This study aims to model partially premixed combustion (PPC) with flame index concept for low-octane gasoline in compression ignition (CI) engine. The validation experiment was carried out in a full-transparent AVL single optical CI engine. Fuel injection timing was fixed at -30 CAD aTDC to achieve PPC operation condition. Primary reference fuel, PRF77, with octane number of 77, was selected as test low-octane gasoline surrogate fuel. Multiple optical diagnostics were performed to validate numerical simulations, including high-speed color imaging and spray-tracer planar laser-induced fluorescence (PLIF) imaging. Full cycle engine simulations were performed using a CFD code CONVERGETM. The Takeno flame index was used to analyze the evolution of premixed and non-premixed flames. The simulation results show that the flame index could be used as a useful indicator for evaluating and quantifying combustion development under PPC operating condition. Premixed flames distribution is more consistent with the relatively low-temperature contour of 1500 K, most of the fuel/air mixture is burned out and less premixed flames exits at higher temperature contour of 2300 K.
|Title of host publication
|12th Asia-Pacific Conference on Combustion, ASPACC 2019
|Published - Jan 1 2019