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2007-06-13 - Colloque/Présentation - poster - Anglais - 1 page(s)

Lupant Delphine , Pesenti Barbara , Lybaert Paul , "Detailed Characterization of Flameless Oxidation on a Laboratory Scale Furnace" in 15th IFRF Members' Conference, Combustion in an efficient and environmentally acceptable manner, Pisa, Italy, 2007

  • Codes CREF : Recherche énergétique (DI2290), Combustion (DI2212)
  • Unités de recherche UMONS : Thermique et Combustion (F704)
  • Instituts UMONS : Institut de Recherche en Energétique (Energie)

Abstract(s) :

(Anglais) Flameless Oxidation is a combustion technology developed in the early nineties to abate nitrogen oxides emissions in industrial furnaces. The advantage is that combustion air can be preheated at high temperature what generates a better combustion efficiency without exceeding the maximum level of NOx emission. The principle is based on the entrainment of flue gas by the high velocity reactant jets. This dilution reduces reactant concentrations as well as temperature peaks and consequently minimizes the NOx formation. This combustion mode has been rapidly applied to industrial burners, but its deep understanding and its numerical modeling is still under investigation. The present study handles with a laboratory scale furnace operating in Flameless Oxidation. The objective is to create an experimental database that will help to understand this combustion mode and that will be used for the validation of the numerical models. The small scale of the furnace and the stationary state of the burner make the measurements easier, and the reduced computational domain leads to a shorter computational time. The furnace volume is about 3m³. Four sliding water cooled tubes feature the load and their immersion depth regulates the furnace temperature. The combustion air is preheated electrically (up to 1000°C) and is injected in the centre of the square base of the furnace. Two natural gas injectors are laid on both side of the air injector. The gas firing rate is around 30kW. The experimental characterization is done thanks to wall temperature measurements, OH self emission visualization in UV, as well as temperature and species concentration field measurements in the furnace vertical plane (O2, CH4, CO, CO2 and NOx content). With a small scale furnace, the intrusive character of the probe is considerable and the probe has to be the most appropriate to ensure the good quality of the results. The paper deals with the differences obtained for the concentration fields following the configuration of the sliding probe used (completely cooled or not, effect of the suction orifice diameter). Moreover the furnace is modeled using the CFD commercial code Fluent. Experimental boundary conditions are introduced, and the numerical results are compared to measurements to validate the numerical models. The standard k-e model is used for the turbulence and the discrete ordinates model for the radiative heat transfer. Different sets of parameters are tested in the Eddy-Dissipation/Finite Rate combustion model, and their influence on the results is discussed. The objective is to find the model able to predict the most accurately possible the shape of the reaction zone and its location. These characteristics are specific to the Flameless Oxidation mode.