【作者】 闫云飞；

【导师】 张力；

【作者基本信息】 重庆大学 ， 动力工程及工程热物理， 2008， 博士

【摘要】 随着微电子机械系统（MEMS）技术日新月异的发展,微器件对许多领域的影响日趋明显,装置的微型化与微型系统的研究已成为当今研究的重要课题。近年来,国内外科研机构相继开展了微动力机电系统和微发动机的研究工作。它具有能量密度高、寿命长、体积小、重量轻、结构简单等优点。国内该领域的研究始于二十世纪九十年代中期,需要解决的科技难题还有很多。如微空间内可燃气体的流动、燃烧时间、燃烧效率和稳定性等可能与大空间内的燃烧有着完全不同的特性,这都需要进一步深入研究。甲烷燃料容易获得、价格低廉,在未来数十年内将是微型机电系统和气体发动机的主要燃料。微型燃烧器的尺寸较小、散热速率较大,可能使常规空间反应无法稳定进行,因此,研究微型燃烧器内甲烷预混流动和催化燃烧特性,可为微型发动机碳氢燃料燃烧技术打下基础。本文针对微系统内流动与燃烧的研究现状和存在问题,提出了微型燃烧器内碳氢燃料旋流预混催化重整燃烧技术,分析了微细尺度流动特性、催化重整及催化燃烧的反应机理。提出以燃料入口直径,旋、直流槽数量,次级燃料入口距离、数量等几方面因素来研究提高微型燃烧器预混腔的预混效果。探讨了了各参数变化时,各燃气出口速度、燃气出口速度分布均匀性、出口预混系数的变化规律,为设计快速高效的微型预混器提供理论依据。对预混方式及微燃烧器结构进行优化设计,增加了燃气在燃烧器内的停留时间,得到了甲烷、水蒸气在镍催化剂作用下在预混腔发生催化重整、积碳特性的变化规律。得出了影响其特性变化的控制参数（如催化温度、水碳比和质量流量）的适宜范围。针对不同的目的和催化反应,提出在微型燃烧器的预混腔和燃烧腔分别涂敷不同种类催化剂的催化燃烧策略。首次对滑移区内气体的流动与传热特性与Kn数关系进行了研究。提出可用反应对CO和CO₂选择性的指标,来辅助评价和分析各因素变化时甲烷催化燃烧效率和热值利用率的高低。微细尺度条件下可以忽略空间反应对整个催化反应的影响。得到了催化壁面温度、nCH₄/O₂摩尔比和质量流量变化时,甲烷催化燃烧效率、反应对CO和CO₂选择性、热值利用率的影响规律。对如何提高微细尺度下催化燃烧的燃烧效率和热值利用率具有重要的参考价值。首次考察了燃烧腔不同催化壁面、流动不均匀性、混合不均匀性对催化燃烧的影响。得到了在文中特定燃烧腔结构下,催化温度、甲烷与氧气摩尔比和甲烷质量流量各因素变化时,不同催化壁面对甲烷催化燃烧效率的贡献情况。为了兼顾催化燃烧效率和催化成本,提出了催化剂在不同催化壁面的涂敷策略。得到了流动不均、混合不均以及氢气量对甲烷催化燃烧和催化剂使用寿命的影响规律。为提高微细尺度下催化燃烧效率和降低催化成本提出了有效的解决措施。对微型燃烧器的预混腔和燃烧腔进行了结构优化设计,采用电火花加工工艺加工微燃烧器,搭建了微型燃烧器实验台,优化了系统,提高了微细尺度燃烧的稳定性、燃烧效率和可操作性。对不同微孔、不同流量下甲烷的扩散和预混燃烧火焰进行了实验研究。研究分析了不同工况下微火焰的形状、分布和颜色的变化情况。实验得到了火焰长度随甲烷流量、微孔孔径、微孔出口处雷诺数的变化规律。探讨了吹熄速度、淬熄速度、火焰的稳燃范围随孔径变化关系以及火焰长度/孔径之比随微孔出口雷诺数的变化规律。在实验系统提供的稳定高温环境下,研究了催化温度、CH₄/O₂摩尔比以及质量流量等不同因素对甲烷催化燃烧效率的影响,并分析了与数值模拟的异同。进一步揭示了散热损失在微细尺度催化燃烧中的重要作用。为微细尺度下碳氢燃料催化燃烧特性的研究提供重要的参考价值和实验基础。本文较系统地研究了微细尺度内流动、预混,催化重整及燃烧问题、研究分析了微孔燃烧火焰形状、结构及熄灭特性,微型燃烧器在稳定的高温环境中的催化燃烧等,提出了提高微细尺度预混、催化重整燃烧效率、充分利用微空间换热、减少散热损失的措施,并得到了相关影响因素的变化规律。有助于推进微细尺度催化燃烧特性的深入研究,充实和丰富了微细尺度催化燃烧的研究成果,也为相关技术（微旋流预混技术、微细尺度催化重整与燃烧等）的开发与应用提供了重要的参考依据。为微型发动机碳氢燃料燃烧技术打下基础,对推动微型发电动力系统的发展,具有重要的学术价值和工程应用价值。更多还原

【Abstract】 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.更多还原