Acceleration of ice particle in the ice abrasive water jet and its rock breaking performance by numerical simulation
HUANG Fei,JIAO Yangyang,MI Jianyu,LI Shuqing,ZHAO Zhiqi,LIU Yong
为了高效增加煤层透气性强化煤层瓦斯抽采，首次提出采用冰粒磨料代替传统磨料的煤层 射流割缝增透新技术，以解决常规磨料射流煤层割缝中出现的堵塞孔隙裂隙等瓦斯渗流通道、增加 孔壁摩擦阻力导致卡钻抱死等缺陷。 然而，鉴于冰粒磨料与常规磨料的差异性，其加速特性与破碎 煤岩效果尚不清楚。 采用理论推演法研究了冰粒磨料的加速特性和速度分布规律，在此基础上构 建了数值计算模型分析了射流速度、冰粒体积分数以及围压对冰粒磨料射流破碎煤岩效果的影响 规律。 研究结果表明:1 冰粒磨料掺入高速流体后获得了先增大后减小加速趋势，最终其速度可 接近纯水的速度，大幅提升了冰粒磨料的冲击动能，为后续数值模型冰粒速度的赋值提供了依据; 2 数值计算结果出现 V 型破碎形态，同时冰粒磨料在冲击煤岩前后出现消融现象，符合现有文献 研究结果和工程实际情况，表明所建数值模型具有适用性;3 煤岩纵向破碎深度随冰粒磨料射流 速度的增加而线性增加，横向破碎宽度随速度先增加后趋于稳定，煤岩纵向损伤深度约为纵向破碎 深度的 1.13 倍;4 冰粒磨料掺入纯水射流后，煤岩的纵向破碎深度和横向破碎宽度均出现大幅增 加，随着冰粒磨料体积分数的增加，破碎深度和破碎宽度增加的趋势变缓，煤岩横向损伤直径约为 横向破碎宽度的 1.3 倍;5 煤岩所受围压大幅抑制了其在冰粒磨料射流冲击下的纵向破碎深度， 围压越大，纵向破碎深度越小，而横向破碎宽度却几乎不受围压的影响。 研究结果可为冰粒磨料射 流煤层割缝技术的工程应用提供一定的理论支撑，同时可进一步完善高压磨料射流破岩理论。
In order to effectively increase the permeability of coal seams, strengthen the gas drainage of coal seams，
a new technology of jet slotting coal seam using ice abrasive to replace conventional abrasive is firstly proposed in this paper. This technology may resolve the problems of blocking gas seepage channels such as pores and fissures,and sticking drill due to the increased friction resistance of hole wall,which are encountered in the application of conventional abrasive jet slotting coal seam. However,the acceleration and rock breaking performance of ice abrasive water jet remains unclear due to the discrepancy between ice abrasive and conventional abrasive. Theoretical deduction method was applied to study the acceleration and velocity distribution of ice particles. Then,a numerical model was established to monitor ice abrasive water jet breaking coal rock. It indicated that ① the acceleration of ice particle takes on a first increasing and then decreasing tendency since mixing with highspeed fluid. The final velocity of ice particles can nearly reach the pure water velocity,which can extremely increases the impacting kinetic energy of ice abrasive. This result can provide the velocity value for The numerical model.② The numerical simulation results show that a V shaped coal broken pattern appears and the ice particle melts after impacting on the coal rock. These results meet well with the findings of the previous literatures and the engineering projects,which reflects that the numerical model in this paper is suitable.③ The longitudinal crushing depth of coal rock increases linearly with the jet velocity,while the transverse crushing width takes on a first increase and then flat tendency with the jet velocity. The longitudinal damage depth is approximately 1.13 times of the longitudinal crushing depth.④ The longitudinal crushing depth as well as the transverse crushing width drastically increase ever since the mixing of ice abrasive and the increasing tendency slows down with the increase of ice abrasive concentration. The transverse damage width can reach 1.3 times of the transverse crushing width.⑤ The confining pressure extremely inhibits the longitudinal crushing depth of coal rock under the impact of ice abrasive water jet,whereas the transverse crushing width doesn′t change with the confining pressure. The study results of this paper can provide some theoretical supports for the application of ice abrasive water jet slotting coal seam. In addition,the findings in this paper can improve the theory of abrasive water jet breaking rock.
ice abrasive;coal seam slotting;acceleration mechanism;jet breaking rock;damage