Impinging Flames

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Laboratory of Thermofluids, Combustion
       and Energy Systems

  Impinging Flames

The stimulated use of green fuels, bio-mass related fuels, in combustion systems needs, due to their low calorific content, the assistance of carriers such as propane or hydrogen. However, the use of these multi-components fuels is known to promote thermoacoutisc oscillations and to reduce the lean working region. Despite the knowledge on the effect of each of these individual fuels on flame dynamic behaviour and stability in combustion systems, it is difficult to envisage a simple weighted rule to predict the influence of fuel blends on burners lean limit and onset/characteristics of thermoacoutisc oscillations. This is because of the various thermal and chemical effects that may not be separable for fuel blends due to possible thermo kinetic couplings. Additionally, each of the major single fuels present in the mixture, has distinct and opposite burning behaviour (heat release, temperature and flame speed) function of stretch applied to flame and mixture Lewis number, making the analysis more difficult.

This topic reports on a combined mathematical and experimental investigation about the influence of fuel blends (methane, propane and hydrogen) on the onset/characteristics of thermoacoutisc oscillation of simple laminar impinging premixed flames. In this context, the main objectives of this work are:
  • To develop a transfer function for an unsteady flame dynamic behavior, burning fuel blends of different composition

  • To develop a mathematically model incorporating the flame and the burner acoustic models, to predict the acoustic resonant characteristics of the system
Representative results are reported in:
  • “The Visualization, Mapping and Mathematical Modelling of Unsteady Laminar Premixed Impinging Flames”, E.C. Fernandes and R. E. Leandro , Combustion and Flame 146 (2006), pp. 674-686.

  • E.C. Fernandes and R. Leandro (2004), The Visualization and Acoustics of Laminar Premixed Impinging Flame. Proc. 12th Int. Symposium on Applications of Laser Techniques to Fluid Mechanics, Lisbon, July 12-15, 2004.

  • E.C. Fernandes and R. Leandro (2004) Extended Satbility Regions and Acoustics of a Lean Laminar Premixed Impinging Flames. Poster. Lean Combustion Technology II: Promise and Practice. Engineering Conferences International, April 25—29, 2004, Tomar, Portugal (