Experimental Investigation on Catalyst-Heating Strategies and Potential of GDI Combustion Systems

Beside the fuel consumption reduction the emission reduction is one of the main development objectives. The oncoming increasingly stringent emission limits demand improvements to the emission level especially in the cold start and engine warm-up phase when the catalyst is still inactivate. In this phase it is necessary to produce raw emissions on a very low level and to reach the catalyst light-off temperature as fast as possible using a suitable injection strategy.

In this paper the potentials and risks of injection strategies for efficient catalyst heating (lean warm-up without secondary-air pump) with piezo and solenoid GDI combustion systems, in side and central mounting position, are introduced. The main emphasis is to obtain low HC emissions and high exhaust heat flow with acceptable engine smoothness by deriving suitable tuning parameters. During the investigations the various degrees of freedom of the applied GDI Engine were used in the best possible way.

The basic investigations were carried out with steady state single cylinder engine dyno tests and cold engine conditions. For a deeper understanding of the in-cylinder processes, such as spray penetration and soot formation, an optical measurement technique based on high-speed video-endoscopy was used. It is shown that the Piezo and Solenoid GDI Combustion Systems of the Continental Automotive GmbH have the potential to perform a highly efficient catalyst heating engine operation, by means of suitable double and triple injection strategies.