B102 液滴衝撃エロージョン評価システムの実用性の向上(流れ加速型腐食・エロージョン・振動,OS6 保全・設備診断技術)

Abstract

Liquid droplet impingement erosion (LDI) is defined as an erosion phenomenon caused by high-speed droplet attack in a steam flow. In a power plant, pipe wall thinning by LDI is observed steam piping system. Because LDI usually occur very locally and is difficult to detect, a prediction of LDI location is required for the safety of the plant system. Therefore, as ultimate objectives, we set the development of the prediction tool of LDI location that can use in power plants easily (LDI Prediction Code). In previous researches, we developed LDI evaluation system, core part of LDI Prediction Code, to organize past achievements and knowledge systematically. However, this system needs 3-dimensional simulations to evaluate the mass flow rate and the droplet behavior which are important parts of the system. As 3-dimensional simulations have heavy loads, it is difficult to use as is in power plants. In this study, we tried to develop new methods to evaluate the mass flow rate and the droplet behavior easily instead of 3-dimensional simulations and to modify the 1-dimensional flow evaluation code "MATIS-SP" to apply high-wetness and water region. For the mass flow rate evaluation, we assumed the flow choked at the orifice, and suggested an analytical method with experimental and computational results. This approach agrees well with experiments and computations within acceptable range. For the flow evaluation, we developed a new code "MATIS-SP2" by adopting a simplified model that only considered pressure loss evaluation and applicable to all region of the steam/water. And for the droplet behavior evaluation, we conducted much simulations of the droplet behavior and suggested the correlation between droplet collision rate and flow state quantities from simulation results. Finally, we suggested new evaluation system with no 3-dimensional simulations and wide applicable region, and compared them with previous system by LDI evaluation in model system.