報告書番号

L09004

タイトル（和文）

液滴衝撃エロージョン評価システムの高度化 -減肉量分布・最大減肉位置の近似評価手法の導入-

タイトル（英文）

Improvement of Evaluation System for Liquid Droplet Impingement Erosion - Introduction of Evaluation Methodof Thinning Rate Distribution and Maximum Thinning Rate Position -

概要 （図表や脚注は「報告書全文」に掲載しております）

発電プラントの運用・管理において重要な課題となっている配管減肉現象の内，
蒸気流中の液滴によるエロージョン(液滴衝撃エロージョン(LDI))について，
エルボ部の減肉面形状を高速に評価する手法を開発した．
これまで3次元計算が必要であった液滴の挙動計算を，
蒸気流速を簡素化することで1次元的に計算することで10秒程度の高速な計算を可能とし，
さらに蒸気流速分布を3次元計算を基にした相関式として与えることで，
精度の高い簡易評価手法とした．

概要 （英文）

Liquid droplet impingement erosion (LDI) is defined as an erosion phenomenon caused by high-speed droplet attack in a steam flow. Pipe wall thinning by LDI is sometimes observed in a steam piping system of a power plant. 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 had developed LDI evaluation system, core part of LDI Prediction Code, to organize past achievements and knowledge systematically. This system can evaluate the thinning rate with 1-dimensional flow evaluation within an acceptable time. However, this system cannot evaluate a shape of the thinning surface because the shape evaluation usually needs 3-dimensional calculation.
In this study, we tried to develop an evaluation method of the thinning surface shape by LDI within an acceptable time. We first assumed uniform flow distributions at elbow, and the droplet behavior was calculated 1-dimensionally. As a result, comparing with correlation equation developed by 3-dimensional calculations, the collision frequency was non-conservative. Then, we modified the flow distributions at elbow more actually. A correlation equation of the flow distributions was evaluated from 3-dimensional calculations. This is a function of the droplet position, and applied as the modified flow distributions. As a result, the collision frequency was modified and the evaluated surface shape agreed well with that by 3-dimensional calculation.

報告者

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