A Reduced Diesel Surrogate Mechanism for Compression Ignition Engine Applications

Abstract

A skeletal mechanism with 117 species and 472 reactions for a Diesel surrogate i.e., n-heptane, was developed. The detailed mechanism for n-heptane created by Lawrence Livermore National Laboratory (LLNL) was employed as the starting mechanism. The detailed mechanism was then reduced with an enhancement of the Direct Relation Graph (DRG) technique called Parallel DRG-with Error Propagation and Sensitivity Analysis (PDRGEPSA). The reduction was performed for pressures from 20 to 80 atm, equivalence ratios from 0.5 to 2, and an initial temperature range of 600–1200 K, covering the compression ignition (CI) engine conditions. Extensive validations were performed against both 0-D simulations with the detailed mechanism and experimental data for spatially homogeneous systems. In order to perform three-dimensional turbulent spray-combustion and engine simulations, the mechanism was integrated with the multi-zone model in the CONVERGE CFD software to accelerate the calculation of detailed chemical kinetics. The Engine Combustion Network (ECN) data from Sandia National Laboratory was used for validation purposes along with single-cylinder Caterpillar engine data. The skeletal mechanism was able to predict various combustion characteristics accurately such as ignition delay and flame lift-off length (LOL) under different ambient conditions. The performance of the multi-zone solver with respect to the full cell-by-cell chemistry solver (SAGE) is compared for the Caterpillar engine simulation and a good match is obtained with significant speed-up of computational time for the multi-zone solver.