蒸汽稀释天然气扩散火焰燃烧特性研究

发布时间：2018-07-17 21:42

【摘要】：国内燃机电厂普遍存在启动过程、低负荷工况下冒黄烟的问题,值班扩散火焰污染物排放高是主因。蒸汽稀释降低值班火焰污染物排放是一种可行的解决途径。本文从零维分析入手,研究了蒸汽稀释比和稀释均匀性对天然气扩散火焰污染物生成的影响;采用三维模拟分析手段参数化研究了天然气/蒸汽混合装置关键结构影响;最后,基于某值班扩散燃烧器,实验研究了蒸汽稀释天然气扩散燃烧的火焰结构、污染物生成等特性。本论文主要工作如下:(1)基于CHEMKIN软件平台构建了化学反应网络模型,建立了天然气/蒸汽掺混不均匀度(Spatial Mixing Defficiency,SMD)模型,采用零维模拟手段定性分析了蒸汽稀释比和稀释SMD对CO、NOx生成的影响规律。结果表明,随蒸汽稀释比增加,NOx生成受到抑制,而CO生成增加;相同蒸汽稀释比下,随蒸汽稀释SMD增加,CO、NOx生成均呈增加趋势,结果体现了改善天然气/蒸汽掺混均匀性能的重要性。(2)针对天然气和蒸汽的掺混装置,选用SV静态混合器结构形式,数值模拟分析了混合单元数、混合单元倾角及混合单元间间隙对掺混性能的影响。确定了静态混合器优选结构方案:混合单元数5,混合单元叶片倾角45°,混合单元间无间隙。(3)针对某应用于燃气轮机燃烧室的值班扩散喷嘴,采用数值模拟结合实验研究的方法,研究了蒸汽稀释比和稀释均匀性对扩散火焰特性和污染物排放的影响。结果表明,随稀释比增加,天然气扩散火焰OH强度变弱,火焰结构趋于紧凑,CO增加、NOx降低,但随稀释比进一步增加,NOx减排收益降低,且火焰稳定性下降;相同蒸汽稀释比下,通过静态混合器降低蒸汽稀释SMD后,扩散火焰结构近似无变化,但反应区OH峰值信号强度减弱,NOx、CO均呈下降趋势。实验结果验证了改善蒸汽稀释均匀性对值班扩散火焰减排的有效性。本研究结果可为天然气燃气轮机解决启动过程中冒黄烟问题、拓宽低NOx工况范围提供理论依据和实验数据参考。
[Abstract]:The problem of yellow smoke emission under low load condition and high pollutant emission from duty diffusion flame are the main causes of the start-up process in the power plants of internal combustion engine in China. Steam dilution is a feasible way to reduce the discharge of flame pollutants on duty. In this paper, the effects of steam dilution ratio and dilution uniformity on the formation of natural gas diffusion flame pollutants are studied, and the key structure of natural gas / steam mixing unit is parameterized by means of three-dimensional simulation analysis. Based on a duty diffusion burner, the flame structure and pollutant formation of steam diluted natural gas diffusion combustion were studied experimentally. The main work of this thesis is as follows: (1) based on the CHEMKIN software platform, the chemical reaction network model is constructed, and the spatial mixing efficiency SMD model is established. The effects of steam dilution ratio and diluted SMD on the formation of COO _ (no _ x) were qualitatively analyzed by means of zero dimensional simulation. The results showed that the formation of no _ x was inhibited with the increase of steam dilution ratio, and the formation of CO _ x increased with the increase of SMD at the same steam dilution ratio, and the formation of CO _ (no _ x) increased with the increase of SMD. The results show the importance of improving the homogeneity of natural gas / steam mixing. (2) for the mixing device of natural gas and steam, SV static mixer is selected and the number of mixing units is numerically simulated. The influence of the mixing angle and the gap between the mixing units on the mixing performance. The optimal structure scheme of static mixer is determined: the number of mixing units is 5, the blade inclination angle of mixing unit is 45 掳, and there is no gap between the mixing units. (3) for a duty diffusion nozzle used in a gas turbine combustor, a numerical simulation method combined with experimental study is adopted. The effects of steam dilution ratio and dilution uniformity on diffusion flame characteristics and pollutant emission were studied. The results show that with the increase of dilution ratio, the OH intensity of natural gas diffusion flame becomes weaker, the flame structure tends to be compact and CO increases and no _ x decreases, but with the increase of dilution ratio, the emission reduction income of no _ x decreases, and the flame stability decreases, and at the same steam dilution ratio, When the SMD was reduced by static mixer, the diffusion flame structure was almost unchanged, but the peak signal intensity of OH in the reaction region decreased and no _ x _ (10) CO decreased. The experimental results demonstrate the effectiveness of improving the uniformity of steam dilution on duty diffusion flame emission reduction. The results of this study can provide theoretical basis and experimental data reference for natural gas turbine to solve the problem of yellow smoke during start-up and to widen the range of low no _ x working conditions.
【学位授予单位】：中国科学院大学(中国科学院工程热物理研究所)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM621;TK471

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