Technical Paper
Analysis of Thermal Stratification Effects in HCCI Engines Using Large Eddy Simulations and Detailed Chemical Kinetics
2018-04-03
2018-01-0189
The operating range of Homogeneous Charge Compression Ignition (HCCI) engines is limited to low and medium loads by high heat release rates. Negative Valve Overlap (NVO) can be used to facilitate ignition of high octane number fuels and control pressure rise rates by diluting the mixture with hot residual gas and introducing some thermal stratification. Controlling the thermal stratification results in sequential autoignition, reduced heat release rates, and operating range extension. Therefore, fundamental understanding of thermal stratification in HCCI combustion with high levels of internal residuals is necessary, along with the development of appropriate models to simulate thermal stratification and its effects on HCCI combustion. A 3-D Computational Fluid Dynamics (CFD) model of a 2.0 L GM Ecotec engine (LNF type) engine cylinder, modified for HCCI combustion, was developed using CONVERGE CFD.