分形理论分析风口回旋区的边界

Analysis of the Raceway Boundary Using Fractal Theory

基于分形理论更能准确地界定风口回旋区边界。建立COREX熔化气化炉的半周三维冷态模型,利用高速摄影的方法跟踪冷态模型内示踪粒子的运动,得到冷模型观察面板处风口回旋区的颗粒运动信息。通过对大量颗粒运动信息的处理得到风口回旋区范围的颗粒速度标量场,最后运用分形理论对利用不同颗粒速度大小等值线界定的回旋区边界的"不规则"程度进行了研究。结果表明:在回旋区内部颗粒快速运动的空腔区,分维数基本不变,且接近于欧几里得维数1;在停滞区,分维数也基本不变,其数值大致为1.4;从空腔区到停滞区分维数逐渐增大;将停滞区分维数基本不变的速度值作为界定回旋区边界的标准,可以确定回旋区的形状和大小,并可通过余维相加定律计算出三维风口回旋区的内表面积;为风口回旋区的宏观动力学计算以及数值模拟提供准确的边界条件。

The raceway boundary can be precisely defined based on fractal theory. A three-dimensional semicircular cold model was established and the particle motion information was also obtained by using high-speed photography method to track the trace particle motion. The particle velocity scalar field was obtained through processing the large amount of particle motion information, and finally the irregular degree of raceway boundary defined by isolines under different particle velocity was discussed. The results show that the fractal dimension which is close to Euclidean dimension 1 remains unchanged in the cavity zone. The fractal dimension with the dimension of 1.4 also remains unchanged in the stagnant zone. The fractal dimension increases gradually from cavity zone to stagnant zone. The velocity obtained under the fractal dimension of stagnant zone can be used as the criterion to define the raceway boundary, then the shape and size of raceway can be precisely obtained and the internal surface area of raceway can be calculated by using the law of additive codimensions. And then it can provide precisely boundary conditions for macro dynamic calculation of raceway and numerical simulation.