NOx-Reduction for Diesel Combustion Processes by means of High Energetic Air Guided Mixture Formation

Authors

Dr.-Ing. P. Kreuter, Dr.-Ing. P. Heuser, Dr.-Ing. M. Wensing, Dipl.-Ing. R. Bey, Dr.-Ing. C. Fettes, Dipl.-Ing. J. Baltes, Dipl.-Ing. W. Cosler, Meta Motoren- und Energie-Technik GmbH, Herzogenrath

Year

2004

Print Info

Fortschritt-Berichte VDI, Reihe 12, Nr. 566

Summary

The main targets concerning Diesel engine development are defined by the future exhaust gas legislation (EURO IV, EURO V, same standards for SI and Diesel engines in USA). Due to technical reasons, the conflict between NOx-emissions and soot emissions still exists even when particulate filters are applied. This conflict is caused by the diesel process with its inhomogeneous mixture formation. Due to the direct injection of fuel into the combustion bowl, locally rich regions (soot formation) and local regions with an air/fuel ratio (AFR) around 16 (NOx formation) co-exist. Former applications using prechamber engines could avoid regions around AFR = 16. The mixture formation was significantly increased using the gas flow by means of the energy generated in the prechamber. The control of mixture formation and combustion using modern Diesel engines mainly is dominated by the injection systems. Currently, the swirl energy is not exactly controllable and therefore is a compromise concerning the engine operation map. This paper describes the application of impulse charging to control mixture formation and combustion for Diesel engines. The freely controllable electromagnetic system is positioned in front of the inlet valves of the engine. For the Diesel engine a common system for filling and swirl port was applied to each engine cylinder. Keeping the impulse charger module closed during the intake stroke, a vacuum is generated by means of the downmoving piston. After the opening of the impulse charger, this vacuum is transferred into a higher flow velocity and – in combination with the port design – into a higher swirl energy. The swirl energy used for the mixture formation is adjustable by shifting the timing of the impulse charger opening. Results prove the effect of the impulse charger on Diesel-specific mixture formation, combustion and emissions. In single operation points a reduction of raw emissions of more than 60% (NOx) is observable. Simultaneously, the soot emissions can be reduced. Furthermore, the application of the impulse charger especially can improve the engine start-behaviour.

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