长距离煤炭气力输送中多尺度异形体颗粒系统动力学行为研究

The objectives of this project are to change the method of raw coal transportation underground, cut down the construction budget of roadway excavation, and reduce the cost consumption of raw coal transportation. In addition to the contact dynamics behavior between large-size irregular coal particle and pipe wall, taking the coupling action between particle and flow field into account, the system dynamics are also studied by using the several methods: tomography technology, gas-solid two-phase flow theory, system dynamics theory, fluid mechanics, damage mechanics, discrete element method and finite volume theory. The three-dimensional discrete element models which characterize the coal and gangue particles correctly are constructed. Based on this model, the relationship between pipe wear characteristics and particle breakage dynamics under pneumatic conveying flow field are researched. Additionally, the characteristics of the surface profile and the fracture distribution in the heterogeneous coal particles are obtained. Considering the contact dynamics behavior between the particles and the pipe-wall as the particles and flow field coupled, several models are built, such as the interaction collision dynamic model, sliding dynamic model and rolling dynamic model of particles and pipe-wall. Besides, the swirling flow pneumatic conveying model, axial flow pneumatic conveying model, particles and pipe-wall coupling dynamics model and pneumatic conveying system coupling model are also established. The experiments about the coal particles pneumatic conveying are carried out. The interaction coupling dynamics behavior between particles and pipe-wall are further studied when they are in different pipe structure and flow field structure. On the basis, the foundation is laid to develop the clean, safe and efficient of the long-distance coal pneumatic conveying systems Furthermore, the environmental protection and safe-efficient of the special-shaped particles pneumatic conveying system are improved.

本项目以改变井下煤炭输送格局、降低巷道建设和输送成本为目标，运用断层扫描技术、气固两相流理论、系统动力学理论、流体力学、损伤力学以及离散元与有限容积等理论和方法，开展多尺度不规则煤炭颗粒与管壁接触动力学行为以及颗粒与流场耦合作用下的系统动力学研究。在建立煤炭颗粒三维多尺度离散元模型、掌握异形体煤炭颗粒的表面轮廓特征及裂隙分布特性的基础上，考虑颗粒与流场耦合作用时颗粒与输送管道的接触动力学行为，建立流场耦合条件下多尺度异形体颗粒与管壁互作用碰撞、滑移和滚动动力学模型，研究气力输送流场中的管道磨损特性与颗粒破碎动力学关系；建立旋流和轴流气力输送模型、异形体颗粒与管壁耦合动力学模型并进行长距离煤炭气力输送系统实验研究，深入研究不同管道结构与流场结构下颗粒与管壁互作用耦合动力学行为，为清洁、安全、高效的长距离煤炭气力输送系统的研发奠定基础，提高异形体颗粒气力输送的清洁环保性和安全高效性。

气力输送技术是一种清洁、可循环利用的运输方式，是实现煤炭绿色运输的有效途径，具有占地空间小、环保清洁且自动化程度高等优点，但同时也存在着管道磨损、颗粒破碎以及收料复杂等问题。根据煤矸颗粒的细观结构及宏观物理机械性质的差异，提出利用数字图像技术对煤与矸石颗粒内部细观结构及其破损特性进行研究；结合气固两相耦合理论、计算流体力学与离散元耦合数值模拟方法（CFD-DEM）和颗粒输送实验，对煤炭颗粒在直管、弯管以及旋流场中的运动学和动力学行为、长距离管道气力输送基础理论以及旋流气力输送系统性能展开研究；设计了一种组合式旋转分离器，对其内部流场分布、压降、收集效率和分级效率展开研究。研究发现，煤岩破碎的碎片集中在壁面-颗粒碰撞区域附近，破碎率随着球形度系数的增加而减小；推导出煤炭颗粒在流场中的运动微分方程、颗粒碰撞运动方程及接触动力学方程，旋流场内轴向速度峰值区域形状随流场流动呈准周期性旋转，有益于扰动颗粒运动，旋流场内颗粒呈现明显的螺旋运动，并保持较长距离的悬浮运动状态；弯头对管壁磨损有显著影响，磨损主要集中于外侧管壁的中部区域。随着颗粒球形度增大，弯头管壁平均磨损率均呈现倾斜“S”状变化，旋流输送时弯头管壁磨损率较轴流场有显著降低；对水平管道颗粒拾取过程进行分析，发现存在最佳旋流数，煤炭颗粒拾取率最大；气流速度对提升弯管内的压降起着至关重要的作用，提升弯管肘部45°处压降比弯管进出口压降更大；当转子转速为160 r/min的偶数倍和奇数倍时，分离器收集效率分别达到峰值和谷值。以上研究结果为煤炭颗粒气力输送工业应用提供理论和试验依据，拓宽了气力输送技术应用领域。