Numerical Simulation On Premixed Catalytic Combustion Of Methane In Micro-combustor

With the technology development of micro-electro-mechanical system, the influence of micro-apparatus on many realms is gradually obvious. Researches on micromation and micro-systems have been an important study subject now. The micro-engine capability of producing 10-100W of power in a volume about 1cm3 has brought prevalent attention of world countries in recent years. With the advantages of high power density, longevity, small volume, light weight and simple fabric, micro-engine will have immense positive influence on micro-electronics, communication, biology and so on.Methane, which has the advantages of high power density and cheap cost, will be the main fuel of micro-gas-engine in next decades. Because of small dimension and high rate of heat loss, traditional homogeneous reaction can not carry through steadily. The research of methane premixed catalytic combustion in micro-combustor lays the foundation for the technology of hydrocarbon-fueled combustion in micro-engine.Micro-combustor was made up of four stainless steel pieces by using electro discharge machining technology, and it was composed of premixing-chamber and combustion-chamber. Numerical simulation of catalytic combustion, flow and heat transfer in micro-channels of three-dimensional micro-combustor was done in detail by using laminar finite-rate and second-order upwind discretization model. Catalytic combustion of methane/air mixture in micro-combustor was studied by changing the fabric of premixing-chamber, mass flow rate of methane, coefficient of excess air and wall boundary condition.The results indicate that gas flow is laminar flow. Catalytic combustion is mostly happened on the downside wall of combustion-chamber. Surface catalytic combustion is different from homogeneous combustion. There is no flame area, and temperature distribution is laminar. Fabric of premixing-chamber has influence on premixing effect, but it has little influence on conversion rate of methane.Conversion rate of methane increases while mass flow rate of methane decreases. While wall temperature is low, heat load firstly increases and then decreases. While wall temperature is high, heat load increases.Coefficient of excess air is the important influence factor of catalytic combustion in micro-combustor. While coefficient of excess air increases, conversion rate of methane firstly increases and then decreases. There is an optimal coefficient of excess air. Optimal coefficient of excess air increases, while catalytic wall temperature increases and mass flow rate of methane decreases.Catalytic wall temperature is the primary influence factor of catalytic combustion in micro-combustor. Catalytic reaction rate and conversion rate of methane increases immediately, while catalytic wall temperature increases.While methane/hydrogen mixture is injected into micro-combustor, catalytic reaction rate of hydrogen is high, and the combustion of hydrogen is complete. While hydrogen ratio increases, conversion rate of methane decreases. Conversion rate of methane/hydrogen increases, and heat load increases immediately.