Add a big nonreacting mechanism for POSF fuels (#626)

* Add fuellib_posf_nonreacting mechanism

* Delete Mechanisms/fuellib_posf_nonreacting/~$ref-compounds.xlsx

* add sprayProps files

* update README

* Update README and comment in mechanism files

* Clean up odds-n-ends

Author: d-montgomery

Mechanisms/fuellib_posf_nonreacting/LJ-WellDepth.py

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+# Given Epsilon in J/mol, calculate the Lennard-Jones well depth in Kelvin.
+
+# Epsilon in J/mol
+epsilon = 4954.04
+
+def epsilon_to_lj_welldepth(epsilon_j_per_mol):
+    """Convert Lennard-Jones epsilon from J/mol to K."""
+    kb = 1.380649e-23  # Boltzmann constant in J/K
+    Na = 6.02214076e23  # Avogadro's number in 1/mol
+    epsilon_per_molecule = epsilon_j_per_mol / Na
+    lj_welldepth = epsilon_per_molecule / kb
+    print(f"Lennard-Jones well depth: {lj_welldepth:.3f} K") 
+
+epsilon_to_lj_welldepth(epsilon)

Mechanisms/fuellib_posf_nonreacting/Make.package

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+CEXE_headers+=mechanism.H
+
+CEXE_sources+=mechanism.cpp

Mechanisms/fuellib_posf_nonreacting/README.md

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+# FuelLib POSF Non-Reacting Mechanism
+This 93 species mechanism is designed to be used with the POSF fuels available in [FuelLib](https://github.com/nrel/fuellib). It provides thermo and transport data for the specific reference compounds (see ref-compounds.csv) selected for each GCxGC bin.
+
+The files included in `spray_input_files` are are generated using FuelLib's `Export4Pele.py` script: 
+
+~~~
+cd $FUELLIB_DIR/source
+python Export4Pele.py --fuel_name posf10264 
+python Export4Pele.py --fuel_name posf10264 --liq_prop_model mp
+~~~
+
+More information about generating these input files can be found in [FuelLib's documentation](https://nrel.github.io/FuelLib/tutorials-export4pele.html). Note that the units in these files are in MKS as is required for PeleLMeX. Similar files can be created for PeleC using the option `--units cgs` in the `Export4Pele.py` script. As of 10/2025, PeleC only supports the MP liquid property model. Below is an example of how to generate the required input file for use with PeleC:
+
+~~~
+cd $FUELLIB_DIR/source
+python Export4Pele.py --fuel_name posf10264 --units cgs --liq_prop_model mp
+~~~
+

Mechanisms/fuellib_posf_nonreacting/convert.sh

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+#!/usr/bin/env bash
+
+MECH_HOME="$(pwd)"
+MECH_FILE="${MECH_HOME}/mechanism.yaml"
+bash ../converter.sh -f "${MECH_FILE}"