Effect of methane explosion on distribution of pressure field inside and outside buildings

doi:10.11949/0438-1157.20200064

Abstract

Abstract:

Premixed methane gas explosions caused by leaked natural gas pose a serious threat to the lives, which may lead to casualties and buildings collapse. So it is important to know the distribution of pressure fields around buildings when there is an explosion. Then people can escape to a relative safe place. Based on the Fluent software, a calculation model suitable for the overpressure of the unconstrained explosion of methane was established, and it was corrected by experimental data. The results show that highest accuracy appears in the SAS turbulence model and the Laminar Finite-Rate model when there is no object to limit the explosion, and that the volume of methane air mixture involved in combustion explosion at the stoichiometric concentration is about 1/3 of the total volume. Then a model for methane unconfined explosion is established. The influence of building height and width on the pressure field is analyzed. Furthermore, the distribution of pressure field inside the building is studied. And the results show that the middle-upper part of buildings is safer than the bottom when the building does not fail. The width of a building affects its resistance to positive overpressure. But neither the height nor the width of the building will affect the change of negative overpressure. Thus in the emergency explosion accidents, it will more vulnerable to the strong impact of positive and negative overpressure that escaping to the bottom blindly.

Key words: explosions, safety, model, pressure field, numerical simulation

摘要：

天然气泄漏导致的预混爆炸，会严重威胁周围人员的生命及财产安全，因此掌握气体预混爆炸在建筑物周围产生压力场的分布至关重要。基于Fluent软件，建立了适用于甲烷无约束爆炸超压的计算模型，并通过实验数据对其修正，结果表明：在化学计量浓度下参与燃烧爆炸的预混气体体积约为总体积的1/3，即当量体积。在此基础上建立了适用于甲烷约束爆炸的仿真模型，分析了建筑物高度和宽度对建筑周围压力场的影响，并进一步研究了气体爆炸对建筑物内部压力场分布的影响。结果表明，在建筑物不失效前提下，背对爆炸源一侧中上部为较安全区域，在紧急爆炸事故中，盲目的向下逃生，反而容易受到爆炸超压的强烈冲击。

关键词: 爆炸, 安全, 模型, 压力场, 数值模拟

CLC Number:

TH 88

Yuxing LI,Yuanbo YIN,Yazhen WANG,Cuiwei LIU. Effect of methane explosion on distribution of pressure field inside and outside buildings[J]. CIESC Journal, 2020, 71(11): 5337-5351.

李玉星,尹渊博,王雅真,刘翠伟. 甲烷爆炸对建筑物内外压力场分布的影响[J]. 化工学报, 2020, 71(11): 5337-5351.

Figures/Tables 30

Table 1 Damage effect of shock wave overpressure on human body

超压 $Δ p$ /MPa	伤害作用
0.02~0.03	轻微损伤
0.03~0.05	听觉器官损伤或骨折
0.05~0.10	内脏严重损伤或死亡
>0.10	大部分人员死亡

Table 1 Damage effect of shock wave overpressure on human body

超压 $Δ p$ /MPa	伤害作用
0.02~0.03	轻微损伤
0.03~0.05	听觉器官损伤或骨折
0.05~0.10	内脏严重损伤或死亡
>0.10	大部分人员死亡

Table 2 Damage effect of shock wave overpressure on buildings

超压 $Δ p$ /MPa	破坏作用
0.005~0.006	门窗玻璃部分破碎
0.006~0.015	受压面门窗不玻璃破碎
0.015~0.02	窗框损坏
0.02~0.03	墙裂缝
0.04~0.05	墙大裂缝，屋瓦掉下
0.06~0.07	木建筑房柱折断、松动
0.07~0.10	砖墙倒塌
0.10~0.20	防震钢筋混泥土破坏，小房屋倒塌
0.20~0.30	大型钢架结构破坏

Table 2 Damage effect of shock wave overpressure on buildings

超压 $Δ p$ /MPa	破坏作用
0.005~0.006	门窗玻璃部分破碎
0.006~0.015	受压面门窗不玻璃破碎
0.015~0.02	窗框损坏
0.02~0.03	墙裂缝
0.04~0.05	墙大裂缝，屋瓦掉下
0.06~0.07	木建筑房柱折断、松动
0.07~0.10	砖墙倒塌
0.10~0.20	防震钢筋混泥土破坏，小房屋倒塌
0.20~0.30	大型钢架结构破坏

Table3 Grid information

编号	不同区域网格大小	网格数
1^#	点火区0.01 m×0.01 m，可燃物区0.04 m×0.04 m，空气区0.2 m×0.2 m	23150
2^#	点火区0.005 m×0.005 m，可燃物区0.02 m×0.02 m，空气区0.1 m×0.1 m	45044
3^#	点火区0.0025 m×0.0025 m，可燃物区0.01 m×0.01 m，空气区0.05 m×0.05 m	65103

