气固射流扩散火焰形态研究

doi:10.11949/0438-1157.20201426

摘要/Abstract

摘要：

利用文丘里效应，自行设计气固射流扩散火焰（气固喷射火）实验装置，分别采用147 μm和178 μm两种粒径均匀的白色石英砂以近似恒定速率卷吸入火焰中，来研究固体颗粒对火焰形态的影响，特别地，通过关闭侧面进砂口所形成的气态射流扩散火焰（气态喷射火）与之相比较。理论分析和实验结果表明，砂子进入火焰中会降低火焰温度，并且粒径为147 μm的砂子进入火焰的质量大于178 μm砂子，导致小粒径气固喷射火具有更低的火焰温度，从而具有更低的层流燃烧速度和更大的火焰Froude数，最终使其具有更高的推举高度和火焰高度。对比分析气固喷射火和气态喷射火实验结果，也表明固体颗粒对火焰温度的冷却作用导致气固喷射火更容易产生推举现象并具有更高的火焰高度。

关键词: 气固混合物, 喷射火, 火焰温度, 火焰高度, 推举高度

Abstract:

This study investigates the flame geometrical features of the gas-solid jet diffusion flame (GSJDF). A new facility is designed and built using the Venturi effect, by which the jet diffusion flame can entrain the micron-sized solid particles at constantrate. The uniform white quartz sands of 147 μm and 178 μm in diameters were used for test, respectively. In particular, the gas jet diffusion flame (gas jet fire) formed by closing the side sand inlet is compared with it. Theoretical analysis and experimental result make sense that the addition of sand reduces the flame temperature, and then increases the flame height and the lift-off height by increasing the flame Froude number and decreasing the flame burning speed, respectively. The GSJDF of 147 μm sand has a higher flame height and lift-off height than that of 178 μm sand, for the total mass of 147 μm sand entrained into the flame is larger and so leads to a less flame temperature. In addition, the GSJDF holds a larger trend to produce the lift-off phenomena and a higher flame height than the jet diffusion flame, which also indicates the role of sand in the flame temperature reduction.

Key words: gas-solid mixtures, jet diffusion flame, flame temperature, lift-off height, flame height

中图分类号:

X 931

聂璇, 周魁斌, 吴月琼, 黄梦源, 蒋军成. 气固射流扩散火焰形态研究[J]. 化工学报, 2021, 72(5): 2878-2886.

NIE Xuan, ZHOU Kuibin, WU Yueqiong, HUANG Mengyuan, JIANG Juncheng. Study on the flame shape of gas-solid jet diffusion[J]. CIESC Journal, 2021, 72(5): 2878-2886.

图/表 13

图1 气固喷射火装置示意图(a)和砂子卷吸过程示意图(b)

Fig.1 Schematic diagram of the gas-solid jet diffusion flame (a) and sand entrainment process (b)

表1 实验测试工况和数据汇总

Table 1 Test conditions and experimental data summary

$d 0$ /μm	$m c$ /(g/s)	$m s$ /(g/s)	Fr_f	H/m	h/m
0	0.12~0.40	0	0.014~0.045	0.45~0.80	0
147	0.12~0.40	0.11~4.63	0.014~0.053	0.41~1.13	0~0.33
178	0.12~0.40	0.0~5.51	0.014~0.050	0.44~1.05	0~0.25

表1 实验测试工况和数据汇总

Table 1 Test conditions and experimental data summary

$d 0$ /μm	$m c$ /(g/s)	$m s$ /(g/s)	Fr_f	H/m	h/m
0	0.12~0.40	0	0.014~0.045	0.45~0.80	0
147	0.12~0.40	0.11~4.63	0.014~0.053	0.41~1.13	0~0.33
178	0.12~0.40	0.0~5.51	0.014~0.050	0.44~1.05	0~0.25

图2 砂子卷吸速率随气体质量流量变化

Fig.2 Variation of sand entrainment rate with gas mass flow rate

图3 砂子粒径为147 μm时相关参数随时间变化的三次可重复性实验对比

Fig.3 The test repeatability justified by the comparisons of parameters while size of sand is 147 μm

图4 推举高度测量

Fig.4 Schematic of the lift-off height appearance probability contour

图5 粒径为178 μm砂子喷射瞬时图

Fig.5 Instantaneous images showing sand injection with a size of 178 μm

图6 气固喷射火的实验图片

Fig.6 Typical experimental photos of gas-solid jet diffusion flame

图7 气态喷射火火焰的实验图片

Fig.7 Typical experimental photos of gas jet diffusion flame

表2 混合物特性[26]

Table 2 Characteristics of mixture[26]

物质	298 K下生成焓 $h ˉ 0 f$ / (kJ/mol)	比定压热容c_p/(kJ/(kg·K))
CH₄	-103847	—
CO₂	-393546	56.21
H₂O	-241845	43.87
N₂	0	33.71
O₂	0	—

表2 混合物特性[26]

Table 2 Characteristics of mixture[26]

物质	298 K下生成焓 $h ˉ 0 f$ / (kJ/mol)	比定压热容c_p/(kJ/(kg·K))
CH₄	-103847	—
CO₂	-393546	56.21
H₂O	-241845	43.87
N₂	0	33.71
O₂	0	—

表3 用式（7）计算绝热火焰温度与层流火焰传播速度关系

Table 3 The influence of adiabatic flame temperature on laminar flame velocity calculated by Eq. (7)

状况	T_u/K	T_ad,g/K	S_L/S_L,A
A	300	2267	1
B	300	2100	0.69
C	300	2000	0.54
D	300	1900	0.41
E	300	1800	0.31
F	300	1700	0.22

图8 气固混合物喷射火推举高度随丙烷质量流量变化

Fig.8 Variation of lift-off height with propane mass flow rate for gas-solid jet diffusion flame

图9 气固喷射火与气态喷射火火焰高度随丙烷质量流量变化

Fig.9 Variation of flame height with propane flow rate for gas-solid jet diffusion flame and jet diffusion flame

表4 气固喷射火物性参数计算值

Table 4 The calculated physicochemical parameters of gas-solid jet diffusion flame

粒径/μm	m_s/(g/s)	L/m	$L - h L$	m_s,f / (g/s)	u_e,gs/ (m/s)	T_ad,gs/K	Fr_f
147	2.51	0.17	0.12	0.30	1.93	2061	0.033
	3.32	0.31	0.20	0.66	2.46	1930	0.044
	4.09	0.42	0.32	1.31	2.87	1766	0.054
	4.63	0.49	0.34	1.57	3.09	1727	0.059
178	4.97	0.24	0.14	0.69	2.17	1967	0.039
	5.51	0.29	0.16	0.90	2.38	1917	0.043

表4 气固喷射火物性参数计算值

Table 4 The calculated physicochemical parameters of gas-solid jet diffusion flame

粒径/μm	m_s/(g/s)	L/m	$L - h L$	m_s,f / (g/s)	u_e,gs/ (m/s)	T_ad,gs/K	Fr_f
147	2.51	0.17	0.12	0.30	1.93	2061	0.033
	3.32	0.31	0.20	0.66	2.46	1930	0.044
	4.09	0.42	0.32	1.31	2.87	1766	0.054
	4.63	0.49	0.34	1.57	3.09	1727	0.059
178	4.97	0.24	0.14	0.69	2.17	1967	0.039
	5.51	0.29	0.16	0.90	2.38	1917	0.043

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