amount of exhaust gas entering the intake manifold, so that a certain amount of exhaust gas flows into the intake manifold for recirculation.
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The EGR valve is used to reduce the emission of nitrogen oxides (NOX) in the exhaust gas. Nitrogen and oxygen will only undergo chemical reaction under high temperature and high pressure conditions. The temperature and pressure in the engine combustion chamber meet the above conditions, especially during forced acceleration.  

When the engine is running under load, the EGR valve opens, allowing a small amount of exhaust gas to enter the intake manifold and enter the combustion chamber together with the combustible mixture. At idle, the EGR valve is closed and almost no exhaust gas is recirculated to the engine.

Automobile exhaust gas is a non-combustible gas (without fuel and oxidant) and does not participate in combustion in the combustion chamber. It reduces the combustion temperature and pressure by absorbing part of the heat generated by combustion to reduce the amount of nitrogen oxide generated. 

The amount of exhaust gas entering the combustion chamber increases as the engine speed and load increase.

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Exhaust gas recirculation is a method of introducing part of the exhaust gas to the fresh air (or mixed gas) that is sucked into the cylinder and recirculating it to participate in the combustion during the operation of the engine. Its role is to reduce NOx emissions. 

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Picture is from https://www.researchgate.net/figure/A-schematic-diagram-of-EGR-system_fig1_49619470
 
 
 
NOx is a gas that is extremely harmful to the human body, which is mainly produced under the condition of high temperature and oxygen enrichment. During the engine working process, if part of the exhaust gas is reintroduced into the cylinder at the right time and in an appropriate amount, because the main component of the exhaust gas, CO2, has a larger specific heat capacity, the exhaust gas can absorb part of the heat generated by the combustion and take it out of the cylinder. A certain dilution effect, thus reducing the maximum temperature and oxygen content of the engine combustion, thereby reducing the amount of NOx compounds produced.
 

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