Exhaust gas recirculation
|
|
Exhaust gas recirculation (EGR) is an efficient NOx (Nitrogen oxide and Nitrogen Dioxide) reduction technique used in most Gasoline and Diesel engines.
EGR works by recirculating a quantity of exhaust gas back to the engine cylinders. Intermixing the recirculated exhaust gas with incoming air reduces the amount of available oxygen to the combustion and lowers the peak temperature of the combustion. This effectively limits the generation of NOx.
Recirculation is usually achieved by piping a route from the exhaust manifold to the inlet manifold. A control valve (EGR Valve) within the circuit regulates and times the gas flow. Some engine designs perform EGR by trapping exhaust gas within the cylinder by not fully expelling it during the exhaust stroke.
In modern diesel engines, the EGR gas is cooled through a heat exchanger to allow the introduction of a greater mass of recirculated gas.
External links
EGR valves (http://www.misterfixit.com/egrvalve.htm)