One solution to intensify heat recirculation in a premixed
burner
and, thus, to enhance the flame stability is to employ porous inert
material. Through the highly stable premixed flames low temperature
combustion can be achieved employing high excess air ratios which
beneficially results in a reduction of the NO
x
formation by the thermal pathway. Additionally, minimization
of temperature and flow inhomogeneities, insensitivity to the fuel
supply fluctuation, and damping of flow pulsations are beneficial
properties of a porous burner leading to high power dynamic range.
Heat transport properties of the solid porous inert media and the
strongly tortuous flow path through this structure play a key role
for the internal heat recirculation and for flame stabilization as
its macroscopic manifestation. These properties strongly depend on
the structure geometry and/or physical properties of the material.
With an aim to quantify the contribution of the basic physical processes
in a porous burner and to optimize its performance the present work
reveals a comprehensive experimental study on the flame stability
and emissions of such a burner containing different reticulate ceramic
sponge structures. It was shown that in order to quantify the contribution
of each heat transport mechanism of the global heat recirculation
phenomenon and to estimate its relative importance experiments along
a three-dimensional matrix (geometry, material, thermodynamic conditions)
are required. The quantification of each relevant heat transport mechanism
contribution was achieved using one-dimensional volume averaged analysis
and comparison with experiments. Furthermore, such comprehensive experimental
data with defined boundary conditions provide a necessary prerequisite
for numerical validation cases.