全预混紧凑缝隙式水冷燃气锅炉燃烧特性模拟

doi:10.16085/j.issn.1000-6613.2023-1312

摘要/Abstract

摘要：

为解决传统燃气锅炉污染物排放量高、体积大等问题，研发了一种全预混冷凝式燃气锅炉，采用并排的水冷板翅插合形成燃烧器头部及冷凝换热段，二者之间设为炉膛，锅炉本体采用挤压铝工艺一体化成型，结构紧凑、换热能力强、耐腐蚀、工艺简单、成本低。由于模型对称，对其基础单元的流场、温度场、火焰长度及污染物排放特性进行数值模拟研究，并通过燃烧实验对模拟结果进行验证。结果表明，该燃气锅炉在12~24kW的热负荷范围内流场均匀，易于点火和稳定燃烧。钝体与火孔出口之间的距离为4mm、钝体宽度为1.0mm、过量空气系数为1.2、燃烧室长度为120mm，满负荷24kW燃烧时，锅炉排放的NO _x <95mg/m³，CO<50mg/m³，锅炉本体尺寸仅为229mm×251mm×60mm，实现了燃气锅炉的超紧凑低排放，对全预混水冷燃气锅炉的节能减排及低碳设计、改造具有重要的现实指导意义。

关键词: 全预混, 水冷, 燃气燃烧, 节能减排, 低碳

Abstract:

To solve the problems of high pollutant emission and large volume of traditional gas boilers, a fully premixed condensing gas boiler was developed. The boiler adopted side-by-side water-cooling plate fins inserted to form the burner head and the condensing heat exchange section. The furnace was between the burner head and the condensing heat exchange section. The boiler body was produced by extrusion aluminum process, with compact structure, strong heat transfer ability, corrosion resistance, simple process and low cost. Due to the symmetry of the model, the flow field, temperature field, flame length and pollutant emission characteristics of the basic unit were studied by numerical simulation. And the simulation results were verified by the combustion experiment. The results indicate that the boiler has a uniform flow field in the load range of 12—24kW. It is easy to ignite and burn stably. When the distance between the blunt body and the outlet of the fire hole is 4mm, the width of the blunt body is 1.0mm, the excess air coefficient is 1.2 and the combustion chamber length is 120mm, the NO _x emissions are less than 95mg/m³ and the CO emissions are less than 50mg/m³ at the full load of 24kW. The size of the boiler body is only 229mm×251mm×60mm. The boiler achieves ultra-compact and low emissions, which has important practical guiding significance for energy saving, emission reduction and low-carbon design as well as transformation of fully premixed water-cooling gas boiler.

Key words: fully premixed, water-cooling, gas combustion, energy conservation and emission reduction, low carbon

中图分类号:

TK16

王宁, 邓世丰, 曲腾, 邵怀爽, 赵钦新. 全预混紧凑缝隙式水冷燃气锅炉燃烧特性模拟[J]. 化工进展, 2024, 43(9): 4871-4881.

WANG Ning, DENG Shifeng, QU Teng, SHAO Huaishuang, ZHAO Qinxin. Simulation on combustion characteristics of fully premixed water-cooling gas boiler with compact slit structure[J]. Chemical Industry and Engineering Progress, 2024, 43(9): 4871-4881.

图/表 27

图1 新型燃气锅炉本体结构

图2 基础单元结构及特征位置

图3 流动模型网格无关性验证

图4 网格分布

图5 燃烧特性模拟的物理模型及局部网格

图6 燃烧模型网格无关性验证

表1 燃烧模型入口边界条件设置

过量空气系数（α）	CH₄摩尔分数	O₂摩尔分数	N₂摩尔分数	气体温度/K	入口速度/m∙s^-1
过量空气系数（α）	CH₄摩尔分数	O₂摩尔分数	N₂摩尔分数	气体温度/K	24kW	12kW	6kW
1.1	0.087169	0.191771	0.721060	300	2.720	1.360	0.680
1.2	0.080489	0.193175	0.726336	300	2.950	1.475	0.738
1.3	0.074761	0.194378	0.730861	300	3.175	1.588	0.794

表2 燃烧模型温度边界条件设置

编号	边界名称	边界类别	温度/K
1	混合气入口	velocity-inlet	300
2	火孔壁面	wall-temperature	333
3	流体对称面	symmetry	—
4	钝体壁面	wall-temperature	500^[12]
5	换热器壁面	wall-temperature	323
6	烟气出口	outflow	300

图7 实验系统及实验平台

图8 计算模型验证

图9 中轴线A上的轴向速度分布

图10 不同热负荷中间面S上流线图

图11 钝体结构参数

图12 不同钝体与火孔出口之间的距离中间面S上的流线分布（Ld=2.0mm）

图13 中轴线A上流体轴向速度分布

图14 钝体出口流体速度分布

图15 不同Ld时钝体出口处速度分布

图16 甲烷质量分数分布云图

图17 温度分布云图

图18 燃烧室最高温度变化

图19 NO质量分数分布云图

图20 NO x 排放量随过量空气系数的变化

图21 CO质量分数分布云图

图22 CO排放量随过量空气系数的变化

图23 甲烷质量分数分布云图

图24 Q=24kW、α=1.2时燃烧特性变化

图25 中轴线上CO质量分数变化

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