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Interaction between a diesel spray and piston plays a significant role in overall combustion and emissions performance in compression-ignition engines. It is essential to design the lip feature respective to spray targeting and the following charge motion for combustion systems that rely on spray-piston interaction strongly, such as a stepped-lip piston. This study used a numerical campaign using computational fluid dynamics (CFD) simulation to optimize a stepped-lip combustion system at a 22:1 compression ratio (CR) for both performance and emissions. This is a substantial step up in CR from the stock value of 17:1 for the same engine platform. A machine learning model was used to identify the best combination of features from a design space involving hundreds of potential piston designs and injector nozzle configurations. This study provides a discussion on the general combustion characteristics of the stepped-lip combustion system and the sensitivity of the design parameters.

As the efforts to push capabilities of current engine hardware to their durability limits increases, more accurate and reliable analysis is necessary to ensure that designs are robust. This paper evaluates a method of Conjugate Heat Transfer (CHT) analysis for a gasoline and a diesel engine that combines combustion Computational Fluid Dynamics (CFD), engine Finite Element Analysis (FEA), and cooling jacket CFD with the goal of obtaining more accurate temperature distribution and heat loss predictions in an engine compared to standard de-coupled CFD and FEA analysis methods. This novel CHT technique was successfully applied to a 2.5 liter GM LHU gasoline engine at 3000 rpm and a 15.0 liter Cummins ISX heavy duty diesel engine operating at 1250 rpm. Combustion CFD simulations results for the gasoline and diesel engines are validated with the experimental data for cylinder pressure and heat release rate.

As the design of engines advances and continues to push the capabilities of current hardware closer to their durability limits, more accurate and reliable analysis is necessary to ensure that designs are robust. This research evaluates a method of conjugate heat transfer analysis for a diesel engine that combines the combustion CFD, Engine FEA, and cooling jacket CFD with the aim of getting more accurate heat loss predictions and a more accurate temperature distribution in the engine than with current analysis methods. A 15.0 L Cummins ISX heavy duty engine operating at 1250 RPM and 15 bar BMEP load is selected for this work. Spray combustion computational fluid dynamics (CFD) simulations are performed for the diesel engine and the results are validated with experimental data. Finite Element Analysis (FEA) simulations were performed in a separate software platform.