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:
“Language is like soil. However rich, it is subject to erosion, and its fertility is constantly threatened by uses that exhaust its vitality. It needs constant re-invigoration if it is not to become arid and sterile.”
—Elizabeth Drew (1887–1965)
“... when I awake in the middle of the night, since I knew not where I was, I did not even know at first who I was; I only had in the first simplicity the feeling of existing as it must quiver in an animal.... I spent one second above the centuries of civilization, and the confused glimpse of the gas lamps, then of the shirts with turned-down collars, recomposed, little by little, the original lines of my self.”
—Marcel Proust (1871–1922)