气流通过泡沫陶瓷的流阻实验与模型研究

An experimental study and modeling on the flow resistance of airflow through foam ceramic

研究气流在多孔介质内部的流动特性有助于指导天然气多孔介质燃烧器的设计。为此,对气流在泡沫陶瓷的流动特性进行了冷态实验,研究了气流速度、孔密度对流动阻力的影响,得出在相同空隙率条件下,孔密度与气流速度越大,流动阻力越大的认识;分析了气流分别在颗粒填充床和泡沫陶瓷中流动阻力的产生机理,建立了泡沫陶瓷结构模型,求出了比表面积及空隙率相等(即流动阻力相等)时泡沫陶瓷的孔密度与颗粒填充床颗粒直径间的函数关系,可直接利用制造商提供的泡沫陶瓷的特征参数(孔密度和空隙率),由颗粒填充床经典模型——Ergun方程来预测气流在泡沫陶瓷中的流动阻力,并确定了渗透阻力系数与惯性阻力系数的计算式,借此研究气流在泡沫陶瓷中的流动。实验结果表明,该方法对预测高空隙率的泡沫陶瓷流动阻力是有效的,为进行泡沫陶瓷多孔介质燃烧的数值模拟研究提供了参数计算依据。

The study on the flow characteristics of airflow through porous media is helpful in providing some guidance for the design and operation of porous media combustor.Therefore,a cold-state experiment is conducted on the flowing characteristics of airflow through foam ceramic.Through an analysis of the effect of flow rate and pore density (pores per inch,PPI) on the flow resistance,this experiment shows that under the same porosity,the bigger the PPI and flow rate,the greater flow resistance.Then,according to an investigation into the forming mechanism of flow resistance of airflow through particle-filled bed and foam ceramic respectively,a model is set up on the foam ceramic structure.By use of this model,a function relationship between the PPI of foam ceramic and the particle diameter of particle-filled bed is obtained under the condition of same specific surface area and same porosity (namely,the same flow resistance).Furthermore,by use of the characteristic parameters of foam ceramic including PPI and porosity,provided by manufactures,the Ergun Equation,a classic model of particle-filled bed,is adopted to predict the flow resistance of airflow through foam ceramic,and the calculation formulae of infiltration resistance coefficient and inertia resistance coefficient are thus determined.In this way,the flow properties of airflow through foam ceramic are thoroughly studied.The experimental study shows that this method is effective for the prediction of high-porosity porous foam ceramic,providing the basis of parameter calculation for the numerical simulation study of porous foam ceramic combustion.