Engines and exhaust after treatment systems for future automotive applications

Abstract

Engine concepts for future automotive applications Safe, clean and efficient engines will become more important in modern societies where we will see higher levels of mobility on one hand and limited resources on the other hand. Gasoline engines for passenger cars have been developed to generate more power and reduce emissions at the same time. Therefore the engine systems have become complex with a number of subsystems. Because of its reliability and efficiency the diesel engine is classically operated in heavy duty vehicles, however in recent years because of its high torque when used with a turbocharger it has become more popular for passenger cars and even sport vehicles as well. The development of the diesel engine especially the direct injection as well as the common rail high pressure injection brought further improvement regarding power, efficiency and emissions. In the future exhaust after treatment systems will be developed in order to comply with emission standards similar to those of gasoline engines. Emission control systems with chemical and physical sensors In order to meet the more and more stringent emission regulations gasoline as well as diesel engines will need continuously improved exhaust after treatment systems. The options for the various applications are highlighted in the following. Today exhaust gas of gasoline engines is typically treated with “Three Way Catalysts” (TWC). The catalyst converts the pollutants CO, NO X and Hydrocarbons into harmless compounds like CO 2, H 2O and N 2 by chemical reactions. Lambda-Sensors control the air fuel ratio of the engine and catalyst performance in order to get the best possible conversion of the pollutants. Modern lean burn engines have other options. Here the pollutants in the exhaust gases are only partially converted by a TWC function i.e. CO and Hydrocarbons. For the remaining NO X a so called NO X Storage Catalyst (NSC) is employed, which chemically stores NO and NO 2 during lean burn phase. For the conversion of stored NO X the engine is periodically shifted to fuel rich operation. This more complex system is controlled with the help of mathematical catalyst models and by Lambda-, Temperature- and optionally NO X -Sensors as well. Diesel engine exhaust of heavy duty vehicles will be treated with ammonia by Selective Catalytic Reduction (SCR) to reduce NO X additionally to the catalytic oxidation of CO and Hydrocarbons. The ammonia is generated on board of the vehicle using harmless precursors like for example urea. For the control of this system Lambda-, Temperature- NO X - and optionally NH 3-Sensors are employed. In addition to gaseous pollutants the particulate emissions from diesel engines will be removed by Diesel Particulate Filters (DPF). The system of oxidation catalyst and DPF is controlled by Temperature-, Pressure- and Particulate-Sensors. The mentioned highlights show that all three goals safe, clean and efficient can be met in the future by both gasoline and diesel engines combined with modern exhaust after treatment systems.