STUDY ON THE IMPROVEMENT OF AIR CURTAIN PERFORMANCE BY THE MANIPULATION OF VORTICES

(1)搭建了一个加热箱作为空气幕性能测试的实验装置。箱体尺寸为1.5m×1.5m×1.5m，箱体开口门处安装风幕。空气从顶部排出并被吸入底部。电热带贴在地板上，用热电偶测量箱体内外的温度。数据记录在混合记录器中，并由数据处理计算机处理。实验结果表明，该箱体性能良好，可用于空气幕的研究。(2)测量了锯齿状粗糙度扰动下空气幕的换热特性，并与无扰动时的换热特性进行了比较。箱内外温差增加了50个百分点，这是由于锯齿形粗糙度产生的三维扰动抑制了气幕中的大尺度旋涡。(3)通过射流实验研究了三维扰动对射流扩散的影响。锯齿状粗糙度和软纤维附着在射流出口处，以产生三维扰动。结合实测的速度剖面讨论了扩散特性。结果表明，扰动对射流扩散有很好的抑制作用。根据实验结果，我们提出了锯状粗糙度和柔软纤维的合适特征。

(1) A heating box was built up as the experimental apparatus to measure the performance of air curtain. The size of the box is 1.5m×1.5m×1.5m, and an air curtain is installed at an opening door of the box. The air is issued from the top and sucked into the bottom. The ribbon heater is pasted on the floor, and the temperatures inside and outside of the box are measured by thermocouple. The data are recorded in a hybrid recorder and processed by a data processing computer. The performance of the box was confirmed to be good for the study of air curtain.(2) The heat transfer through the air curtain perturbed by saw-shape roughness was measured and compared with that without the perturbation. The difference of the temperatures inside and outside of the box increased fifty percents, which results from the suppression of the large-scale vortices in the air curtain by the three-dimensional perturbation generated by saw-shape roughness.(3) The effect of three-dimensional perturbation on jet diffusion was studied by the experiments of jets. The saw-shape roughness and soft fibers were attached at the jet exit to generate three-dimensional perturbations. The characteristics of diffusion were discussed by considering the measured velocity profiles. The result shows that the perturbations are very effective to suppress jet diffusion. From the result we suggest the suitable features of saw-shape roughness and soft fibers.