E.2.2. TRF-Ethanol Model for Spark-Ignition Simulations for Non-knocking Conditions, Focus on Soot Particle Tracking

The Gasoline_4comp_171sp__soot-particle-tracking.cks chemistry set consists of a 171-species gas-phase mechanism, and a soot surface mechanism. The focus of this chemistry set is on accurate soot modeling from combustion in spark-ignited engines. This chemistry set can be used to track soot particle using the Method of Moments in Ansys Forte.

The soot surface mechanism includes:

  1. Soot nucleation pathways through multiple pathways.

  2. HACA- and PAH-based soot growth pathways.

  3. Soot oxidation through O2 and OH.

This mechanism represents gasoline-ethanol with the 4-component n-heptane/iso-octane / toluene/ethanol as the fuel surrogate. The mechanism captures the pathways necessary for only the high-temperature reactions. Since this mechanism does not include low-temperature reaction pathways, it cannot be used for predicting knocking.

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

  1. Equivalence ratios of 0.4-3. This range is to capture both GDI and port-fuel injection engine local environments.

  2. Pressures of 1-100 bar.

  3. High-temperatures of ~1200 K and higher.

  4. EGR of 0-40%.

  5. Octane numbers of ~85-100. The composition used for mechanism reduction had a composition of 39/30/21/10 wt% toluene/iso-octane/n-heptane /ethanol. n-Heptane and iso-octane compositions can be modified to change the octane number within the range listed above.

This mechanism has been reduced from a larger gasoline kinetics mechanism consisting of ~2600 species, which has been thoroughly validated against fundamental experimental data for the operating conditions of interest in engines, under the Model Fuels Consortium [20]. The Ansys Model Fuel Library (MFL) Manual includes the mechanism validation plots. The mechanism was reduced from this comprehensive "full" mechanism using the Ansys Chemkin Reaction Workbench software [31], for the conditions listed above.

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

  1. Soot-precursor species:

    1. acetylene (c2h2).

    2. propargyl (c3h3).

    3. benzene (c6h6).

    4. phenyl (c6h5).

    5. toluene (c6h5ch3).

    6. naphthalene (naph).

    7. acenaphthalene (a2r5).

    8. pyrene (a4).

    9. coronene (coronene).

  2. CO.

  3. NOx species NO and NO2.

The species names in the chemistry file for the fuel species are:

  1. iso-Octane is ic8h18.

  2. n-Heptane is nc7h16.

  3. Toluene is c6h5ch3.

  4. Ethanol is c2h5oh.