Fig.1 Sensitivity analysis of grid

Fig.2 Schematic diagram of unconstrained explosion model grid

Table 4 Comparison of peak overpressure and arrival time of different turbulence models

湍流模型	峰值超压ΔP/Pa	到达时间/s
SAS	578.87	0.19
k-ε standard	1020.3	0.07
k-ε RNG	不收敛
k-ε realizable	805.34	0.11
k- $ω$ standard	点火未成功
k- $ω$ SST	1684.7	0.16

Table 4 Comparison of peak overpressure and arrival time of different turbulence models

湍流模型	峰值超压ΔP/Pa	到达时间/s
SAS	578.87	0.19
k-ε standard	1020.3	0.07
k-ε RNG	不收敛
k-ε realizable	805.34	0.11
k- $ω$ standard	点火未成功
k- $ω$ SST	1684.7	0.16

Table 5 Effect of ignition energy on explosion overpressure

球体点火区域半径/m	等价点火能/mJ	爆炸峰值超压ΔP/Pa
0.004	100	578.87
0.006	350	582.15
0.008	830	583.67
0.01	1600	580.45

Table 6 Explosion conditions of different volume cubic premixed gases

工况编号	预混立方体边长a/m	甲烷体积浓度/%	监测体积范围/(m×m)	点火方式
1	1	9.5	20×15	中心点火
2	2	9.5	20×15	中心点火
3	3	9.5	20×15	中心点火

Fig.3 Diagram of experimental equipment

Fig.4 Experimental results for unconstrained methane/air premixed explosions in different mixture volumes and different detection distances

Fig.5 Schematic diagram of unconstrained explosion

Fig.6 Fluent numerical simulation results of 2 m unconstrained premixed cubic gas explosion

Fig.7 Methane volume concentration distribution of case 2 m

Table 7 The positive and negative overpressure original Fluent simulation results and experimental data

预混气云边长/m	监测点位置/m	正超压/Pa			负超压/Pa
预混气云边长/m	监测点位置/m	模拟值	实验值	比值	模拟值	实验值	比值
1	2	252.93	108.62	2.33	-180.75	-64.66	2.80
	2.5	203.34	88.21	2.31	-128.64	-47.16	2.73
	3	165.57	69.13	2.40	-112.26	-45.65	2.46
2	2	555.72	173.28	3.21	-436.62	-137.07	3.19
	2.5	508.08	147.16	3.45	-362.61	-119.21	3.04
	3	411.36	140.43	2.93	-295.29	-103.04	2.87
3	2	894.93	276.72	3.23	-714.45	-212.06	3.37
	2.5	763.65	241.05	3.17	-567.99	-178.17	3.19
	3	680.22	223.91	3.04	-437.85	-144.78	3.02

Fig.8 Schematic diagram of obstacle arrangement (a) and meshing(b)

Fig.9 Schematic diagram of monitoring point

Table 8 Obstacle research conditions setting table

分组研究	工况编号	障碍物高度h/m	障碍物宽度b/m	障碍物到爆心距离d/m	监测体积范围/m×m×m
A组：障碍物高度研究	A-1	2	2	2	20×20×15
	A-2	3	2	2	20×20×15
	A-3	4	2	2	20×20×15
	A-4	5	2	2	20×20×15
	A-5	6	2	2	20×20×15
B组：障碍物宽度研究	B-1	4	1	2	20×20×15
	B-2	4	2	2	20×20×15
	B-3	4	3	2	20×20×15
	B-4	4	4	2	20×20×15
	B-5	4	5	2	20×20×15

Fig.10 Pressure distribution of XZ plane passing through the ignition point at different times for case A-3

Fig.11 Overpressure distribution on the facing surface of obstacles of case group A

Fig.12 Overpressure distribution on the back surface of obstacles of case group A

Fig.13 Pressure fields at maximum positive overpressure corresponding time for case group B

Fig.14 Pressure fields at maximum negative overpressure corresponding time for case group B

Fig.15 Overpressure distribution on the facing surface of obstacles of case group B

Fig.16 Overpressure distribution on the back surface of obstacles of case group B

Fig.17 The monitor points arrangement in obstacle

Table 9 Maximum overpressure comparison between case A-3 and case C

工况编号	ΔP_max+/Pa	ΔP_max-/Pa
A-3	253.04	-196.93
C	251.51	-164.02

Fig.18 Overpressure distribution on the facing surface of obstacles for case A-3 and case C

Fig.19 Overpressure distribution on the back surface of obstacles for case A-3 and case C

Fig.20 Overpressure change diagram inside the obstacle on z=2 m height

Fig.21 Overpressure changes with height on the inner axis of the obstacle

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