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Development of Future Engines Using Combustion Diagnostics, Computational Fluid Dynamics, and Advanced Optical Diagnostics
Published October 22, 2006 by Society of Automotive Engineers of Japan in Japan
A global renaissance in advancements of automotive propulsion system technology and resulting portfolio complexity is in full swing. Significant complexity is being driven by the "march to zero" in noxious emissions and our drive towards the upper limit of thermodynamic efficiency. General Motors Corporation is attacking this challenge with a three-pronged technical strategy which encompasses improved gasoline and diesel engines, hybridization and hydrogen fuel cell vehicles. This has resulted in an exponential increase in the research and development requirements to support this portfolio. Key development tools, namely combustion diagnostics, computational fluid dynamics (CFD) and optical diagnostics, play a critical role in the successful development of our current and future portfolio and are applied synergistically. The focus in this paper is on application examples of these tools to develop two of the most promising gasoline-engine technologies, namely spray-guided spark ignition direct injection (SG-SIDI) and homogeneous charge compression ignition (HCCI). Stratified combustion in SG-SIDI engines has been investigated using detailed CFD modelling and high-speed imaging, cylinder pressure analysis and spark spectroscopy. This has led to fundamental understanding of the complex interaction of the fuel spray with the spark plug as well as the bulk mixture preparation and combustion. HCCI concepts, while also requiring the fluid dynamics to be treated accurately, place a premium on the detailed chemistry and ultimately require a fully-coupled zonal approach for simulation. We have combined optical and combustion diagnostics to successfully develop stratified ignition strategies for low-load HCCI. The interplay and combination of combustion and advanced optical diagnostics with CFD allows fundamental, quantitative understanding of in-cylinder processes to be distilled for the key technologies of future engines.