喷淋对大空间喷头上方羽流特性的影响

基于经典羽流模型,通过全尺寸试验测量大空间喷头上方羽流中心线不同高度处的温度和速度,分析羽流中心线温度和速度的变化规律,并与经典羽流模型做比较,得出喷淋对大空间喷头上方羽流特性的影响。结果表明:喷淋启动前,羽流温度和速度随高度增加的变化趋势与经典羽流模型基本一致;喷淋启动后,各高度处温度显著降低,速度显著减小,温度随时间的变化趋势与喷淋压力有关,且温度和速度随高度增加的变化趋势发生明显改变。

Effect of sprinkling on the behaviors of the plume over the sprinkler in a large space building

The paper was intended to make an investigation of the effects of the sprinkling behavior on the characteristic features of the plume over the sprinkler in a large space building.For this purpose,full-scale burning tests were conducted.The temperature and velocity of the plume at the different heights above the sprinkler in the central line of the plume were measured in accordance with the demands of the classic plume model.The results of tests showed that:(1) Before the sprinkler began to activate,the plume temperature and velocity tended to change with its assembling height mainly in accordance with the plume's classical model,that was to say,the temperature and velocity tended to decrease with the increase of its assembling height.However,there existed some gap between the experimental data we had gained and the data given by the theoretical model,which might imply that the plume in a large space building was likely to fail to rise to the height of the ceiling,rather,the plume might accumulate itself within the interior space of the building;(2) After the sprinkler began to work,the plume temperature and velocity would soon reduce sharply.The temperature change would be affected by the spray pressure.Under the low spray pressure,the temperature tended to keep increasing for some time,but at the high spray pressure,it tended to decrease or remain stable.The plume velocity kept stable when pressure changed,it was little affected by spray pressure;(3)When the sprinkler began to work,the plume temperature and velocity tended to keep on changing with its height in a remarkable different way as compared that without sprinkler:The difference of the temperature reduced with the height along the plume central line,which would make the plume less rising activity.So the plume would be more difficult to rise and then the smoke would spread more crosswise.This would lead to the smoke difficult to exhaust and easy to fall.Then the evacuation would be affected obviously;(4) The temperature and velocity of the plume would be affected by the fire heat release rate.Either before or after the sprinkler was activated,the plume temperature and velocity at each height would increase with the increase of the fire source.