冰粒磨料射流动力学特性及煤岩破碎机理研究

Water jet slotting technology is one of the effective solutions to permeability enhancements and gas drainage in coal mine. According to the indoor experiments, the ice abrasive water jet can enlarge the slotting range compared to the pure water jet; meanwhile the ice melting can avoid the problems induced by the traditional abrasive water jet, such as quality reduction of coal, slot jam and sticking of tool. However, some scientific problems encountered in the practice of ice abrasive water jet slotting coal seam, such as the jet dynamics, the damage mechanism of coal-rock and the influence of multi-fields and multi-factors, are still unknown. In this project, the acceleration model of ice particle considering the exchange of heat and mass will be established based on the study of the force of ice particle as well as the phase transition. The flow field, velocity field and the jet morphology will be captured. The distribution of ice particles in the jet will be analyzed statistically. Based on the above researches, the jet dynamics of ice abrasive water jet will be revealed. Then, the mathematical model of ice particles penetrating coal-rock will be proposed considering the breaking criterion and phase change of ice particles during the impacting process. So, the damage mechanism of coal-rock penetrated by the continuous ice particles can be gained. Thirdly, the experiments of slotting coal-rock by ice abrasive water jet will be conducted. The dynamic expansion of the slot and the multi-scaled damage morphology in coal rock will be monitored during the experiment. So, the comprehensive influence of thermal force coupling environment, the transport distance as well as the ice particle parameters on the damage of coal-rock can be clarified. At last, the physical model of ice abrasive water jet breaking coal-rock under the condition of the coupling of multi-field and multi-factors will be gained. The anticipated achievements can provide theoretical support for the application of ice abrasive water jet slotting coal-rock in coal mine.

水射流割缝技术是煤层增透抽采瓦斯的有效途径之一，室内试验表明冰粒磨料射流较纯水射流可大幅扩大割缝范围，且冰粒消融避免了传统磨料射流割缝所导致的煤质降低与堵塞卡钻等缺陷。然而冰粒磨料射流煤层割缝工程实践所涉及到的射流动力学特性、煤岩破碎机理与多场多因素耦合环境的影响机制等尚不清楚，本项目拟开展相变作用下的冰粒受力分析，建立考虑热质交换效应的冰粒加速模型，获取流场结构、速度场分布与射流形态，统计分析冰粒分布规律，揭示冰粒磨料射流动力特性；考虑冰粒撞击煤岩过程中的破碎准则与相变传热效应，建立冰粒侵彻煤岩的数学模型，揭示连续冰粒磨料破碎煤岩机理；开展冰粒磨料射流煤岩割缝试验研究，监测煤岩缝槽动态扩展规律与多尺度损伤形态，阐明地层热-力耦合环境、输送距离与冰粒参数等因素对煤岩破碎的综合影响机制，建立多场多因素耦合作用下的冰粒磨料射流破碎煤岩模型。预期成果可为冰粒磨料射流煤层割缝工程应用提供理论支撑。

射流割缝技术是煤层增透抽采瓦斯的有效途径之一，纯水射流割缝范围有限，磨料射流可大幅扩大割缝范围却易导致煤质降低与堵塞卡钻等问题。冰粒磨料射流能有效扩大割缝范围，且冰粒融化可避免传统磨料的缺陷。然而冰粒磨料射流动力学特性、煤岩破碎机理与多因素变量的影响机制等尚不清楚，因此本项目主要开展了“高压射流瞬态冲击动力特性”、“高压射流的喷嘴内外流场结构及其流动规律”、“磨料加速机理及磨料射流破岩机理”与“冰粒磨料射流冲击破碎煤岩机理及其影响因素”等四方面的研究。研究结果表明：①圆形喷嘴水射流的集束性最好，其冲击平面靶板瞬间产生的隆起区域最广，由此诱导产生的中心冲击压力最大，同形状喷嘴射流的峰值冲击压力均随着系统泵压的增加而呈现非线性的递增趋势，峰值压力持续时间随着泵压的改变而几乎保持不变；②不同外形轮廓射流自喷嘴喷出后，其轴向速度呈现随距离先缓慢减小后急剧减小的趋势，在相同距离处射流速度呈中心大外侧小的分布形式，其中圆形射流的中心速度最大；③冰粒磨料加入混合腔后，高速水流与磨料在极大的速度差作用下发生剧烈的碰撞促使磨料加速，当磨料运动到喷嘴收敛段时，收敛段积聚的能量被部分释放，使得磨料在收敛段被继续加速，由于磨料粒子的质量较大，提速较为缓慢，在进入直线段后仍与水有较大的速度差，使得磨料粒子继续加速并逐渐趋近于水，最终在喷嘴出口磨料的速度加速至纯水速度的 80%左右；④在同等工况下，冰粒磨料射流对煤岩体造成的损伤程度（包括破碎深度、破碎体积、内部损伤量等）介于纯水射流和陶粒磨料射流之间；冲击破碎煤岩完成后，冰粒磨料射流几乎全部融化并随着返水流走，而大量陶粒磨料滞留在破碎煤岩体内部；同等工况下冰粒磨料射流破碎单位煤岩体所消耗的能量比纯水射流和陶粒磨料射流均小，表明冰粒磨料射流具有较低的破岩能耗。研究成果为冰粒磨料射流煤层割缝的工程应用提供了一定的理论基础，同时完善了高压射流冲击破岩理论。