E.1.2. n-Heptane-Methane Model for Simulations of Compression-Ignition Diesel and Natural-Gas–Diesel Fueled Engines

The Diesel-naturalGas_2comp_137sp.cks chemistry set consists of 137 species. It represents diesel fuel with a single-component surrogate: n-heptane. The mechanism captures the pathways necessary for both high-temperature and low-temperature reactions, including the intermediate negative-temperature-coefficient (NTC) regime, and therefore can be used for accurately modeling autoignition behavior and emissions for any diesel engine. In addition to n-heptane, it also retains kinetics for methane as a single-component surrogate for natural gas. Therefore, the mechanism can also be used for a dual fuel engine running on natural gas with diesel pilot.

The mechanism has been validated against fundamental data for the following conditions:

  1. Equivalence ratios of 0.5-3.

  2. Pressures of 1-150 bar.

  3. Temperatures of ~650 K and higher.

  4. EGR of 0-50%.

This mechanism has been reduced from the Gasoline_PAH_NOx mechanism from the Ansys MFL that consists of more than 2500 species. As documented in the MFL Manual, which has been thoroughly validated against fundamental experimental data for the operating conditions of interest in engines. The mechanism was reduced from this comprehensive "full" mechanism using Ansys Chemkin Reaction Workbench software [32], for the conditions listed above.

For the emissions, the following species predictions are expected to be accurately predicted:

  1. CO.

  2. NOx species NO and NO2.

  3. Soot-precursor species acetylene (C2H2).

The species names in the chemistry file: for the n-heptane fuel species is nc7h16; for the methane fuel species is ch4.