Numerical Simulation On Catalytic Combustion Characteristic Of CH₄/Air Premixed Combustion In Heat Recirculation Micro-Combustor

Micro-scale combustion is studied to meet the requirement and development condition of Power-Micro Electro Mechanical System in automobile, electricity, aviation, military field and so on. The Power-MEMS has the characteristics of high energy density and long life. The combustion characteristic study of micro combustor is research foundation to achieve high efficiency and stable sustained combustion. In recent years, researchers have increasingly study on the micro-combustion, especially on catalytic combustion of methane in micro scale, but there are still a number of scientific and technical problem needs to be resolved.The paper focuses on methane and air premixed combustion characteristic and stability in micro-scale combustor, and the paper is preformed numerical simulation for catalytic combustion of methane. First, recently research status of micro-combustor combustion are reviewed at home and abroad. Then the problems on micro-combustor combustion research, which will be faced with of is analyzed and summarized, while it puts forward the future research direction that need to improve and strengthen. The paper analyzes the influence of the surface reaction, fluid velocity, surface parameters and geometrical parameters on the methane catalytic combustion. For plane micro-combustor, bring forward an improved project named“the structure of heat recuperation and excess-enthalpy”. Three-dimension numerical simulation of premixed combustion in micro-combustor is studied. Through choosing appropriate combustion chamber geometry shape, wall material, initial condition and controlling heat loss can achieve stability combustion of methane in micro-combustor, supplying theoretic gist and reference value for further designing and optimizing micro-scale combustion.Firstly, numerical simulation was done for catalytic combustion of methane/air mixture in conventional micro-combustor and heat recuperation micro-combustor, influence of relational factors on catalytic combustion was studied by the numbers and got conclusions as: the preheating channels structure can intensify heat transfer efforts to premixed mixture in the inlet channels from the exhaust gas, and the heat recuperation micro-combustor is beneficial to improve the extinction limit, methane conversion rate and achieve complete catalytic combustion. Equivalence ratio is primary factor, methane conversion rate will increase firstly and decrease secondly as the equivalence ratio increased.Secondly, numerical simulation was done for wall materials and the convective heat transfer coefficients in heat recuperation micro-combustor, the result of relational factors on catalytic combustion of methane/air was studied by the numbers and got conclusions as: a change of the material of combustor significantly affect the combustion stabilization of methane. The average temperature of quartz(smaller thermal conductivity) is slightly higher than that of the red copper(larger thermal conductivity). In addition, at a higher thermal conductivity, the temperature distribution of combustor is uniform and improve the heat concentrated distribution phenomenon, while the heat recirculation zone in the combustor can be reduced. Although the convective heat transfer can facilitate catalytic combustion steadily at a certain velocity range, it can simultaneously lead to decreasing the critical value of speed and average temperature, and the methane conversion rate will increase firstly and decrease secondly as the convective heat transfer increased.Thirdly, numerical simulation was done for baffle length and baffle angle θ in heat recuperation micro-combustor, the result of relational factors on catalytic combustion was studied by the numbers and got conclusions as: an increase of baffle length can increases methane conversion rate and average temperature of burner, but it reduces methane conversion speed, and methane conversion speed will increase firstly and decrease secondly along the axial direction of the burner. Then the research indicates that the baffle angle θ of burner can significantly influence the distribution of flow velocity field, and further effect on the distribution of temperature field, which cannot be ignored.In this paper, a relatively comprehensive investigation on the catalytic combustion process of methane, heat loss and geometrical parameter on the combustion of methane are conducted numerically, the effects of operating conditions, wall conditions and structure parameters on stable combustion characteristic are obtained. This article’s research is helpful to improve and optimize the micro combustor, and it promotes depth study of micro-scale combustion technology. It has certain academic significance and engineering value in the design of micro devices.