Numerical Simulation Study On Catalytic Combustion Of Methane In Micro-chamber

With the development of the micro-electronics machine system (MEMS) technique, influence of the micro machine on many realms is gradually obvious. Researches on miniaturization and the miniature system have become the important study in recent years. The domestic and international research organizations have developed the research about micro-electronics machine system (MEMS) and micro-engine.Based on the analyzing of the main factors that have affect on stability and efficiency of combustion in micro chamber, then we design and carry on to process the micro chamber by using electrical discharge machining. Catalytic combustion of methane/air mixture in micro-chamber plating Pt catalyst was investigated numerically by changing the temperature, equivalence ratio of methane and mass flow-rate of inlet.The results indicate that wall temperature is the most important factor for catalytic combustion in micro-chamber. Conversion rate of methane increases as the temperature increases. Temperature influence on catalytic combustion is different when equivalence ratio of methane is different. The less equivalence ratio of methane is, the higher temperature influence on conversion rate of methane is. So, it is important to enhance the wall temperature as possible when catalyst is in effect.Appropriate equivalence ratio of methane is a key factor for the combustion in micro-chamber. Conversion rate of methane increases firstly and decreases secondly as the equivalence ratio increases,which means there is a most appropriate equivalence ratio of methane. The equivalence ratio that can achieve optimal conversion rate of methane is different at different wall temperature. In order to obtain a good conversion rate of methane, the equivalence ratio of methane is in 0.8- 1.0.The conversion rate of methane decreases when mass flow-rate of methane increases in the micro chamber. When mass flow-rate of methane increases, mass flow-rate and velocity of mixture increases, which can reduce the contact time between mixture and surface of catalyst enormously, catalytic combustion on the surface is insufficient.The conversion rate of methane in catalytic combustion is 150 times than gas-phase combustion. So, gas-phase combustion may be ignored. When coupling reaction is considered, the mixture diffuses quickly to the catalyst surface, concentration of methane in the mixture becomes lowly, which makes the reaction rate of gas-phase combustion decreases. Catalytic combustion can reduce gas phase combustion rate. The conversion rate of methane in the micro-chamber is 95% when equivalence ratio of methane is 0.8 and the wall temperature is 1200K.