尖脊结构对孕镶金刚石钻头表面流场的影响研究

Study on effect of ridge arrangement on surface flow field of an impregnated bit

摘要:

孕镶金刚石钻头的唇面结构是影响其碎岩效率与钻进性能的关键因素，尖脊孕镶金刚石钻头的尖脊排布方式直接关系到孔底钻井液对唇面的冷却与清洗效果。为探究尖脊排布方式对钻头表面流体流动特性的影响规律，设计顺向、逆向、对称三种尖脊排布方式，外径78 mm、内径48 mm的尖脊孕镶金刚石钻头唇面。以清水为介质，利用ANSYS Fluent对钻头表面流体流动进行动力学仿真。在钻头62.83 rad/s转速的条件下对比研究不同尖脊排布方式下钻头表面流体的流动特性与钻头表面流速分布，阐明结构参数对钻头表面流体流动特性的影响规律。仿真结果表明：三种排布方式表面流体均在水口附近呈现流速最高，可达7.92~9.15 m/s；脊间高流速区域集中于尖脊迎向转动方向前端，顺向排布对脊间流体流动速度的影响最小，尖脊前端流速可达5.60 m/s，较逆向、对称两种排布方式分别提升了约17.89%和2.04%，且高流速区域能够覆盖三条尖脊前端高温区域；顺向排布脊间流速可达3.20 m/s，较逆向、对称两种排布方式分别提升了约102.50%和247.80%；同时，顺向排布方式尖脊对流体的流迹影响最小。综合研究表明，尖脊顺向排布最有利于维持钻头表面流速，并改善尖脊的冷却条件及脊间、孔底岩屑的清理效果。

Abstract:

The crown structure of an impregnated diamond bit is a critical factor affecting its rock-breaking efficiency and drilling performance. The ridge arrangement of a ridged impregnated diamond bit directly determines the cooling and cleaning performance of drilling fluid acting on the bit crown at the bottom hole. To investigate how ridge arrangement affects the flow characteristics of fluid over the bit surface， three ridge layouts （forward， reverse and symmetric） are designed for bit crowns of ridged impregnated diamond bits with an outer diameter of 78 mm and an inner diameter of 48 mm. Using clean water as the working medium， ANSYS Fluent is adopted to conduct hydrodynamic simulations of fluid flow on the bit surface. Under a bit rotational speed of 62.83 rad/s， the flow characteristics and velocity distribution of surface fluid with different ridge layouts are compared， and the influence of structural parameters on fluid flow behavior is clarified. The simulation results show that the maximum fluid velocity for all three layouts occurs near the water ports， ranging from 7.92 to 9.15 m/s. High-velocity zones between ridges concentrate at the front edge of ridges facing the rotation direction. The forward layout imposes the weakest disturbance on inter-ridge fluid velocity. The flow velocity at ridge fronts reaches 5.60 m/s， approximately 17.89% and 2.04% higher than those of the reverse and symmetric layouts， respectively， and the high-velocity zone can cover the high-temperature regions at the front of the three ridges. The inter-ridge velocity of the forward layout reaches 3.20 m/s， which is about 102.50% and 247.80% higher than the reverse and symmetric layouts， respectively. Meanwhile， the ridges in the forward layout exert the least influence on fluid streamlines. Comprehensive analysis demonstrates that the forward ridge arrangement is optimal for preserving surface flow velocity， improving ridge cooling conditions and enhancing the removal of cuttings between ridges and at the bottom hole.