Study On Combustion Stability Of 1 KW Solid Oxide Fuel Cell Stack Exhaust Gas

Due to the advantages of high power generation efficiency,wide fuel applicability,green pollution and high energy density,solid oxide fuel cell（SOFC）is known as one of the most promising power generation technologies in the 21st century.In SOFC system,the stack tail gas combustion chamber provides the required heat for the SOFC system,the stable combustion of stack exhaust gas is the key foundation for stable long-term operation of SOFC system.Metal fiber burner is particularly suitable for lean combustion of stack exhaust gas under various operating conditions of SOFC due to its strong heat storage capacity,good durability,strong flexibility,good porous structure and combustion emission characteristics.However,there are few studies on the combustion stability of metal fiber burner and its application in SOFC.To this end,this thesis conducted the following research:In the experimental bench of solid fuel battery combustion system,the stable combustion range of 1～6 k W power syngas（component:77%H₂ and 23%CO）in the metal fiber burner with a diameter of 50mm was determined by experiment and numerical calculation under the preheating condition of 450°C,and the combustion stability index（CSI）was introduced as the evaluation of combustion stability.The numerical simulation results show that when the fuel utilization ratio（U_F）in 0～0.6while reforming water-carbon ratio（S/C）in 1.8～3,the variation of flame propagation velocity is more than 10 times,while the variation of gas flow at the burner outlet is only about 1.2 times.In the start-up stage of SOFC system,the flame propagation velocity is much higher than the outlet velocity,and there is a possibility of flash-back.When full power generation,the decrease of flame propagation velocity is much larger than that of outlet velocity,and the risk of blow-out increases.According to the combustion characteristics of stack exhaust gas and stable combustion index,the appropriate metal fiber burner is determined.The combustion stability of 1k W-SOFC system and the effect of water-carbon ratio fluctuation（1.8～3）on the combustion stability were studied in U_F between 0～0.6.Experiments show that when the fuel utilization rate is 0～0.4,additional air is needed to stabilize combustion.The increase of water-carbon ratio increases the risk of blow-out.In the rated power generation state,that is,U_F is 0.6,even if S/C is 3.0,Due to the good heat storage capacity of the metal fiber burner,the burner can still burn stably without flame separation.Through the above research,this thesis realizes the stable combustion of the reactor tail gas of the rated power 1 k W-SOFC system under the full working conditions of S/C between1.8～3 and U_F between 0～0.6.The research results are helpful to improve the stability and long-term operation time of SOFC fuel cell system.