Influence of Displacement Ventilation on Local Exhaust Ventilation and Analysis of Ventilation Efficiency

doi:10.12068/j.issn.1005-3026.2025.20240066

Abstract

Abstract:

The method of coupling displacement ventilation and mobile local exhaust ventilation can improve the control effect of welding fume generated at non-fixed points in a large-space workshop， but the influence of ventilation parameters on the control effect still needs to be clarified. The effects of air supply velocity and angle during displacement ventilation on the fume capture efficiency of the local exhaust hood were explored when parameters such as distance between local exhaust hood opening and welding point， air velocity at hood opening， and relative position between welding point and air supply outlet during displacement ventilation changed， and the coupled ventilation efficiency was analyzed. The results show that when the air supply angle is 0° （horizontal）， a higher air supply velocity during displacement ventilation has a greater impact on the local exhaust ventilation. A higher air supply velocity at the local exhaust hood opening and a closer distance from the hood opening to the welding point mean that its fume capture efficiency is less affected by displacement ventilation. A closer distance from the welding point to the air supply outlet during displacement ventilation indicates a greater impact of displacement ventilation on local exhaust ventilation. Increasing the air supply angle can weaken the impact. The efficiency of coupled ventilation is higher than that of single displacement ventilation， which can be stabilized to 80% within 15 min. Research results can provide a basis for the design and management of the coupled ventilation system.

Key words: fume control, displacement ventilation, local exhaust ventilation, coupled ventilation, ventilation efficiency

CLC Number:

X 962

Xiu-li LIN, Yu-hong ZHOU, Jing-xian LIU. Influence of Displacement Ventilation on Local Exhaust Ventilation and Analysis of Ventilation Efficiency[J]. Journal of Northeastern University(Natural Science), 2025, 46(10): 113-122.

Figures/Tables 19

Fig.1 Schematic diagram of coupling principle between displacement ventilation and local exhaust ventilation

Fig.2 Geometric model of workshop

Table 1 Boundary conditions and parameters setting

区域	边界类型	边界参数设置
		速度	温度	离散相
		m·s^-1	K	离散相
置换送风口	速度入口	0.5, 1.0, 1.5, 2.0	300	逃逸
回风口	自由出口	—	—	逃逸
排风罩抽风口	速度入口	15, 20, 25	300	逃逸
排风罩罩口	内部界面	—	—	—
焊接热源	速度入口	0.5	1 500	逃逸
其他壁面	壁面	—	—	捕集

Fig.3 Mesh dividing

Fig.4 Mesh independence test

Fig.5 Schematic diagram of field measurement point arrangement

Fig.6 Simulation validity verification

Fig.7 Ventilation efficiency of workshop under different air supply velocities

Fig.8 Cloud map of fume concentration distribution in Y=6 m plane under different air supply velocities

Fig.9 Fume concentration distribution in monitoring line under different air supply velocities

Fig.10 Influence of distance between hood opening and pollution source on efficiency of local exhaust hood

Fig.11 Influence of air supply velocity at hood opening on efficiency of local exhaust hood

Fig.12 Influence of longitudinal position of solder station on efficiency of local exhaust hood

Fig.13 Influence of lateral position of solder station on efficiency of local exhaust hood

Fig.14 Influence of air supply angle on efficiency of local exhaust hood

Table 2 Cases setting

工况	置换风速/(m·s^-1)	排风罩抽风口风速/(m·s^-1)	送风角度/(°)
1	0.5	25	75
2	1.0	25	75
3	1.5	25	75
4	2.0	25	75

Fig.15 Coupled ventilation efficiency of workshop under different cases

Fig.16 Cloud map of fume concentration distribution in Y=6 m plane under different cases

Fig.17 Fume concentration distribution in monitoring line under different cases

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