Catalytic combustion characteristics of CH ₄ in the micro cavity‐combustor under different types of air inlet distribution

Abstract

There are combustion difficulties and combustion instability problems in micro-scale combustion due to the size effects. Focusing on the problem of combustion instability in micro-scale, on the basis of catalytic combustion, the recirculation zone (RZ) is constructed by cavity and the effect of RZ is enhanced by gas inlet at cavity wall to keep the stability of combustion. The total conversion of CH 4 in multi-inlets channel with cavity was higher compared with single inlet channel and single inlet channel with cavity. Numerical analysis was carried out to study the effects of total gas intake quantity (TGIQ), the excess air coefficient (EAC) and the air distribution mode, respectively. With the increase of TGIQ, the area of RZ increased gradually and a third RZ was gradually formed in the cavity. When the TGIQ gradually increased to 0.1828 mg/s, the combustor temperature increased significantly and as it continued to increase, the combustor temperature had little change. The highest temperature in combustor decreased gradually and the severe reaction zone moved from the back section of the combustor to the front with the increase of EAC. Moreover, the concentration of OH in cavity increased gradually and the mass flow rate of CH 4 in cavity decreased gradually. Increasing the air volume on the back cavity wall, the high-temperature zones and concentration of OH in cavity continuously improved when the TGIQ was same. The combustion process was enhanced and the catalytic reaction was stabled. The temperature of main channel first increased and then decreased.

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