压差式管道机器人柔性多体系统流固耦合模型构建

流体驱动下压差式管道机器人的运动属于复杂的流固耦合动力学问题,通过数值模拟方法分析机器人的动力响应,评估机器人在管道内的巡线能力具有重要的工程意义。该文基于耦合的欧拉-拉格朗日(Coupled Eulerian-Lagrangian,CEL)方法,构建了机器人柔性多体系统的流固耦合动力学模型,以平均驱动压差、平均摩擦力和密封皮碗的米塞斯应力峰值为指标,评价机器人对管道环境的适应性。数值模拟结果表明,与3舱段管道机器人相比,5舱段管道机器人的平均速度和速度波动幅值分别降低5.3%和18.6%,但是平均驱动压差、摩擦力和峰值米塞斯应力分别增加了56.9%、95.7%和42.0%。由此,随着舱段数增加,密封皮碗的变形进一步增加,流体需提供更大的驱动压差克服摩擦力作用,但机器人系统的速度平稳性有所提高。3舱段和5舱段机器人在管道焊瘤高度20 mm、弯道角度90°、弯道曲率半径300 mm时的平均摩擦力、平均驱动压差以及密封皮碗的米塞斯应力峰值均达到最大值:3舱段机器人分别为0.98MPa、10.61kN和28.30 MPa,5舱段机器人分别为0.63 MPa、5.64 kN和24.16 MPa。因此,与3舱段机器人相比,在弯道与焊瘤约束的联合作用下,5舱段机器人需要消耗更多的流体压力能克服管道的约束阻力;更高的摩擦力将使密封皮碗磨损加速,削弱密封性能,而更高的米塞斯应力峰值也将增加密封皮碗的脆性断裂风险,导致5舱段机器人对于管道环境的适应性弱于3舱段机器人。研究结果可为管道机器人的巡线能力评价和设计优化提供参考。

Construction of fluid-solid coupling model of flexible multibody system for pipeline robots driven by differential pressure

The movement of the differential pressure pipeline robots in the pipeline driven by the fluid belongs to the complex fluid structure coupling dynamics problem. It is of great engineering significance to analyze the dynamic responses of the robots and evaluate the ability of the robot to patrol the pipeline by numerical simulation. Based on the coupled Eulerian Lagrangian (CEL) method, a fluid structure coupling dynamic model of the flexible multibody system for pipeline robots driven by differential pressure was constructed in this paper. The govening equations of the pipeline robots and its surrounding compressible Newton''s fluid were derived and represented with CEL frame. In order to efficiently describe the experienced large deformation process of the sealing cups, two-parameter Mooney-Rivilin model was used and its coefficients was obtained based on the uniaxial tensile tests of polyurethane. Based on the method of immersion boundary, the volume fraction in each fluid element contained wass used to track the fluid boundary by piecewise linear interface calculation. A novel penalty coupling method was used to simulate the interaction of the fluid with the robot by implementing a virtual spring bwteen the nodes at structural surface element and the anchor points at the fluid interface. The adaptability of the robot to the pipeline environment was evaluated by the average driving pressure difference, the average friction and the Mises stress peak value of the sealing cup. The parametric model of the pipeline robots with three and five cabins were developed to investigate the influence of pipeline geometrical parameters on the robots adaptability to internal pipeline environment. The numerical analysis results indicated that compared with the pipeline robot with three cabins, the average velocity and amplitude of velocity of the pipeline robot with five cabins were decreased by 5.3% and 18.6%,. and the running stability was better than that of the pipeline robot with three cabins, the average driving different pressure, friction force and peak values of mises stress of the sealing cups for the the pipeline robot with five cabins increased by 56.9%, 95.7% and 42.0% compared with the pipeline robot with three cabins, which showed that with the increase of the numbers of the cabins, the deformation of the sealing cup increased further, and the fluid needed to provide a larger driving pressure difference to overcome the friction, but the running stability of the robot was improved. For the pipeline robots with three and five cabins, the average friction force, the average driving pressure difference and the Mises stress peak value of sealing cups were all the maximum when the height of weld beading was 20 mm, the bending angle of bending section was 90° and the radius of curvature was 300 mm, thats of the pipeline robot with three cabins were 0.63 MPa, 5.64 kN and 24.16 MPa, respectivly, and 0.98 MPa, 10.61 kN and 28.30 MPa for the pipeline robot with five cabins Therefore, compared with the pipeline robot with three cabins, the pipeline robot with five cabins need to consume more fluid pressure energy to overcome the constraint resistance of the pipeline under dangerous conditions, the sealing cup is easier to wear, which weakens the sealing performance and has higher risk of brittle fracture. The research results can provide reference for the evaluation and design optimization of pipeline robot.