煤与瓦斯突出气固两相流的相间能质传递特征及非稳态输运机制

The pneumatic transport characteristic of outburst coal-gas two-phase flow has significant meaning for the continuous development of outburst disaster, which is also the main cause for the secondary disasters such as airflow reversal, gas explosion and coal dust explosion. But corresponding studies concerning this problem is few and short of the support from experiments. In this project, to gain the understanding of unsteady transport mechanism of coal-gas two-phase flow during the development stage of outburst, research methods such as flow pattern conversion boundary determination and tomographic analysis are applied to study the particle-size effect of inter-phase interaction of gas-solid in outburst two-phase flow; construct the governing equations of two-phase flow transport under the influence of multi-factors; obtain the equivalent kinetic model for the gas diffusion property of coal with different particle size; and reveal the control effect of rapid gas diffusion on outburst two-phase flow transport. On this basis, the bimodal particle size equivalent characterization method for heterogeneous outburst coal is explored; the unsteady transport mechanism of outburst two-phase flow with the assumption based on bimodal particle size distribution of coal powder/particle is established to calculate the flow field of outburst coal-gas flow, so that the spatiotemporal evolution characteristics of outburst two-phase flow during its motion process through the underground roadway can be obtained. The research results of this project will help to grasp the unsteady transport mechanism and characteristic parameters of outburst coal-gas flow in underground roadway as well as enrich the outburst mechanism, which will be of great scientific significance for the outburst disaster prevention and the establishment of underground emergency plan.

煤与瓦斯突出的气固两相流输运特征对于保证突出的持续发展具有重要意义，同时也是造成风流逆转、瓦斯及煤尘爆炸等次生灾害的主要原因，然而目前对该问题的研究相对较少且缺乏实验支撑。针对上述现状，本项目以突出发展过程中的两相流非稳态输运机制为研究对象，采用输运流型转换边界判定、层析成像分析等创新性研究方法，分析突出两相流相间能量-质量传递特征及其粒径效应，确立多因素影响下的两相流输运控制方程；获得不同粒径煤初始瓦斯放散特征的等效动力学模型，揭示瓦斯快速放散对两相流输运的控制机制。在此基础上，探索非均质突出煤的双粒度等效表征方法，构建基于煤粉/煤颗粒双粒度分布的突出两相流非稳态输运模型，并应用于突出两相流的流场解算，获得突出两相流在巷道内输运过程的时空演化特征。研究工作将有助于掌握突出两相流在巷道内的非稳态输运机制及特征参数，丰富突出机理，对突出灾害的预防和井下紧急避险方案的制定具有重要的科学意义。

煤与瓦斯突出是煤矿生产过程中遇到的一种极其复杂的瓦斯动力现象，为揭示突出发展过程中的两相流非稳态输运机制，本研究采用理论分析、实验室试验、数值模拟相结合的研究手段，获得了非均质突出煤粉化作用对孔隙结构的损伤特征，提出了描述不同粒径煤样初始瓦斯放散特性的等效动力学模型，分析了多因素影响下突出两相流的非稳态输运控制机制与冲击致灾特征，开展了初始瓦斯快速放散对突出两相流输运的影响研究，揭示了含瓦斯煤粉化、快速放散在推动突出发展中的作用。本文的主要研究工作及研究结论如下：.1）对粉化前后突出煤体的孔隙结构损伤特征开展精细定量表征，结果显示煤的比表面积/孔容均随粉化程度的增加而增长；<0.074mm煤粉的比表面积/孔容相比于1-3mm煤颗粒增加了数倍至数十倍不等。当煤被粉碎到<0.074mm后，部分煤样的比表面积/孔容数值发生突变，表明煤样孔隙已从局部损伤发展为全面破坏。.2）开展煤样0～60s初始瓦斯放散动力学特征实验，基于球形扩散模型和Fick第二扩散定律对煤样粒径和其初始瓦斯放散动力学特征之间的关系进行定量描述，描述不同粒径煤样初始瓦斯放散特性的等效动力学模型。经验证，该模型具有较好的可靠性与实用性。.3）开展多因素影响下的突出两相流输运控制机制与流型转换实验，对突出两相流的形成机制和运动特征开展研究，结果表明突出煤体和瓦斯气流间复杂的能量-质量传递作用导致两相流输运特征受到突出压力和煤样粒度构成的影响巨大。突出压力越大、煤粉比重越高，突出的强度就越大。当<0.25mm粉煤的质量比重超过2/3后，在较高的瓦斯压力下会形成两相流“自加速”现象，显著增强煤岩搬运能力与破坏力。.4）采用弱吸附性气体N2作为对照组开展突出两相流输运实验，对含瓦斯煤粉化、快速放散在推动突出发展中的作用进行研究。结果表明粉煤的初始瓦斯快速放散在推动突出发展的过程中起决定性作用，突出事故中总能量的73.3%～89.95%是由粉煤的初始瓦斯快速放散提供。