Experimental Study on Combustion Characteristics of Lean Methane-air Mixture in a Combustor Filled with Staggered Alumina Cylinders

Abstract

ABSTRACT The premixed combustion of lean methane-air mixture in a structured porous combustor filled with alumina cylinders was experimentally studied. The alumina cylinders with a diameter of 6.5 mm and a height of 19.5 mm were regularly staggered placed in the combustor and the average porosity of the packed bed was approximately 0.43. The characteristics of interest were the temperature distribution, the peak combustion temperature, and the combustion wave propagation velocity. The parameters investigated that affect these characteristics included gas inlet velocity and equivalence ratio. Results indicated that the combustion wave propagation was stable and super-adiabatic combustion phenomena were observed under the test conditions of the equivalence ratios in the range of 0.162–0.324 and inlet velocities in the range of 0.43–0.86 m/s. The lean flammability limit was extended to an equivalence ratio of 0.162 at the inlet velocity of 0.43 m/s. The larger equivalence ratio and inlet velocity can supply more fuel to be sufficient combustion, resulting in the higher peak combustion temperature. The combustion wave propagation velocity was inversely correlated with the equivalence ratio. With increasing inlet velocity, the combustion wave velocity increased. The order of magnitude of the combustion wave velocity was 0.1 mm/s. The pressure drop across the structured porous packed bed was remarkably smaller than that of the random one.