Analysis of velocity and concentration field characteristics of heavy gas leakage in large space

doi:10.11949/0438-1157.20191163

Abstract

Abstract:

In the real industrial plants, the equipments are often critical to the contaminant dispersion and distribution. The leakage position on both sides of the obstacle has been taken into consideration. Gravity intensity index, dimensionless concentration, and the proportion of flammable and explosive area have been defined. The accuracy of the computational fluid dynamics (CFD) model was verified by experiments, and the velocity field and concentration field of different pollutant release rates were calculated by CFD. The calculation results show that the structure of the velocity field and the distribution pattern of the concentration field change with the increase of the pollutant release rate. When the dimensionless number θ_inlet exceeds 0.0288, new eddy currents will appear near the pollution source, and the dimensionless concentration distribution begins to appear vertical stratification. When the contaminant volumetric release rate exceeds 2.66667×10^-5 m³/s, the size of the flammable, explosive and explosive areas becomes significant, leading to potential explosion risks.

Key words: fluid mechanics, heavy gas, experimental validation, velocity field, concentration field, explosion

摘要：

在实际的工业场景中，机器设备等障碍物的存在对污染物的扩散及分布有着很重要的影响。考虑了在有障碍物的大空间中，泄漏位置在障碍物两侧的场景。定义了污染源重力作用强度指标、无量纲浓度以及易燃易爆区域占比。用实验验证了计算流体力学（CFD）模型的准确性，进而用CFD计算了不同污染物释放速率时的速度场及浓度场。计算结果表明，随着污染物释放速率的增加，速度场的结构和浓度场的分布形式都发生变化。当无量纲数θ_inlet超过0.0288时，污染源附近会出现新的涡流，而无量纲浓度分布开始出现垂直分层的趋势。当污染源体积释放速率超过2.66667×10^-5 m³/s时易燃易爆区域的大小变得显著，导致潜在的爆炸风险。

关键词: 流体力学, 重气, 实验验证, 速度场, 浓度场, 爆炸

CLC Number:

TQ 028.8

Qianru ZHANG, Xu ZHANG, Wei YE, Chengqiang ZHI, Yixiang HUANG, Wenxuan ZHAO, Jun GAO. Analysis of velocity and concentration field characteristics of heavy gas leakage in large space[J]. CIESC Journal, 2020, 71(S1): 57-67.

张倩茹, 张旭, 叶蔚, 职承强, 黄奕翔, 赵文萱, 高军. 大空间重气泄漏下速度场、浓度场特性分析[J]. 化工学报, 2020, 71(S1): 57-67.

Figures/Tables 19

Fig.1 Model constructed in Geometry Modeler

Table 1 Simulation configurations

工况名称	换气次数/h^-1	污染源位置/m	污染源释放强度/ （kg/(m³·s)）
A1	3	(0，4，0.5)	1
A2	3	(0，4，0.5)	5
A3	3	(0，4，0.5)	10
A4	3	(0，4，0.5)	20
A5	3	(0，4，0.5)	50
B1	3	(0，2，0.5)	1
B2	3	(0，2，0.5)	5
B3	3	(0，2，0.5)	10
B4	3	(0，2，0.5)	20
B5	3	(0，2，0.5)	50

Table 2 θinlet values for each contaminant release rate

污染源释放强度/(kg/(m³·s))	θ_inlet
1	0.0106
5	0.0181
10	0.0228
20	0.0288
50	0.0390

Fig.2 Large space chamber

Fig.3 Obstacle and contaminant source in experiments

Fig.4 Measurement points

Fig.5 Concentration validation

Fig.6 Velocity magnitude contours and streamlines on Z=0.5 m plane without contaminant source

Fig.8 Velocity magnitude contours and streamlines on symmetry plane without contaminant source

Fig.7 Velocity magnitude contours and streamlines on Z=0.2 m plane without contaminant source

Fig.9 Velocity magnitude contours and streamlines on Z=0.5 m plane when contaminant source is at A(0, 4 m, 0.5 m)

Fig.11 Velocity magnitude contours and streamlines on symmetry plane when contaminant source is at A(0, 4 m, 0.5 m)

Fig.10 Velocity magnitude contours and streamlines on Z=0.2 m plane when contaminant source is at A(0, 4 m, 0.5 m)

Fig.12 Velocity magnitude contours and streamlines on Z=0.5 m plane when contaminant source is at B(0, 2 m, 0.5 m)

Fig.13 Velocity magnitude contours and streamlines on Z=0.2 m plane when contaminant source is at B(0, 2 m, 0.5 m)

Fig.14 Velocity magnitude contours and streamlines on symmetry plane when contaminant source is at B(0, 2 m, 0.5 m)

Fig.15 Dimensionless concentration contours on symmetry plane when contaminant source is at A(0, 4m, 0.5m)

Fig.16 Dimensionless concentration contours on symmetry plane when contaminant source is at B(0, 2 m, 0.5 m)

Fig.17 Change of proportion of flammable and explosive area with contaminant gas volumetric rate

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