实体PDC钻头流场数值模拟与实验验证

Numerical simulation and experimental checking for downhole flow field of a real PDC bit

利用计算流体动力学技术对聚晶金刚石(PDC)钻头(型号为BK432)的三维湍流进行了数值模拟。模拟中考虑了钻头的切削齿和射流喷嘴对流场的影响。流场的网格划分采用局部加密的混合网格形式,保证了计算精度和运算速度。流场的三维模拟结果揭示了钻头流场存在低速区、回流区和滞流区域,为钻头水力结构优化分析奠定了理论基础。为了对数值模拟的结果进行检验,建立了PDC钻头流体测试实验台架,利用粒子成像测速技术对PDC钻头4个喷嘴的出口流场进行了测试。将测试的喷嘴轴向速度与数值模拟结果进行了对比分析,两者吻合较好。

Three-dimensional turbulent flow of a polycrystalline diamond compact(PDC) bit was simulated by the method of computational fluid dynamics (CFD). The influences of teeth and jet nozzles on the flow field were considered in the simulated model. In order to meet the request of computation precision and speed, the mix grids with part closed were used in gird division of flow field. The three-dimensional simulated results show the slow flow, retarded flow and back flow areas of the bit. This sets theory foundation for futher research of the PDC hydraulic structure. In order to check the calculated result, an experiment was made. The flow-out fields of four bit nozzles were measured with particle image velocimetry(PIV) technology. The measured axial velocities of the bit nozzles are in good agreement with the results of numerical simulation.