In internal combustion engines, exhaust gas recirculation (EGR) is a nitrogen oxide (NOx) emissions reduction technique used in petrol/gasoline and diesel engines. EGR works by recirculating a portion of an engine's exhaust gas back to the engine cylinders. In a gasoline engine, this inert exhaust displaces the amount of combustible matter in the cylinder. In a diesel engine, the exhaust gas replaces some of the excess oxygen in the pre-combustion mixture. Because NOx forms primarily when a mixture of nitrogen and oxygen is subjected to high temperature, the lower combustion chamber temperatures caused by EGR reduces the amount of NOx the combustion generates. Most modern engines now require exhaust gas recirculation to meet emissions standards.
Read more about Exhaust Gas Recirculation: History, EGR in Spark-ignited Engines, EGR Implementations, In Diesel Engines
Famous quotes containing the words exhaust and/or gas:
“Fear can supplant our real problems only to the extent—unwilling either to assimilate or to exhaust it—we perpetuate it within ourselves like a temptation and enthrone it at the very heart of our solitude.”
—E.M. Cioran (b. 1911)
“Droning a drowsy syncopated tune,
Rocking back and forth to a mellow croon,
I heard a Negro play.
Down on Lenox Avenue the other night
By the pale dull pallor of an old gas light”
—Langston Hughes (1902–1967)