【作者】 崔凯；

【导师】 岳光溪；

【作者基本信息】 清华大学 ， 动力工程及工程热物理， 2013， 博士

【摘要】 富氧高温空气燃烧（HTOEC）是具有前景的煤粉燃烧技术，研究其燃烧特性和NO_x生成特性具有重要意义。论文在文献调研的基础上，通过基础实验、样机试验和数值模拟对煤粉在富氧高温空气条件下的燃烧特性和NO_x生成特性进行了全面研究。论文首先使用TGA、沉降炉和携带流反应器等实验研究了富氧条件下对煤粉的燃烧反应动力学及着火特性的影响，而后重点地开展了HTOEC煤粉燃烧器样机的研制、性能测试和数值模拟工作。论文搭建试验台完成了样机的燃烧和NO_x排放性能试验；数值模拟了HTOEC样机的燃烧和NO_x生成与还原，模拟结果与试验数据一致。为提高模拟精度和节约计算成本，论文对煤粉湍流燃烧模拟进行了多项改进：（1）提出一种根据煤质参数估算煤挥发分组分的方法；（2）在均相反应和NO_x生成与还原模拟中考虑挥发分中间组分反应的影响；（3）应用Magnussen的熄火理论修正传统EDC模型；（4）提出并开发湍流煤粉燃烧的“双反应机理法”。论文主要结论如下：1）实验研究表明：氧气浓度和加热速率提高会缩短煤颗粒着火所需时间，降低着火温度，增强煤燃烧强度，提高燃尽率；2）样机试验表明：在煤粉燃烧器的浓股一次风预热室中加入一股富氧气流可以实现富氧高温空气燃烧，在氧消耗量很少的情况下可以实现优异的煤种适应性、燃烧稳定性、节油性能和低NO_x排放性能；3）数值模拟表明：在富氧高温空气燃烧条件下，煤粉气流的火焰温度增高，燃烧强度增强，挥发分析出加快，着火提前；使用少量的氧气也可实现煤粉NO_x排放浓度的大幅减小，NO_x排放浓度与富氧气流中的氧浓度的增大呈先减小再增大的非单调变化，对论文所设计的燃烧器，富氧浓度的最佳值在50%左右；4）在EDC模型中考虑挥发分中间组分反应和进行基于Magnussen的熄火理论的修正可提高对湍流煤粉射流着火和燃烧特性的预测精度，更加准确地描述了化学反应与湍流的相互作用；将应用骨架机理的EDC模型与传统“后处理法”相结合，经过试验数据修正后，湍流煤粉燃烧中NO_x生成与还原的模拟精度得以提高；将复杂化学反应机理局限于主反应区，而其它区域使用简单化学反应机理的“双反应机理法”可以显著提高计算效率，便于高精度修正EDC模型的工程应用。更多还原

【Abstract】 The oxygen-enriched and high temperature air combustion (HTOEC) is apromising pulverized coal combustion technology. In the paper, the combustion andNO_xformation characteristic of the pulverized coal under the high temperature andoxygen-enriched conditions was fully investigated through literature study, theoreticalanalyses and experimental study, model burner assessment and numerical simulation.First, in the laboratory, TGA, drop tube furnace and entrained flow reactor (Henckenburner) were used to study the combustion kinetic and ignition behaviors of the coalparticle in oxygen-enriched and preheating conditions. Then, a model HTOECcoal-fired burner was developed. A test rig was established and a set of experiments hasbeen conducted to validate the combustion and NO_xemission performance of the modelHTOEC burner. At the same time, corresponding studies were conducted numericallyby using the Eddy Dissipation Concept (EDC) model with several improvements, andthe predictions were consistent with the experimental results. And the improvements,which could be also applied to the general simulation of the turbulent combustion ofpulverized coal include (1) A new method to estimate the volatile content based on theproperties of the coal；(2) The consideration of the intermediate reactions of the volatilematter in the homogeneous reaction and NO_xformation;(3) Adoption of the extinctiontheory proposed by Magnussen to cease the homogeneous chemical reaction when itscharacteristic time scale is greater than that of the turbulence;(4) The noveltwo-mechanism-zone method.The main conclusions are as follows:1) Based on the laboratory experiments, the increase of oxygen concentration andheating rate could cause the reduction of the ignition time and ignition temperature ofthe pulverized coal particles, enhancing their combustion intensity and burnt-out.2) The HTOEC model burner experiments showed that with the special burnerstructure and proper flow organization, the HTOEC method can be achieved for thepulverized coal with a small flow rate of oxygen-enriched flow. The HTOEC modelburner has excellent performance in flame stabilization, fuel flexibility, assisted-oilsaving and low NO_xemission, and thus has a great potential for industrial application. 3) The numerical simulation results showed that under the high temperature andoxygen-enriched conditions, the flame temperature and combustion intensity of thepulverized coal jet increases, and the release rate of the volatile matter rises. With asmall flow rate of oxygen-enriched flow, consistent with the experimental results, NO_xemission could be remarkably reduced. NO_xemission first decreases and then increaseswith the oxygen concentration in the oxygen-enriched air flow, and the turning pointhappens at about50%.4) With the consideration of the intermediate reactions of the volatile matter andthe adoption of the extinction theory developed by Magnussen, the perdition accuracyof the EDC model increases in simulating the turbulent pulverized coal combustion.Combining the EDC model with the skeletal mechanizing and the traditional postprocessing method, and correction of the experimental data, NO_xemission of theturbulent pulverized coal combustion can be predicted with an acceptable accuracy.Dividing the computational domain into a core reaction zone and a non-core zone andlimiting the complex chemistry in the core reaction zone can effectively save the CPUcost and thus allow the industrial application for the modified EDC model with higheraccuracy.更多还原