基于风洞模拟试验的冷却塔内烟气膨胀系数测量

Measurement of expanding coefficient of flue gas in cooling tower based on wind tunnel simulation test

利用环境风洞模拟冷却塔内烟气抬升,从而测量烟气膨胀系数。试验按照相似理论选取参数,模型和原型之间的烟气密度比、密度佛罗德数、试验风速比相等,由于塔内烟气升速比塔内空气升速大得多,如果气流升速不再随着塔内空气与烟气中心距离的增加而迅速减小,则认为测得烟气边缘,从速度分布可以得到烟气直径。试验结果发现:由于塔壁的作用,烟气膨胀系数β对环境风速不敏感,从烟道出口至塔顶处β平均值约为0.10,夹卷系数比膨胀系数小0.03左右。与水槽等试验结果相比,风洞试验模拟测出的膨胀系数比较接近准确值。

The environmental wind tennel was used to simulate flue gas raise and to measure the expanding coefficient of the flue gas. The test parameters were selected according to the similarity theory. The flue gas density ratio,the Densimetric Froude number and experimental air speed ratio of the model and the prototype are the same. In the tower,the flue gas raise speed is larger than the air raise speed. When the measured gas flow raise speed does not decrease rapidly along with increase of distance to the flue gas center,the the measurement point can be deemed as the flu gas edge. According to the speed distribution,the flue gas diameter can be obtained. It was found by the experiment result that due to the impact of the tower wall,the flue gas expanding coefficient β is not sensitive to environmental air speed.From the outlet of the gas duct to tower top,the average of β is about 0. 1,the entrainment coefficient is less than expanding coefficient by about 0. 03. Comparing with result of water channel experiment,the expanding coefficient measured by wind tunnel experiment is basically credible.