乙醇浓度和应变率对扩散火焰特性的数值分析

doi:10.11949/0438-1157.20201376

摘要/Abstract

摘要：

研究液体燃料乙醇对冲燃烧的火焰特性是理解扩散火焰形成和指导乙醇对冲燃烧器设计的关键。采用对冲扩散火焰模型，结合光学薄辐射模型，模拟空气与氮气稀释下乙醇形成的扩散火焰，探讨了乙醇浓度和应变率对扩散火焰的火焰结构、温度分布和温度峰值处的温度敏感性的影响规律。结果表明：随着乙醇浓度的增加，CO和H₂反应区域向燃料侧移动，火焰区域变宽，火焰温度峰值逐渐升高，升高趋势渐缓，中间产物和CO对温度敏感性的影响减弱；随着应变率的增加，自由基和CO增多，中间产物减少，组分的分布区域和火焰区域变窄，火焰温度峰值逐渐降低，中间产物和CO对温度敏感性的影响逐渐增强。

关键词: 燃料, 乙醇, 对冲火焰, 火焰特性, 应变率, 数值分析

Abstract:

Analysis on the flame characteristics of ethanol counter flame combustion is the key to understand the formation of diffusion flame and guide the design of ethanol counter flame burners. The combustion characteristics of the diffusion flame of ethanol diluted with air and nitrogen are simulated by using the counter flame diffusion flame model combined with the optical thin radiation model, and the influences of ethanol concentration and strain rate on the flame structure, temperature distribution and temperature sensitivity of the peak temperature location are discussed. The results show that with the increase of ethanol concentration, the CO and H₂ reaction zone moves to the fuel side, the flame area becomes wider, the peak flame temperature gradually increases, and the rising trend gradually slows down, and the influence of intermediate products and CO on temperature sensitivity decreases. With the increase of strain rate, free radicals and CO increase, intermediate products decrease, component distribution area and flame area become narrower, flame temperature peak gradually decreases, and the influence of intermediate products and CO on temperature sensitivity gradually increases.

Key words: fuel, ethanol, counter flame, flame characteristics, strain rate, numerical analysis

中图分类号:

TK 16

石敦峰, 甘云华, 罗燕来, 江政纬, 周毅. 乙醇浓度和应变率对扩散火焰特性的数值分析[J]. 化工学报, 2021, 72(5): 2801-2809.

SHI Dunfeng, GAN Yunhua, LUO Yanlai, JIANG Zhengwei, ZHOU Yi. Numerical analysis of ethanol concentration and strain rate on diffusion flame characteristics[J]. CIESC Journal, 2021, 72(5): 2801-2809.

图/表 11

图1 火焰结构示意图

Fig.1 Schematic diagram of flame structure

表1 模拟工况（TF=360 K，TO=298 K，P=0.1 MPa）

Table 1 Simulation conditions（TF=360 K，TO=298 K，P=0.1 MPa）

工况	燃料侧u_F/(cm·s^-1)	氧化剂侧u_O/(cm·s^-1)	当量比Φ	摩尔分数		应变率a/s^-1
工况	燃料侧u_F/(cm·s^-1)	氧化剂侧u_O/(cm·s^-1)	当量比Φ	乙醇	氮气	应变率a/s^-1
1	11.18	10.50	1.32	0.15	0.85	30
2	11.02	10.50	1.74	0.20	0.80	30
3	10.87	10.50	2.14	0.25	0.75	30
4	10.18	10.50	4.01	0.50	0.50	30
5	9.61	10.50	5.68	0.75	0.25	30
6	9.13	10.50	7.20	1.00	0.00	30
7	21.74	21.00	2.14	0.25	0.75	60
8	32.61	31.50	2.14	0.25	0.75	90

图2 火焰温度的实验与仿真对比

Fig.2 The comparison between experimental and simulated results of flame temperature

图3 扩散火焰的温度、热释放率和组分的分布（XF=0.25,a=30 s-1）

Fig.3 The distributions of temperature, heat release rate and component of diffusion flame (XF=0.25,a=30 s-1)

图4 扩散火焰的温度、热释放率和组分的分布（XF=0.75, a=30 s-1）

Fig.4 The distributions of temperature, heat release rate and component of diffusion flame (XF=0.75,a=30 s-1)

图5 扩散火焰的温度、热释放率和组分的分布（XF=0.25, a=90 s-1）

Fig.5 The distributions of temperature, heat release rate and component of diffusion flame (XF=0.25,a=90 s-1)

图6 乙醇浓度对温度分布和热释放率的影响（a=30 s-1）

Fig.6 The influence of ethanol concentration on temperature distribution and heat release rate (a=30 s-1)

图7 应变率对温度分布和热释放率的影响（XF=0.25）

Fig.7 The influence of strain rate on temperature distribution and heat release rate (XF=0.25)

图8 乙醇浓度和应变率对火焰温度峰值的共同影响

Fig.8 The effects of ethanol concentration and strain rate on the peak flame temperature

图9 温度峰值点处的乙醇浓度对温度敏感系数的影响（a=30 s-1）

Fig.9 The influence of ethanol concentration on the temperature sensitivity coefficient at the peak temperature point (a=30 s-1)

图10 温度峰值点处的应变率对温度敏感系数的影响（XF=0.25）

Fig.10 The influence of strain rate on temperature sensitivity coefficient at the temperature peak point (XF=0.25)

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