Flow stabilized porous heterogeneous combustor. Part II: Operational parameters and the acoustic emission

Pd enhanced WC catalyst to promote heterogeneous methane combustion

“…For flame ignition, the combustor reactants were delivered to the inlet of the combustion chamber at a total flow rate of ̇= 27.15±0.61 SLPM and equivalence ratio of φ=1.00 ±0.02, then a pilot flame was introduced at the exhaust. Reactant flow rates were kept low to enable propagation of the flame to the combustion chamber inlet from the ignition point at the exhaust [27]. Once the flame was positioned between the reactant inlet and porous media, the reactant flow rate was increased to ̇= 51.59±0.61 SLPM and equivalence ratio lowered to φ=0.80±0.02 to prevent the development of a standing acoustic wave in the combustion chamber [27] and to position the flame within the pores of the porous media while still maintaining a rapid heating rate.…”

“…Reactant flow rates were kept low to enable propagation of the flame to the combustion chamber inlet from the ignition point at the exhaust [27]. Once the flame was positioned between the reactant inlet and porous media, the reactant flow rate was increased to ̇= 51.59±0.61 SLPM and equivalence ratio lowered to φ=0.80±0.02 to prevent the development of a standing acoustic wave in the combustion chamber [27] and to position the flame within the pores of the porous media while still maintaining a rapid heating rate. Once the combustion chamber was saturated with heat, the air flow rate was held constant but the methane flow rate was reduced, shifting the equivalence ratio from φ=0.80±0.02 to φ=0.75±0.02.…”

“…As in previously reported experiments where α-Al2O3 ceramics was utilized as porous media [10] or MSZ coated with WC-Pd powder [34], ignition of the flame inside the combustion chamber was initiated shortly after the experiment begun using a torch. Upon ignition, the flame front proceeded toward the reactant inlet rapidly [27,34].…”

“…become positive over the axis of the combustion chamber; indicating the combustor is operating in a different mode from all other observed behavior[10,26,27,34]. In this second observed mode, low temperature chemical reactions, which are assumed to occur primarily on the catalyst surface, enabling some small quantity of heat to be released.…”

“…To perform the experiments CH4 and air mixtures are delivered to a heterogeneous combustor, described in extensive detail elsewhere [26]. The temperature profiles are measured within the combustion chamber using thermocouples while an external microphone is used to collect and characterize acoustic signatures of combustion along with a CCD camera which is used to photograph light emitted from the porous media which is visible through the combustion chamber exhaust [26,27] Oberkochen, DE) equipped with EDS detector (IXRF Systems: Austin, USA), which allowed for evaluation of chemical compositions of the powder.…”