Parametric analysis of combustion and engine-out emissions in a single cylinder HSDI diesel engine

In-cylinder processes that reduce NOx increase particulates and vice versa. A change in one input variable leads to changes in several output variables. In practice cut and try experiments are still the norm. This research is focused on the experimental in-cylinder investigation of several technological features for understanding the engine out emissions in a demonstrator single cylinder High-Speed Direct-Injection (HSDI) diesel engine equipped with high pressure Common Rail System (CRS). HSDI engines differ from quiescent-chamber, the highly swirling flow, as well as spray/wall and flame/wall interaction effects, can significantly influence the combustion process. Previous research work in diesel combustion modeling has been focused on one injection event and is applicable only to large bore diesel engines. The combustion event in HSDI diesel engine is overcomplicated due to the reduced time frame available to complete the combustion. Previous research work lacks the fuel impingement on the walls of the combustion chamber and the effect of high swirl ratio on combustion and emissions. The new phenomenological model developed in this research accounts for the wall impingement and provides the directional overview of combustion and emissions characterization in a small bore HSDI diesel engine. Trade off emissions maps for advanced HSDI diesel engines equipped with common rail injection systems are non-existent in the literature. Trade-off 2-D and 3-D maps are developed as a part of this research for such an engine, in the conventional combustion and Low Temperature Combustion (LTC) regimes. These maps identified different strategies to reduce engine-out NOx and soot emissions. Applications of the developed 2-D and 3-D maps resulted in identifying OPERAS (Optimum, Pressure, EGR, injection timing Retard, Advance and Swirl ratio) strategies in both conventional and LTC diesel combustion regimes. The engine used in this research is a single-cylinder, 422 c.c., equipped with a common rail injection system, EGR system and swirl control mechanism. The loads and speeds chosen are representative of HEV (Hybrid Electric Vehicle) applications in medium size car.