高压煤粉气固两相射流动力学及破煤特性研究

Study on Dynamics and Coal Breaking Characteristics of Gas-Solid Two-Phase Jet with High-Pressure Pulverized Coal

为进一步强化高压射流破煤岩能力,降低能耗,结合原位物理破碎流态化开采理论,提出了一种高压煤粉气固两相射流破煤方法。基于DPM离散相模型阐明了气固两相射流的流场结构特征及煤粉加速规律,构建了煤岩RHT本构模型,采用DEM-FEM方法建立了耦合模型,探究了冲蚀过程中煤岩内部应力波传播及动态损伤规律,并对比分析了矸石水射流和煤粉粒子射流的能耗及破煤效果。结果表明:随着射流压力的升高,流体状态从过膨胀转变为欠膨胀,流场马赫盘结构愈发明显;提高射流压力可以增大煤粉粒子射流的冲击能量,有利于强化煤岩内部应力波效应,延长应力波有效作用时间,加剧煤岩损伤,煤岩更易被剪切形式所破坏;随着传播距离的增大,应力波会出现一定程度的频散和幅值衰减,且衰减速率随射流压力的增大而增大;相同冲击速度下,煤粉粒子射流对煤岩的宏观损伤更为严重,其冲蚀率为矸石水射流的1.78倍,对应比能耗仅为矸石水射流的56%,表现出更优的破煤特性。研究结果可为气固两相射流破煤的应用提供一定的理论支撑。

In order to further strengthen the ability of high-pressure jet to break coal rock and reduce energy consumption,a coal breaking method of gas-solid two-phase jet with high-pressure pulverized coal was proposed based on the theory of in-situ physical crushing fluidized mining.Based on the DPM discrete phase model,the flow field structure characteristics of gas-solid two-phase jet and the acceleration law of pulverized coal were clarified.The RHT constitutive model of coal rock was constructed.The coupling model was established by DEM-FEM method,and the propagation of stress wave and dynamic damage law in coal rock during erosion were explored.The energy consumption and coal breaking effect of gangue-water jet and pulverized coal particle jet were compared and analyzed.The results show that with the increase of the refractive flow pressure,the fluid state changes from over-expansion to under-expansion,and the Mach disk structure of the flow field becomes more obvious.Increasing the jet pressure can increase the impact energy of the pulverized coal particle jet,which is beneficial to strengthen the internal stress wave effect of the coal rock,prolong the effective action time of the stress wave,aggravate the damage of the coal rock,and the coal rock is more easily destroyed by the shear form.With the increase of propagation distance,the stress wave will have a certain degree of dispersion and amplitude attenuation,and the attenuation rate increases with the increase of jet pressure.At the same impact velocity,the macroscopic damage of coal rock by pulverized coal particle jet is more serious,and its erosion rate is 1.78 times that of gangue-water jet,and the corresponding specific energy consumption is only 56%of that of gangue-water jet,showing better coal breaking characteristics.The research results can provide some theoretical support for the application of coal breaking by gas-solid two-phase jet.