Numerical And Experimental Studies Of Catalytic Combustion Of Methane In Micro-combustor

With the development of the micro-electronics machine system (MEMS) technique, the micro machine has an important influence on many areas. Researches on miniaturization and the miniature system have become an important study in recent years. The domestic and international research organizations have developed the research about micro-electronics machine system and micro-engine. With the advantages of high power density, long life span, small volume, light weight and simple fabric. At the beginning of its study from the middle of the 1990's in China, there are still a number of scientific and technical problems need to be resolved. For instance,the flows,combustion time, combustion efficiency and stability of fuels in micro space may have a completely different combustion characteristics in the large space, which require further study. 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 removal, regular homogeneous reaction can not carry through steadily. The study of the flow and catalytic combustion of methane in micro-combustor lays the foundation for the technology of hydrocarbon-fueled combustion in micro-engine.Based on the analyzing of the study status and main problems of flow and combustion in micro-system,the technology of rotational flow,premixed,catalytic reforming and combustion in micro combustor is presented. The characteristics of micro-flow and mechanism of catalytic reforming and combustion reaction are analyzed. The premixed effect in micro-premixed chamber is investigate using the several factors of fuel inlet diameter, numbers of arc-shaped and straight channel, the distance and number of subordinate fuel inlets. The influence of different factor on export velocity, uniformity coefficient of flow distribution and premixing coefficient in the export of the chamber are discussed. Which provides a theoretical basis for the designing a high efficient micro-premixed device.The premixing methods and structure of micro combustor are optimized to increase the gas settle time in combustion chamber. Under the nickel catalyst, the catalytic reforming and coking characteristics of methane and water vapor in the premixed chamber have been gained. The appropriate range of the control parameters (such as catalyst temperature, stream/methane ratio and the quality flow) has been gained. For different purposes and catalytic reaction, the catalytic combustion strategy of the micro-premixed chamber and combustion chamber were coated with different types catalyst is proposed. The relations of Kn and the characteristics of gas flow and heat transfer in slip area are firstly studied.The standard of reaction for the selective of CO and CO₂ can be used to assistantly assess and analyze the methane catalytic combustion efficiency and the utilization level of heat. Under the conditions of micro-scale, the impact of space reaction on the whole catalytic reaction can be ignored. The influence of catalytic surface temperature, nCH₄/O₂ mole ratio and mass flow rate on the methane catalytic combustion efficiency has been gained. The influence of the reaction on CO and CO₂ selectivity and utilization level of heat has been gained. It has an important reference value for improving the micro-scale catalytic combustion efficiency and thermal utilization level.The influence of different catalytic wall, flow nonuniformity and mixing nonuniformity on catalytic combustion are firstly studied in the combustion chamber. In the combustion chamber structure of text, when the catalytic surface temperature, CH₄/O₂ mole ratio and mass flow rate changes, the influence of different catalytic wall on the methane catalytic combustion efficiency has been gained. Accounting the efficiency of catalytic combustion and catalytic cost, the catalytic coating strategy on different catalyst walls is put forward. The influence regularity of flow nonuniformity, mixing nonuniformity and hydrogen on catalytic combustion and catalyst life are gained. It offers effective measures for the enhancing catalytic combustion efficiency and reduces catalyst costs in micro-scale.The micro-premixing chamber and combustion chamber are optimization designed and fabricated using EDM processing technology. The experiment system of the micro combustor has been set up and the pipeline connections are simplified, which improved micro-scale combustion stability, combustion efficiency and operability. Under different micropore diameter and methane flux conditions, the methane diffusion and premixed flame were experimentally investigated. The change regularity of flame length with methane flux, micropore diameter and Reynolds number is found. The relation of the blow-off and quenching speed of methane diffusion flame and stable combustion regions and the aperture diameter was discussed. The relation of flame length/micropore diameter ratio (L/d) and the Reynolds number was gained. In the stability of high temperature environments provided by the experimental systems, the influence of the catalytic temperature, CH₄/O₂ molar ratio and the methane flux on the methane catalytic combustion efficiency has been studied and compared with the numerical simulation results. It further revealed the heat loss plays an important role in the micro-scale catalytic combustion. It also affords an important reference and experimental foundation for the study of hydrocarbon fuel combustion characteristics in micro-scale systems.This paper studies the micro-scale flow, premixed, catalytic reforming and burning issues and analyzes micro flame shape and structure, quenching characteristics and catalytic combustion in constant temperature environment. The measures of improving micro-scale premixed, catalytic reforming, combustion efficiency, micro-space heat exchange and heat loss reduction are put forward. And the change relation of they and the influencing factors have been gained. It is helpful for deeper investigation of the micro-scale catalytic combustion. The results not only enrich the researches on micro-scale catalytic combustion, but also provide reference for the development and application of relative technologies. It also establishes the foundation for the micro-engine hydrocarbon fuel combustion technologies and promotes the development of micro-generation power system. The results have an important academic value and engineering applications.