Exhaust gas recirculation
In internal combustion engines, exhaust gas recirculation (EGR) is a nitrogen oxide (NOx) emissions reduction technique used in petrol/gasoline, diesel engines and some hydrogen engines. EGR works by recirculating a portion of an engine's exhaust gas back to the engine cylinders. The exhaust gas displaces atmospheric air and reduces O2 in the combustion chamber. Reducing the amount of oxygen reduces the amount of fuel that can burn in the cylinder thereby reducing peak in-cylinder temperatures. The actual amount of recirculated exhaust gas varies with the engine operating parameters.
EGR valve the top of box on top of the inlet manifold of a Saab H engine in a 1987 Saab 90
Electronically actuated EGR Valve for VW BMN engine
The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is called a compression-ignition engine. This contrasts with engines using spark plug-ignition of the air-fuel mixture, such as a petrol engine or a gas engine.
Diesel engine built by Langen & Wolf under licence, 1898
Rudolf Diesel's 1893 patent on a rational heat motor
Diesel's second prototype. It is a modification of the first experimental engine. On 17 February 1894, this engine ran under its own power for the first time. Effective efficiency 16.6% Fuel consumption 519 g·kW−1·h−1
First fully functional diesel engine, designed by Imanuel Lauster, built from scratch, and finished by October 1896. Rated power 13.1 kW Effective efficiency 26.2% Fuel consumption 324 g·kW−1·h−1.