Papers by Keyword: Droplet Impingement Erosion

Abstract: The process of nucleation of fatigue defects in metal alloys with different structural morphology is considered. A physical model was built, calculation expressions were presented, a numerical experiment was performed to determine the moment of nucleation of the critical-size defect in Fe-based alloys during high-speed droplet impacts. The physical model is based on the theory of dislocations. It is shown that the determining factor in the process of wear nucleation under dynamic cyclic loading has a structural factor. Depending on the structure and properties of the material, as well as on the nature of the loads, the critical fatigue defect develops in the form of cracks, pores or microcraters. Comparative data of calculations and bench tests for droplet impingement erosion were presented. The contribution of the nucleation stage during the incubation period of erosive wear of the materials studied was evaluated. Due to the fact that rigorous instrumental methods for determining the duration of the nucleation stage are absent, the usage of the proposed analytical model is recommended for this purpose.

Abstract: Flow-induced corrosion is one of the most prevalent tube damage mechanisms in steam generators of power plants. In this study, tube failure of a steam generator in Fars Combined Cycle Power Plant is evaluated. In addition to analysis of the measured tube thicknesses and the failure statistics data, computational fluid dynamic (CFD) methods are used to simulate flow distribution inside and outside of the tubes in one header of the low pressure circuit of the plant steam generator. The results show that regarding the created two-phase flow pattern inside the tubes, the droplet impingement erosion is the main source of tube failures in the bending areas where the extrados surface of the tubes are partially prone to the droplets. The results are useful for modifying the design of the steam generator from different viewpoints such as, optimal design for appropriate configuration of downcomer, header and footer and tube bending. Also, selecting suitable material for the steam generator tubes and implementation of protective coating in risky areas would benefit from the present results.