中文摘要：

以川渝地区油气田现场空气钻井用潜孔钻头为模拟对象,根据实体模型、底部包络面和实钻井眼建立流场模型,采用RNG k-ε方程作为气相湍流模型,用拉格朗日粒子追踪法描述固相,进行潜孔钻头的旋流场数值模拟。研究结果表明：气相在喷嘴出口形成的扇形面积小,未完全覆盖钻齿,钻齿处岩屑携带效率低;转盘转速对井底流场影响很小;钻头中心区域和切削结构中部（径向狭长区域）存在回流;流量分配不均和回流影响携岩效率和钻进速度;借鉴PDC钻头水力结构的设计思路,在潜孔钻头每个切削结构中心位置增加1个喷孔,在潜孔钻头中心增1个中心喷孔,发现改进后钻齿上分配的气量明显增加,过流流速增大,钻头中心区域回流现象基本消除,改进后结构有利于及时清除岩屑,减少重复切削,可以提高机械钻速以及延长钻头寿命。

英文摘要：

Taking Sichuan Chongqing district＇s oil field air drilling down-the-hole（DTH） bits as simulation object,flow model was established according to the entity model,bottom plane enveloping and borehole diameter.Taking RNG k-ε two equation turbulence model as gas model,and Lagrange particle tracing method for solid model,spiral flow field numerical simulation of DTH bit was completed.The results show that gas phase in the nozzle exit forms small fan area,which can not completely cover drilling teeth,so there is low efficiency of carrying cuttings in tooth;when drilling is empty,rotate speed has a little influence on bottom-hole flowing field.There exists backflow in bit center and cutting structure middle part（radial slim region）.Flow rate malapportioned and backflow affect cutting carrying efficiency and drilling speed.Reference to hydraulic structure design of PDC bit,a nozzle increases on each cutting structure center of DTH bit and a center nozzle on the center of bit.After the improvement,the gas distribution on teeth is significantly increased,and the backflow in bit center is basically eliminated.The improved structure can timely clear rock,reduce duplication of cutting,then it can improve drilling speed and extend life of bit.