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HyChem (Hybrid Chemistry) is an approach to modeling the combustion chemistry of real liquid fuels. The approach takes advantage of the key physics underlying the high-temperature combustion of large hydrocarbon fuels [1,2]:
1. Pyrolysis/oxidative pyrolysis of the fuel occurs first followed by oxidation of the pyrolysis products;
2. The oxidation of the pyrolysis products is rate limiting in the overal fuel oxidation process;
3. The combustion of the multicomponent fuel follows the principle of large fuel components [3].
The approach combines experimentally constrained, lumped reaction steps for fuel pyrolysis and oxidative pyrolysis with detailed reaction model for the pyrolysis and oxidation of the fuel pyrolysis products. For conventional petroleum-derived fuels, the pyrolysis products considered are usually ethylene (C2H4), hydrogen (H2), methane (CH4), propene (C3H6), iso-butene (i-C4H8), 1-butene (1-C4H8), benzene (C6H6), tuluene (C7H8), and usually two radical species (CH3 and H). Other species can be added as needed, depending on the fuel composition. For example, the pyrolysis products of some synthetic fuels can vary with respect to the composition and molecular structure of the parent fuel. In the current release of the HyChem models, the reaction kinetics of the pyrolysis products is described by USC Mech II [4]. Details of the HyChem approach and procedures can be found in [1,2] and also on the Approach page.
HyChem model releases
HyChem models have been developed for a substantial number of aviation fuels as listed in the table below. Skeletal and reduced models are also available CFD applications. The effort is the result of close collaboration among Stanford University, University of Southern California, University of Illinois at Chicago, and University of Connecticut.
List of aviation and rocket fuels for which models are available (View key fuel properties by clicking on the fuel name).
| Fuel* | POSF number** | Type & Applications |
| A1 | 10264 | JP-8, Distillate jet fuel |
| A2 | 10325 | Jet A, Distillate jet fuel |
| A3 | 10289 | JP-5, Distillate jet fuel |
| JP-10 | N/A | JP-10, Synthetic jet fuel |
| RP2-1 | 7688 | Distillate rocket fuel |
| RP2-2 | 5433 | Distillate rocket fuel |
| Shell A | N/A | Gasoline fuel |
| Shell D | N/A | Gasoline fuel |
| C1 | 11498 | Gevo ATJ, Synthetic jet fuel |
| C5 | 12345 | Synthetic jet fuel |
* A1-A3, C1, and C5 are fuel designations by the National Jet Fuels Combustion Program (NJFCP). See ref. [5].
** The POSF number has no particular significance other than a batch number in the
fuel repository where the fuel was acquired.
Acknowledgements
The work was funded by the Air Force Office of Scientific Research (AFOSR) under the technical supervision of Dr. Chiping Li. The work was also supported by the National Aeronautics and Space Administration (NASA) , the Federal Aviation Administration (FAA), and Shell Global Solutions.
References
[1] H. Wang, R. Xu, K. Wang, C.T. Bowman, D.F. Davidson, R.K. Hanson, K. Brezinsky, F.N. Egolfopoulos, A physics-based approach to modeling real-fuel combustion chemistry - I. Evidence from experiments, and thermodynamic, chemical kinetic and statistical considerations, Combustion and Flame 193 (2018) 502-519.
[2] R. Xu, K. Wang, S. Banerjee, J. Shao, T. Parise, Y. Zhu, S. Wang, A. Movaghar, D.J. Lee, R. Zhao, X. Han, Y. Gao, T. Lu, K. Brezinsky, F.N. Egolfopoulos, D.F. Davidson, R.K. Hanson, C.T. Bowman, H. Wang, A physics-based approach to modeling real-fuel combustion chemistry - II. Reaction kinetic models of jet and rocket fuels, Combustion and Flame 193 (2018) 520-537.
[3] R. Xu, H. Wang, Principle of large component number in multicomponent fuel combustion – a Monte Carlo study, Proceedings of the Combustion Institute 37 (2019) 613-620.
[4] H. Wang, X. You, A.V. Joshi, S.G. Davis, A. Laskin, F. Egolfopoulos, C.K. Law, USC Mech Version II. High-Temperature Combustion Reaction Model of H2/CO/C1-C4 Compounds. http://ignis.usc.edu/Mechanisms/USC-Mech II/USC_Mech II.htm, 2007.
[5] M. Colket, J. Heyne, M. Rumizen, M. Gupta, T. Edwards, W.M. Roquemore, G. Andac, R. Boehm, J. Lovett, R. Williams, Overview of the National Jet Fuels Combustion Program, AIAA Journal 55 (2017) 1087-1104.