【作者】 王恩宇；

【导师】 骆仲泱； 倪明江； 岑可法；

【作者基本信息】 浙江大学 ， 工程热物理， 2004， 博士

【摘要】 为缓解能源结构不合理造成的环境污染问题，我国加快了天然气的使用力度，发展高效、低污染排放的天然气燃烧技术具有非常重要的现实意义。气体燃料在惰性多孔介质中的燃烧技术在很多方面体现出了其优越性，成为近年来燃烧领域的研究重点之一。 本文以实现高效、稳定燃烧和低污染物排放为目标，研究了多孔介质猝熄直径、孔径、厚度等参数对均匀多孔介质(HPM)中燃烧特性的影响规律；提出了渐变型多孔介质(GVPM)结构优化的设计构想，研究了气体燃料在渐变型多孔介质中的燃烧和流动特性。 对均匀多孔介质中预混火焰的猝熄效应进行了试验研究，发现多孔介质的猝熄直径是多个参数的复杂函数，与混合气体流速、层流火焰传播速度、燃烧室管流雷诺数、预混气体导温系数、当量比、多孔介质固体温度有关。采用孔径由小到大逐渐变化排列的渐变型多孔介质，可以扩大多孔介质内火焰的猝熄范围，增强燃烧的稳定性。 对均匀型多孔介质中的燃烧稳定性进行了试验研究，得到了均匀多孔介质中回火、脱火或熄火的当量比极限范围；研究了火焰从多孔介质下游外侧进入多孔介质内部或火焰从多孔介质中脱离或熄灭时的气流速度或当量比极限条件；得出了火焰面位置及燃烧温度随当量比和燃烧强度的变化而在多孔介质中移动的规律；同时，在试验中发现了火焰的偏移、分层或分块燃烧现象，从另一方面说明了多孔介质中温度分布均匀和污染物排放降低的原因所在。 进行了泡沫陶瓷孔径、厚度及材质对均匀型多孔介质中的稳态燃烧特性的影响试验研究。得到了多孔介质孔径对燃烧室温度分布、污染物排放、火焰速度、燃烧稳定性以及多孔介质燃烧器压降(阻力损失)的影响规律和多孔介质层厚度对燃烧器换热特性及阻力特性的影响规律。均匀多孔介质中燃烧特性的研究为渐变型多孔介质的设计和燃烧特性的研究奠定了基础。 对天然气—空气预混气体在多种渐变型多孔介质中稳态燃烧特性、启动特性、非稳态特性进行了详细研究。获得了渐变型多孔介质中的温度分布、污染物排放、火焰速度、燃烧稳定性及压降随当量比和燃烧强度的变化特性，并研究了渐变型多孔介质中稳定燃烧的气流速度和当量比极限；通过燃烧室温度分布揭示了渐变型多孔介质中稳态燃烧状况的多样性存在。试验结果表明，采用合适的渐变型多孔介质结构可以改善单一孔径多孔介质中的燃烧特性和流动特性，使燃烧室温度分布更加均匀，同时也可以提高燃烧稳定性，提高火焰速度，拓宽可燃当量比极限范围；在污染物排放方面，也由于对温度分布的改善而使得污染物排放更低。根据GVPM燃烧室中温度分布随燃烧强度的变化特性，给出了多种GVPM燃烧器的推荐燃烧强度范围。发现GVPM燃烧器的启动受到多孔介质结构、燃气流量、当量比、点火位置及多孔介质初始预热条件等因素的影响。通过多孔介质中的非稳态试验发现，对多孔介质预热条件下可以维持恶劣工况较长时间运行，这为采用预热式或循环往复式燃烧极贫燃料的实现提供了一定的试验基础。浙江大学博士学位论文王思宇，2004.4 考虑了多孔介质的粘性力、惯性力及形状效应，以多孔介质中燃烧的基本方程为基础，推导出了多孔介质中的湍流燃烧模型。通过“用户自定义函数”对Fluent 6.1软件包进行了创新性的改进用于模型的求解。对多种均匀型多孔介质和渐变型多孔介质中的燃烧过程进行了模拟，得到了温度场、速度场、浓度场以及NO排放和多孔介质燃烧器压力损失的数据，分析总结了多孔介质孔径、厚度及孔排列结构对燃烧特性的影响规律，并与相关的试验结果进行了对比;对模型的理论预示结果和试验结果的差异进行了分析和解释。最后，对本文采用的理论模型进行了分析评价。关键词:多孔介质预混燃烧渐变型多孔介质燃烧器天然气气体燃料湍流燃烧模型更多还原

