水力振荡器激励力形式对减阻效率的影响分析

Influences of Excitation Force Forms of the Hydraulic Oscillator on Drag Reduction Efficiency

现有研究对水力振荡器的激励力形式研究较少。考虑摩擦力的非线性效应,引入初始条件、边界条件和连续性条件,建立了带水力振荡器的钻柱动力学模型,利用有限差分法进行求解。以减阻效率作为目标函数,考虑钻柱失效和水力损失等约束,对减阻因素进行参数优化。研究结果表明:振幅和频率的增加均可有效降低摩擦力,提高减阻效率;在激励能量相同的条件下,大振幅和高频率下的激励力形式,即脉冲式激励力,更有利于提高减阻效率,3种因素的影响排序为激励力形式>振幅>频率。建议采用激励力形式2,即振幅45 kN,频率22.5 Hz。研究结果可为带水力振荡器钻柱的安全控制和优化设计提供一定的指导。

The excitation force forms of the hydraulic oscillator have been rarely reported.Considering the nonlinear effect of frictional forces,a dynamics model of the drill string equipped with the hydraulic oscillator was built by introducing the initial,boundary and continuity conditions and then solved via the finite difference method.Taking the drag reduction efficiency as the objective function and considering the constraints such as drill string failure and hydraulic loss,the parameters of drag reduction factors were optimized.The results show that the increases in amplitude and frequency can effectively reduce the frictional force and improve the drag reduction efficiency.Given the same excitation energy,the form of excitation force with large amplitude and high frequency,namely,the pulse excitation force,is more conducive to improving the drag reduction efficiency.The three factors are ranked as excitation force form>amplitude>frequency in an order of drag reduction efficiency.In the presented example,the No.2 excitation force form is recommended,which features an amplitude of 45 kN and a frequency of 22.5 Hz.The research results provide an important guidance for the safety control and optimal design of the drill string equipped with the hydraulic oscillator.