Date of Award

12-2007

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Mechanical Engineering

Advisor

Miller, Richard S

Committee Member

Beasley , Donald E

Committee Member

Tong , Chenning

Abstract

The effects of Soret and Dufour diffusion on the behavior of high pressure laminar diffusion flames relevant to modern combustion devices are investigated. A novel model for thermal diffusion coefficients is developed based on experimental data found in the literature and the principle of corresponding states. The new model is first compared with existing models and experimental data and is shown to be more accurate and to exhibit correct behavior in the limit of high temperature relevant to combustion. The model furthermore does not exhibit sensitivity to the equation of state, its mixing rules, or unphysical sign changes observed in the prior models. Direct numerical simulations are then conducted for H2/O2, H2/Air, CH4/Air, and C7H16/Air laminar diffusion flames using both detailed and reduced chemical kinetics, accurate property models, and a real gas state equation. Simulations are repeated using the new thermal diffusion factor model, each of the existing models, and purely Fickian/Fourier diffusion in order to both compare the new model's performance as well as to assess its predicted level of cross diffusion influence on the flame evolutions. The new model predicts significant effects of cross diffusion on minor and pollutant species mass fractions for the majority of the flames with significant levels of pressure dependence. The results of the detailed flame simulations are then used to thoroughly document the distributions and statistics of the Lewis number as a function of pressure as a reference for future modeling efforts.

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