【Abstract】 The natural gas is being exploited and utilized rapidly for solving the serious environmental pollution problem due to the bad energy structure in our country. To develop the technique of natural gas combustion with higher efficiency and lower pollutants emission becomes very significant. The technique of fuel gases combustion in inert porous media has many advantages, and becomes an important topic in combustion research field.In this thesis, with high efficiency, stable combustion and low pollutants emission for goal, a idea of gradually-varied porous media (GVPM) was put forward, and the characteristic of the gaseous fuel/air mixture flow and premixed combustion in the GVPM was studied detailedly, based on the study on the influence of the quenching diameter, pore size and thickness of the porous ceramic foam to the characteristic of the natural gas/air premixed combustion in the homogeneous porous media (HPM).Experimental studies are done for the quenching effect of premixed flames in the HPM. It was found that the quenching diameter of porous media is a multi-parametric complicated function, related to the mixture flow speed, the premixed gaseous laminar flame velocity, the pipe flow Reynolds numbers, the coefficient of temperature conductivity, the equivalence ratio and the solid temperature. To make a GVPM with the pores increasing gradually, the quenching diameter range will be expanded and the stability of the flame in it be enhanced.The stability of premixed combustion in HPM was studied experimentally. The flashback, blow-off or extinction equivalence ratio limits were gained for the HPM burner. Similarly, the gas flow speed or the equivalence ratio conditions were studied, which of the flame into the HPM from outside or of the flame away from the HPM. The laws of the flame position and the temperature in the HPM changing with the equivalence ratio or the firing rate have been gained. During the experiments, the phenomena of the flames were observed to be excursion, separate layers or blocks burning. The existence of these phenomena may be one reason of the uniform temperature distribution and low pollutant emission in the porous media..The influence of the pore size, thickness and materials to the characteristics of stable combustion in the HPM were studied experimentally. The influence of the mean pore diameter of the HPM to the temperature distribution in the combustors, pollutants emission, flame speed, burning stability and the pressure drop (resistance loss) were gained. As the case of the HPM with 30 PPI, the influence of the HPM thickness to the characteristics of heat exchange and the resistance of the HPM burners were studied. The studies on the combustion characteristics in the HPM are the base for designing the GVPM and studying the combustion characteristics in the GVPM.A systematic research was carried out on the characteristics of natural gas/air mixture steadily combusting in the GVPM burners. The contents included temperature distribution, pollutant emission, flame speed and pressure loss, as the functions of the equivalence ratio and firing rate, moreover, the gas velocity and equivalence ratio limit for steady combustion in the GVPM burners. There is multiplicity for steady combustion available, which can be indicatedby temperature distribution in the burner. The startup and unsteady combustion characteristics of the GVPM burners were also studied. The experimental results show that the combustion and flow characteristics in porous media burners can be improved by using a suitable GVPM structure. More uniform temperature distributions, better combustion stability, faster flame speed and broader limit range of equivalent ratio were achieved for a GVPM than those of HPM. Meanwhile, lower pollutant emission is realized due to amendatory temperature distribution.The temperature distributions of different characteristics in the GVPM burner can be found under various firing rates. After analyzing the experimental results, the recommended ranges of firing rates for the burners with different GV更多还原