About Flameless combustion
Christophe Duwig
R&D Division, Haldor Topsøe A/S
and
Div. Fluid Mechanics, Lund University
Abstract:
Flameless combustion is a promising technology with great potential in term of reducing fuel consumption, pollutant emissions and improving operation flexibility in combustion devices including furnaces, gas-turbine burners and even piston engines. Departing from traditional burner (flame-based), the flameless regime focuses on much diluted reactant mixtures avoiding steep concentration or temperature gradients. Instead of a thin flame sheet, the oxidation is distributed over a large fraction of the combustion chamber. It is possible by recycling a large fraction of product/vitiated gases and mixing them with the reactants keeping the reactant concentration low and the temperature adequate for chemical reactions to proceed. The challenge is therefore to find the perfect balance in term of dilution to ensure proper operation. Unfortunately, only few studies have addressed the oxidation details in the reaction volumes under flameless combustion and almost exclusively under oxygen depleted conditions (i.e. fuel-rich). Hence, more studies are required in order to master this new combustion technique and develop further new generation of combustion devices.
Beside presenting Flameless combustion in general terms, this presentation will also highlight recent results obtained in a collaboration between Haldor Topsøe A/S and Lund University (Lund, Sweden). This project uses a newly developed burner located at Lund University operating at fuel lean conditions and at temperature levels relevant to low-NOx combustion devices. The burner enables to browse from flame-combustion to flameless-combustion making it a strong ground for advanced studies. Examples of advanced laser diagnostics imaging (PLIF and Rayleigh Scattering thermometry) as well as Large Eddy Simulation with relatively detailed chemistry will be presented in order to illustrate the turbulence-chemistry interaction during flameless-combustion.
The worked was performed in collaboration with Bo Li; Zhongshan Li & Marcus Aldén, Div. Combustion Physics, Lund University