### Abstract

Radiative heat transfer is studied numerically for high-pressure laminar H_{2}–air jet diffusion flames, with pressure ranging from 1 to 30 bar. Water vapour is assumed to be the only radiatively participating species. Two different radiation models are employed, the first being the full spectrum k-distribution model together with conventional Radiative Transfer Equation (RTE) solvers. Narrowband k-distributions of water vapour are calculated and databased from the HITEMP 2010 database, which claims to retain accuracy up to 4000 K. The full-spectrum k-distributions are assembled from their narrowband counterparts to yield high accuracy with little additional computational cost. The RTE is solved using various spherical harmonics methods, such as P_{1}, simplified P_{3} (SP_{3}) and simplified P_{5} (SP_{5}). The resulting partial differential equations as well as other transport equations in the laminar diffusion flames are discretized with the finite-volume method in OpenFOAM^{®}. The second radiation model is a Photon Monte Carlo (PMC) method coupled with a line-by-line spectral model. The PMC absorption coefficient database is derived from the same spectroscopy database as the k-distribution methods. A time blending scheme is used to reduce PMC calculations at each time step. Differential diffusion effects, which are important in laminar hydrogen flames, are also included in the scalar transport equations. It was found that the optically thin approximation overpredicts radiative heat loss at elevated pressures. Peak flame temperature is less affected by radiation because of faster chemical reactions at high pressures. Significant cooling effects are observed at downstream locations. As pressure increases, the performance of RTE models starts to deviate due to increased optical thickness. SP_{N} models perform only marginally better than P_{1} because P_{1} is adequate except at very high pressure.

Original language | English (US) |
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Pages (from-to) | 607-626 |

Number of pages | 20 |

Journal | Combustion Theory and Modelling |

Volume | 18 |

Issue number | 6 |

DOIs | |

State | Published - Nov 2 2014 |

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### All Science Journal Classification (ASJC) codes

- Chemistry(all)
- Chemical Engineering(all)
- Modeling and Simulation
- Fuel Technology
- Energy Engineering and Power Technology
- Physics and Astronomy(all)

### Cite this

*Combustion Theory and Modelling*,

*18*(6), 607-626. https://doi.org/10.1080/13647830.2014.959060