Pdf calculations of turbulent lifted flames of H 2 /N 2 fuel issuing into a vitiated co-flow
2004; Taylor & Francis; Volume: 8; Issue: 1 Linguagem: Inglês
10.1088/1364-7830/8/1/001
ISSN1741-3559
AutoresAssaad R. Masri, Ruike Cao, Stephen B. Pope, Graham Goldin,
Tópico(s)Combustion and Detonation Processes
ResumoAbstract This paper presents detailed calculations of the flow, mixing and composition fields of a simple jet of hydrogen–nitrogen mixture issuing into a vitiated co-flowing stream. The co-flow contains oxygen as well as combustion products and is sufficiently hot to provide an ignition source for a flame that stabilizes at some ten diameters downstream of the jet exit plane. This configuration forms a good model problem for studying lifted flames as well as issues of auto-ignition. The calculations employ a composition probability density function (PDF) approach coupled to the commercial CFD package FLUENT. The in situ adaptive tabulation method is adopted to account for detailed chemical kinetics. A simple k–ε model is used for turbulence along with a low Reynolds number model for the walls. Calculations are optimized to obtain a numerically accurate solution and are repeated for two different H2 mechanisms, each consisting of ten species. The flame is found to be largely controlled by chemical rather than mixing processes. The mechanisms used yield different lift-off heights and compositions that straddle the data. Ignition delays are found to be extremely sensitive to the chemical kinetic rates of some reactions in the mechanisms.
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