Simulation of nitrogen emissions in a premixed hydrogen flame stabilized on a low swirl burner

Autor: Marcus S. Day, M.J. Lijewski, John B. Bell
Rok vydání: 2013
Předmět:
Zdroj: Proceedings of the Combustion Institute. 34:1173-1182
ISSN: 1540-7489
DOI: 10.1016/j.proci.2012.07.046
Popis: There is considerable interest in developing fuel-flexible, low emissions turbines for power generation. One approach is based on burning a variety of lean premixed fuels with relatively low flame temperatures. Such flames can be stabilized in a low swirl burner configuration, for example, using a variety of fuels such as pure hydrogen and hydrogen-seeded hydrocarbon mixtures. However, many hydrogen-rich fuels are thermodiffusively unstable and burn in cellular flame structures, which can have a significant impact on the local nitrogen chemistry. These cellular burning patterns are characterized by a local enhancement of fuel concentration and a corresponding increase in local flame temperature just downstream. In turn, these regions become sites for enhanced thermal NO x production. The structure of these cells, and their impact on the net emissions of a flame is influenced by the global flame stabilization mechanisms and by local turbulence properties. Here we investigate the role of thermodiffusive instabilities on NO x emissions in the context of a laboratory-scale low swirl burner fueled with a lean hydrogen–air mixture at atmospheric pressure. The simulations show how the cellular burning structures characteristic of lean premixed hydrogen combustion lead to local and global enhancements in the NO x emissions. We quantify the chemical pathways that lead to the formation of NO and N 2 O, and how they are enhanced within local regions of intense burning.
Databáze: OpenAIRE
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