Gasoline Combustion Modeling of Direct and Port-Fuel Injected Engines using a Reduced Chemical Mechanism 2013-01-1098

A set of reduced chemical mechanisms was developed for use in multi-dimensional engine simulations of premixed gasoline combustion. The detailed Primary Reference Fuel (PRF) mechanism (1034 species, 4236 reactions) from Lawrence Livermore National Laboratory (LLNL) was employed as the starting mechanism. The detailed mechanism, referred to here as LLNL-PRF, was reduced using a technique known as Parallel Direct Relation Graph with Error Propagation and Sensitivity Analysis. This technique allows for efficient mechanism reduction by parallelizing the ignition delay calculations used in the reduction process. The reduction was performed for a temperature range of 800 to 1500 K and equivalence ratios of 0.5 to 1.5. The pressure range of interest was 0.75 bar to 40 bar, as dictated by the wide range in spark timing cylinder pressures for the various cases. In order to keep the mechanisms relatively small, two reductions were performed. The first mechanism, referred to here as HIGHP (123 reactions, 502 reactions), was reduced under a pressure range of 20-50 bar. The second mechanism, referred to here as LOWP (110 species, 488 reactions), was reduced for a pressure range of 2-10 bar.

The reduced mechanisms were coupled with Adaptive Mesh Refinement (AMR), a multi-zone chemistry solver, and a RANS turbulence model to predict premixed gasoline combustion under a wide range of engine conditions. First, a Turbo-charged Direct Injection (TCDI) engine was simulated for a variety of engine speeds, engine loads and displacements. Next a Port-Fuel Injected (PFI) engine with a Charge Motion Control Valve (CMCV) was simulated under a range of valve lift profiles, spark timings, and control valve geometries. Reasonable agreement with the available experimental data was achieved for both the DI and PFI cases