Emission Reduction during Cold Start by Combustion Controlled Increase of In-Cylinder Temperatures 2018-01-1740

A significant share of the emissions of a vehicle with internal combustion engine originates from the cold start. In addition to the more stringent limits for particulate emissions due the introduction of the Euro 6c standard for gasoline engines with direct injection (GDI), exhaust gas emission testing is currently performed applying the real driving emission test procedure (RDE) required by the Euro 6d TEMP standard. The RDE test procedure is not clearly defined, potentially allowing high loads immediately after the engine start. Under such circumstances the combustion chamber features low surface temperatures impairing emission performance and in particular provoking the excessive generation of hydrocarbon and particulate emissions. It is therefore important not only to examine the heating of the catalytic converter during the cold start, but also the preconditioning of the combustion chamber itself.

This paper describes the influence of different catalytic converter heating strategies on the emissions during heating operation, as well as during the subsequent load demand. Furthermore, the influence of the engine temperature at engine start is investigated. In addition to a stoichiometric and a lean heating operation strategy another combustion process strategy is presented. The novel strategy provides heating of the combustion chamber, without decreasing the catalyst converter heating significantly. The studies were carried out on a 2.0 liter gasoline engine with direct injection (SIDI) on an engine test bench. Both gaseous emissions and particulate emissions were monitored. Furthermore, the origins of particulate emissions were examined in more detail by means of high-speed camera recordings of the soot radiation inside the combustion chamber. To assess the flame propagation, high-speed camera footage was combined with the signals from a fiber optical sparkplug (FOSP).