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Direct-injection spark-ignition (DISI) engine became an important initiative of future SI engines due to its potential for the enhanced fuel economy and transient response. The uniqueness of DISI engines is its operation in stratified mode during low loads and idling by injecting small amount of fuel in a limited region within the combustion chamber to achieve a combustible mixture and a ultra-lean mixture elsewhere. Two major combustion systems have been introduced, so far, to achieve the stratification; wide spacing and close spacing systems.
In the wide spacing system, the fuel impinges on the piston cavity that guides the post-impinged spray towards the spark plug with the assistance of the airflow pattern. In the close spacing system, otherwise known as the spray guided system, a compact spray is injected close to the spark plug location. In this case, the spray geometry should not vary significantly with airflow speed so as to avoid engine misfire.
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Until now, the research in KAIST Engine lab has been focused on the optimization of wall-guided systems. The previous research scopes in KAIST are summarized as follows;
- The analysis of macroscopic and microscopic spray development at different injector operating conditions using laser optics and microscopic imaging systems
- The analysis of combustion characteristics under varied operating and surrounding conditions, such as injection pressure, fuel temperature and air flow by visualizing flame and radicals
- The application of combustion improvement technology, such as split injection and EGR
However, the trend in DISI engine is changing from wall-guided combustion system to spray-guided combustion system for the realization of more efficient and clean DISI engines.
Therefore, we are now preparing the experimental setup for spray-guided combustion system.
Spray Guided DISI Engine with SIEMENS Piezo Injector, BMW N57 ENgine (BMW 335i)
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