A Probability Model Of Predicting The Sand Erosion Profile In Elbows For Gas Flow Based On Mechanical Analyses

With Hydrocarbon production reaching deep and ultra-deep waters more often,flow assurance plays an increasingly important role.The damage of pipelines caused by sand erosion is an inevitable problem encountered in the oil and gas transportation system.The elbow is one of most vulnerable fittings of pipelines.For gas-pipe bend,the drag force imposed on solid particles is relatively small due to the low viscosity of gas.It has been proved that incident particles in gas-pipe bend will initially impact on pipe walls in the trajectory of nearly straight lines instead of streamlines,causing the first erosion,then rebound randomly and subsequently impact the wall once again with a certain probability,resulting in second collision erosion.In the present work,a probability method is developed to analyze the impact-rebound-impact behavior of sand particle in elbows for gas flow.First,the Lagrange method is adopted to track motion trajectories of particles,and the motion rules of particles are deduced,according to which the magnitude and direction of first and second collision velocities can be calculated.Second,by analyzing the probability behavior of a single particle,holistic impact behavior of a large quantity of particles can be characterized.Last,rational erosive correlations are utilized to calculate first and second collision-induced erosion rates at specific positions in order to determine the location of the maximum erosion rate.The erosion profile along the centerline and the three-dimensional erosion profile can then be exhibited over the entire elbow surface.A large number of experimental data are compared with to examine the probability model based on the knowledge of second collision.The erosion profiles along the centerline and across the entire surface of the elbow,which can hardly be measured in experiments,are also calculated and analyzed through the probability model.The present work not only demonstrates the accuracy of the probability model,but also confirms that second collision of solid particles is an important behavior and plays a significant role in forming the erosion profile in elbows for gas flow.