A probability model of predicting the sand erosion in elbows for annular flow

Annular flow is a common flow pattern in oil and gas pipelines for its stability and efficiency. During the oil and gas production, sand particles are inevitably carried by annular flow to continuously impact on elbows, and thus make the sand erosion in elbows a notable problem. In the present work, both the first and second collisions are taken into account in the collision probability analysis. The decay effects of liquid film on particles are considered in calculating the impact velocities of particles, and the particle impact information is introduced into erosion correlations to estimate the erosion ratio. By combining the collision probability models and the erosion correlations, a novel probability model for annular flow is developed to predict the sand erosion in elbows. Numerous experiments are employed to examine the accuracy of the present model, and the applicability and efficiency of the probability model are demonstrated by comparing with other erosion models. Finally, the effects of first and second collisions on the formation of erosion profiles, as well as the relations between the erosion profile and the superficial gas velocity, superficial liquid velocity and curvature of elbow, are investigated in detail to acquire more knowledge of the sand erosion in elbows under annular flow conditions.