转载溜槽内粉尘尘发机理及其逸散规律的研究

Transfer point has been recognized as the main dust source in bulk solids handling systems. The dust generation and dispersion can be effectively reduced by an optimized transfer chute design. However, the performance of transfer chutes on dust control is limited by the fact that it is difficult to resolve the dust generation mechanism in different scales and accurately predict the gas-solid flow characteristics. Because particle shape has a significant effect on the flow characteristics, the CFD-DEM coupled simulation method with non-spherical particle is used to investigate the complex dense gas-solid flow field and particles' force and motion in transfer chutes. Specifically, we use image processing technology to extract shape characterization of real particles; establish drag force model which is suitable for the dense complex non-spherical particles gas-solid system in high particle Reynolds number; study the method to deal with the real particle size distribution in DEM simulation; analyse the behaviors of non-spherical particles and the mechanism of action between gas and solid under different scales; Qualitatively and quantitatively predict different transfer chutes performance regarding dust control. The aim of this work is to disclose the mechanism of dust generation and dispersion in transfer chutes, which lays the foundation for transfer chutes scaling design and configuration optimization.

转载点是散料输送系统中最主要的粉尘污染源，使用设计合理的转载溜槽可以有效降低粉尘的产生和逸散。然而，由于无法解析不同尺度下的深层次机理、难以准确预测流动过程，使得转载溜槽很难达到预期的效果。鉴于颗粒形状对流动特性的重要影响，本项目采用基于非球形颗粒的CFD-DEM耦合数值模拟方法，对三维转载溜槽内复杂稠密气固耦合流场特征及颗粒受力和运动情况进行基础科学研究。具体内容包括：基于图像处理技术提取表征真实颗粒形状的参数；建立适用于高雷诺数下稠密复杂非球形颗粒气固系统的曳力模型；研究实际颗粒组成在DEM模拟中的处理方法；分析转载溜槽内不同尺寸颗粒间相互作用机制以及不同尺度下气固相间作用机理；对不同转载溜槽的粉尘情况进行定性及定量的预测。本项目旨在揭示转载溜槽内粉尘的产生机理及其逸散规律，为转载溜槽在结构放大、设计和优化等方面奠定理论和技术基础。

转载点是散料输送系统中最主要的粉尘污染源，使用设计合理的转载溜槽可以有效降低粉尘的产生和逸散。然而，由于无法解析不同尺度下的深层次机理、难以准确预测流动过程，使得转载溜槽很难达到预期的效果。本项目基于图像处理技术提取了表征真实颗粒形状的参数，基于实验数据获得高雷诺数下非球形颗粒的曳力模型；采用CFD-DEM耦合数值模拟方法，对三维转载溜槽内复杂稠密气固耦合流场特征及颗粒受力和运动情况进行研究；对数值模拟方法中的关键模型进行了适用性研究；探讨了影响数值模拟精度的影响因素，对转载溜槽的结构进行了优化设计。研究结果发现可以用多边形性P、长径比Ar、环形度Cr等参数来表征常见的不规则非球形矿物颗粒的形状；提出了新的不规则非球形颗粒曳力系数的关联式，但其精度并未比前人的结果有所提高，且适用范围较窄；CFD-DEM耦合方法较Two-Fluid方法精度提高了2.5%，但计算成本却增加了十几倍，所以就性价比而言，Two-Fluid方法更适合于大型工业设备的优化设计，CFD-DEM耦合方法只适合学术研究。研究表明CFD-DEM耦合方法可以用于对转载溜槽进行优化设计，但尚未形成系统的指导理论。