螺杆钻具瓣齿式万向轴密封结构流固耦合分析

Fluid-Solid Coupling Analysis on the Seal Structure of Flap Toothed Universal Shaft of PDM

在钻井过程中,螺杆钻具马达转子产生的轴向拉力以及密封套内腔中液压力的综合作用,使得密封套经常发生破损或鼓胀变形,进而导致运动副出现不同程度的磨损,缩短了万向轴的使用寿命。为了探究橡胶密封套出现破损和鼓胀变形的失效机理,在介绍密封瓣齿式万向轴的总体结构和原理的基础上,针对密封结构开展了流固耦合分析,研究了内部流场的流动规律、最大应力和最大位移分布规律,并通过现场试验进行了验证。研究结果表明:在瓣齿高速旋转剪切作用下,密封结构内部流体会产生明显的涡旋流动,流体速度和动压以旋转轴为中心呈对称分布且距离中心距离越大动压和旋转速度越大;瓣齿式万向轴的橡胶密封套主要承受内部流体的动压和轴向拉力作用,随着动压和轴向拉力增大,其最大应力和变形量都逐渐增大,且轴向拉力对变形量的影响大于动压所产生的影响。所得结果可为瓣齿式万向轴的密封结构优化设计提供重要参考。

In the course of drilling,the combined action of the axial tension generated by the rotor of positive displacement motor(PDM)and the hydraulic pressure in the gland cavity often causes the gland to be damaged or bulged,which then leads to different degrees of wear of the motion pair and shortens the service life of the universal shaft.In order to explore the failure mechanism of breakage and bulging deformation of rubber gland,on the basis of introducing the overall structure and principle of the sealed flap toothed universal shaft,fluid-solid coupling analysis was carried out on the seal structure,and the flow law,maximum stress,maximum displacement distribution law of the internal flow field were studied,which was further verified by field tests.The results show that under the action of high-speed rotating shear of the flap tooth,the fluid inside the seal structure forms obvious vortex flow,the fluid velocity and dynamic pressure are symmetrically distributed by taking the rotation axis as the center,and the greater the distance from the center,the greater the dynamic pressure and rotation speed are;the rubber gland of the flap toothed universal shaft mainly bears the dynamic pressure and axial tension of the internal fluid,as the dynamic pressure and axial tension increase,the maximum stress and deformation gradually increase,and the influence of axial tension on deformation is greater than that of dynamic pressure.The study results provide an important reference for the optimization design of seal structure of the flap toothed universal shaft.