室内空间重气扩散浓度场变化过程的试验研究

Experimental study on the change of concentration field for leakage and diffusion of the indoor dense gas

以二氧化碳气体为对象,对室内空间重气连续泄漏扩散过程进行试验研究,分析气体体积分数的变化规律。结果表明,二氧化碳在室内空间泄漏后,出现明显的沉降现象,泄漏源高度以下位置的体积分数远大于高处的体积分数,且气体体积分数上升的速度也明显增大。墙壁的阻挡作用会使近墙处气体体积分数比其他位置要高。中心面上,泄漏初期二氧化碳体积分数变化梯度不大,但随着时间的进行,体积分数梯度变大,逐渐出现分层现象。通过比较同一时刻不同面上气体体积分数的分布情况,可以发现,靠近地面处的水平面上体积分数分布较均匀,而垂直面上体积分数分布不均匀。二氧化碳扩散过程中,径向上有一个初始速度,而在横向上表现为自由扩散。不同高度水平面上,随着高度的增加,二氧化碳的体积分数值和高体积分数区域都逐渐减小,且在离泄漏源较远处的两侧墙壁处富集,而泄漏源下方有一个体积分数相对较低的区域。

The paper is to present its author＇s experimental study findings from the continuous leakage and diffusion of carbon dioxide （CO2） inside a room. To do the research, we have built up a rectan- gular testing room （whose size is 3 m× 1.6 m×2.5 m） with CO2 filled up continuously into the interior room space. The CO2 concen- trations at different positions inside the room were measured with an infrared sensor. At the same time, analysis and measurement has been done to find the changing regularity of the gas concentration in the room. It was later found that part of the CO2 gas tends to settle down remarkably as a kind of gas leakage. Later, the concentration of the planes in the room was made higher than the gas leakage source with the rate of concentration increment rising. In addition, the CO2 concentration near the wall was made higher up than in other parts of the room due to the resistance to the wall. The data of CO2 concentra- tion at different positions obtained experimentally were combined and made connected with an origin software to distribute the gas concen- tration in the whole space at a certain period of time. In the middle of the plane place, the CO2 concentration gradient in the process didn＇t seem as big as that at the beginning. But the gradient tends to be- come bigger and bigger with the time going on and a separate layer of CO2 was gradually resulted in. At this time, comparing the contribu- tions of CO2 concentration at different planes, it was found that the concentration on the horizontal plane closer to the ground was better evenly distributed as compared with the vertical planes. In the diffu- sion process, CO2 would be moving at its initial velocity in the radial direction and freely diffuse in its vertical directions. On the planes at different heights, the CO2 concentration and zones of higher concen- trations would drop with their heights. At this moment, CO2 tends to gather at the comer of the walls far from the leakage source and there was a zone with lower concentration under the leakage source. Thus it can be seen that the present research has provided a scientific basis in engineering for early detection of the gas diffusion and emergency res- cue of room-in dense gas leakage.