| This paper mainly aims at natural gas gathering and transmission system. The gas obtained from wells entrains sand particles. During the period of constant exploiting and production, the sand particles contained in the flowing medium are to induce sheet erosions, in which case pipe’s bends suffer most. However, the specific locations likely to get corroded, its influences on pipeline’s normal operation and corresponding preventative measures to be taken are still not clear. Therefore, aiming at aforementioned practical problems, this paper employs methods of fluid dynamics, erosion theory and coupled fluid-mechanics theorem for construction an erosion model; integrates basic theories with simulation data as well as ANSYS Fluent to conduct simulations of sheet erosions on pipelines’ bends. The key is to research how the inlet flow velocity, diameters of the sand particles and angles of the bends influence erosion effects. According to erosion cloud charts, the positions likely to be eroded are sieved out. Then with the utilization of Static Structural software, structural analysis on the bends is performed based on the coupling of fluid region and solid region. Finally, cloud charts of stress distribution and deformation displacement are obtained, whereby relevant preventative measures are generalized and proposed.Research contents in detail are as follows:(1) Single particle erosion theory, theory of deformation wear, erosion damage theory, the theory of micro cutting, theory of secondary erosion, forging and extrusion theory are determined. These theories provide references for determining damage patterns of pipeline wall caused by sand particles in gas pipelines. Aiming at fluid-mechanics theorem, data transfer between the interfaces, grid mapping and data exchange are analyzed;(2) An erosion model of the bends of gas pipelines is established, which offers a theoretical basis for subsequent simulations and computations. After the comparisons, the standard k-ε (k-epsilon) model is employed. In the first place the stress distribution of the bends’ structure is analyzed, and the conclusion that stress concentration appears at bends’ corner is obtained. Then the specific positions of pipelines to be studied are determined. Adopt finite volume method to conduct the process of discretization of the governing equation. Based on SIMPLE algorithm the coupling relationship of pressure and velocity is solved out. Finally, the coupling type in this paper is determined as one-way fluid-structure interaction.(3) A geometric model is established with Design Modeler module in ANSYS software package. Meshing program is used to conduct grid generation, and then the boundary conditions are determined. Finally specify the whole computational process of numerical simulation.(4) After specifying the parameters, simulation analysis of sheet erosion on stress-concentrated area is performed. Respectively from the perspective of velocity field, pressure field, discussions that how the inlet flow velocity, diameters of the sand particles and angles of the bends influence erosion effects are presented.(5) With the obtained erosion velocity cloud chart, it can be found that the bends of natural gas pipelines have potential dangers. Erosion mechanism of bends is determined after the generalization of numerical simulation results. Input flow field data into structure analysis software, perform computation on stress and displacement of the bends, conduct analysis on velocity sensitivity, obtain relevant cloud charts and check pipeline strength.(6) A number of preventative measures are proposed so as to effectively ensure the safety of pipelines. |
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