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Reduced kinetic mechanisms for modelling LPP combustión in gas turbines

E.T.S.I. Aeronáuticos (UPM)
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  • Física
  • Aeronáutica
  • Chemistry


12-1 Reduced Kinetic Mechanisms for Modelling LPP Combustión in Gas Turbines A. Liñán, M. Bollig Universidad Politécnica de Madrid Pza. Cardenal Cisneros 3, 28040 Madrid, Spain. A. L. Sánchez Universidad Carlos III Butarque 15, 28911 Leganés, Spain. B. Lázaro SENER Severo Ochoa 4, 28760 Tres Cantos, Spain. 1. SUMMARY Lean premixed methane-air flames are investigated in an effort to facilítate the numerical description of CO and NO emissions in LPP (lean premixed prevaporized) combustión systems. Starting with a detailed chemistry description that includes 195 elementary steps, sensiüvity procedures and steady-state approximations are introduced to obtain two different four-step reduced mechanisms, which employ either H or OH as the intermedíate representing the radical-pool evolution. The resulting reduced mechanisms are especially well suited to describe high-pressure, lean premixed combustión. Based on the resulting flame structures, and following previous analyses, the mechanism is further simplified to give a two-step description, in which fuel is consumed and CO is produced according to the fast overall step CH4+3/2 02->CO+2H20 , while CO is slowly oxidized according to the overall step CO+l/202—>C02. Because of its associated fast rate, fuel consumption takes place in thin layers, while CO oxidation occurs downstream in a distributed marmer, in a región where CO is the only intermedíate not in steady state. In this two-step description, the rate of fuel consumption is assigned a heuristic Arrhenius dependence that adequately reproduces laminar burning velocities, whereas the rate of CO oxidation is extracted from a reduced chemistry analysis. Preliminar/ results corresponding to one- dimensional unstrained flames indícate that the formulation reproduces well flame structures, including profiles of CO, temperature and radicáis. The accuracy of the resulting profiles suggests that the proposed formulation can also be used to calcúlate

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