The paper described the combustion characteristics in a multi-staging vortex combustor by using rice husk as fuel. Effects of the operating conditions namely: equivalence ratio (Φ=0.8, 1.0 and 1.2) and secondary air ratio (λ=0.0, 0.15 and 0.25) on combustion characteristics (temperature distribution, fly ash and gas emission) were experimentally studied. In the experiments, the conventional vortex combustor consisted of two straight concentric cylindrical pipes, combustion chamber (outer chamber) and exhaust pipe (inner chamber). The variable size of middle section of the combustor was designed to be adjustable from 1.0D (conventional vortex combustor), to 0.75D and 0.5D as desired. The changes of the middle chamber size lead to multi-staging vortex inside the combustor. In the experiments, the rice husk was fed into the combustor at constant mass flow rate of 0.3 kg/min. Test results revealed that the mean temperature distribution for the multi-staging vortex combustor with middle chamber size of 0.5D was higher than those of 0.75D and 1.0D. The experimental results showed the maximum temperature of about 1176 ℃ in the vortex chamber with the middle chamber of 0.5D at equivalence ratio, Φ=0.8 and no secondary air injection, λ=0.0. Measurements of gas emissions from cyclone collector consisted of O_2=2.5%, CO_2= 17.3%, and CO=270 ppm, respectively.
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