HCCI engine CFD simulations: Influence of intake temperature, cylinder wall temperature and the equivalence ratio on ignition timing

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The Ohio State University

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To meet the increasingly stringent emission standards, the automotive industry is actively searching for means to improve the efficiency of an internal combustion engine. One promising solution is a homogeneous charge compression ignition (HCCI) engine which has shown potential in achieving high fuel efficiency while maintaining low emission. However, there remain several challenges to commercialize the HCCI engine due to the nature of its working principle. Since the HCCI engine relies purely on compression to achieve ignition, controlling the ignition timing is much harder than in spark-ignition (SI) engines and diesel engines. This study focuses on simulating the ignition and combustion processes inside the HCCI engines and investigating the impacts of different operating conditions, such as intake temperature, the equivalence ratio, and cylinder wall temperature. The study is conducted by using the CONVERGE Computational Fluid Dynamics (CFD) software which allows robust and accurate engine simulation. Current progress shows that lower intake temperature retards the combustion timing and decreases combustion efficiency. Results from CFD simulations are compared to experimental data for a research HCCI engine. Trends observed in the simulations show good agreement with those in the experiments in terms of the impact of different intake temperatures. Further investigation shows that lower cylinder wall temperature retards ignition timing and extends ignition duration. The mixture temperature is found to be more sensitive to the cylinder wall temperature than the intake temperature. When lean mixtures with the equivalence ratio smaller than 1 are considered, the ignition of iso-octane is advanced as it’s equivalence ratio increases.



CFD, Engine simulation, intake temperature, cylinder wall temperature, equivalence ratio, combustion phasing