2.2.5. Jet Fuel (Jet-A and Kerosene) Mechanisms

Four jet fuel reduced mechanisms are available. The flowchart shown in Figure 2.5: Decision flowchart for selecting MFL jet fuel mechanism summarizes the applicability of the four mechanisms. More details of these four mechanisms are presented in the subsections below.

Figure 2.5: Decision flowchart for selecting MFL jet fuel mechanism

Decision flowchart for selecting MFL jet fuel mechanism

 

2.2.5.1. Single-component Jet Fuel

The jetFuel_ndodecane_MFL2017.cks chemistry represents jet fuel with n-dodecane (mechanism name: nc12h26) as the surrogate. The focus of this chemistry set is on modeling combustion at high-temperatures in gas turbines. This chemistry can be used to predict CO, HC (hydrocarbons), and NOx emissions from turbines. The mechanism has been reduced for the following range of conditions:

  1. Pressure: 10–100 bar

  2. Temperature: 1000–2000 K

  3. Equivalence ratio: 0.4–2

  4. EGR: 0–20%

This mechanism has been reduced from the full mechanism “Diesel_PAH_NOx” in the MFL database, which has been thoroughly validated against fundamental experimental data for the operating conditions of interest for gas turbines. The mechanism was reduced from this comprehensive full mechanism using the Reaction Workbench software, for the conditions listed above. A high-temperature kinetics filter was used as a first step for mechanism reduction prior to using other reduction methods in Reaction Workbench.

 

2.2.5.2. Multi-component Jet Fuel

The 4-component jet fuel surrogate has a composition of 36.6/32.2/10.3/20.9 wt% n-dodecane/ heptamethylnonane/ methylcyclohexane / 1,2,4-trimethylbenzene. There are three chemistry sets for this surrogate:

  1. jetFuel_4-comp_MFL2017.cks

  2. jetFuel_4-comp_pseudo-gas-soot_MFL2017.cks

  3. jetFuel_4-comp_detailed-soot_MFL2017.cks

The difference between the three chemistry sets is the soot model they can be used with; they are any acetylene-based empirical soot model, the pseudo-gas soot model, and the Method of Moments soot model, respectively. The same reduced chemistry set may be used for a surrogate whose composition is different, as long as it consists of the same fuel components and includes a similar amount of the fastest-burning component (in this case, n-dodecane). The target application for this chemistry set is modeling combustion at low- to high-temperatures in gas turbines and with soot emissions. It can be used to track soot particle mass, number, and size information in Ansys Chemkin, and using the Method of Moments in Ansys Forte.

For the composition used in the reduction, the surrogate has the following liquid-fuel properties:

Aromatics, vol%18.8
Cetane Number44.4
Molar H/C ratio1.95
Liq. Density, g/cm30.78
Distillation curve
T10, K448
T30, K472
T50, K488
T70, K498
T90, K508

The mechanism has been reduced for the following range of conditions:

  1. Pressure: 10–100 bar

  2. Temperature: 800–2000 K

  3. Equivalence ratio: 0.4–3

  4. EGR: 0–20%.

This mechanism has been reduced from the full mechanism “Diesel_PAH_NOx” in the MFL database, which has been thoroughly validated against fundamental experimental data for the operating conditions of interest for gas turbines. The mechanism was reduced from this comprehensive full mechanism using the Reaction Workbench software, 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. butadiyne (c4h2)

    3. propargyl (c3h3)

    4. benzene (c6h6)

    5. phenyl (c6h5)

    6. toluene (c6h5ch3)

    7. naphthalene (naph)

    8. acenaphthalene (a2r5)

    9. pyrene (a4)

    10. coronene (coronene)

  2. CO (co)

  3. NOx (no and no2)

  4. Unburned hydrocarbons

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

  1. n-Dodecane is nc12h26.

  2. Heptamethylnonane is hmn.

  3. Methylcyclohexane is mch.

  4. 1,2,4-Trimethylbenzene is tmb124.