E.3.1. Natural Gas 1-Component Surrogate (Methane) for SI Engine Emissions Predictions

One chemistry set is included for natural gas SI engine applications. This chemistry set, NaturalGas_1comp_ 29sp.cks, consists of 29 species. The mechanism captures the pathways necessary for mid- to high-temperature reactions, and focuses on capturing emissions in combustion for spark-ignited natural-gas engines. Since this mechanism does not include low-temperature reaction pathways, it cannot be used for predicting knocking or for auto-ignition simulations. The mechanism considers the natural gas surrogate as the single-component, methane.

The mechanism is valid for the following conditions:

  1. Equivalence ratios of 0.4-2.

  2. Pressures of 10-100 bar.

  3. Temperatures of ~1000 K and higher.

  4. EGR of 0-20%.

This mechanism has been reduced from the Ansys MFL full GaseousFuels_C0-C6_NOx_MFL2017 mechanism. It has been thoroughly validated against fundamental experimental data for the operating conditions of interest in engines. Validation details are provided in the Ansys Model Fuel Library (MFL) Manual. 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 have been validated as accurate:

  1. CO.

  2. NOx species NO and NO2.

  3. Soot-precursor species acetylene (C2H2).

The species name in the chemistry file for the fuel species methane is ch4.