Porous burners for low emission combustion: An experimental investigation

Porous media combustion offers significant advantages against free flame burners, concerning pollutant emissions, power density, turn down ratio, combustion stability and the potential to operate in ultra-lean combustion regimes. The objective of the present work was to perform a comprehensive experimental characterization of a state-of-the-art porous burner in terms of thermal efficiency and pollutant emissions and assess its operating limits. The combustor was a rectangular two-layer porous burner with an Al2O3 flame trap and a 10 ppi (pores per inch) SiSiC foam. The burner was operated with methane and LPG. An extensive stability mapping was performed in order to establish its range of operation in terms of thermal loads and mixture equivalence ratios. Gas phase temperature profiles were measured using thermocouples and the solid phase temperature distribution was obtained using an IR camera. Gaseous emissions were quantified using an online gas analyser sampling system. The results revealed a homogeneous temperature distribution, low NOx and CO emissions and wide flexibility with respect to fuels and thermal loads. The effects of fuel interchange on efficiency and emissions were also analysed. Finally, the relative impact of thermal load on temperature and emission values, with respect to equivalence ratio or fuel type, is discussed.

► The work performs a comprehensive experimental characterization of a porous burner in terms of thermal efficiency and pollutant emissions.
► The burner was tested with methane and LPG as fuels under various thermal loads and equivalence ratios.
► The conditions studied correspond from flashback up to (nearly) blow off operational conditions.
► It was observed that the flame stabilizes inside the porous structure providing high turn down ratio and enhanced combustion stability.
► Exhaust gas and solid phase temperature profiles were measured, and CO and NOx emissions were monitored using a gas analyzer.