報告書番号

T03065

タイトル（和文）

蒸気加減弁に起こる流体振動現象の解明 -弾性支持実験による流体構造連成の影響の解明と流体-構造連成CFDコードの構築-

タイトル（英文）

Flow Oscillation on the Steam Control Valve- An experimental study of the Flow Inuced Vibration effect and development of FIV-MATIS code-

概要 （図表や脚注は「報告書全文」に掲載しております）

発電プラント等の蒸気系の流量調節弁は，弁の開度が中間状態の時に配管振動等により配管疲労を起こす可能性があり，プラントの高稼働率化の為にも振動原因の解明と改善策の提案が求められている．平成14年度，空気を用いた弁体の振動がない系において，弁が中間開度の時にのみ，準周期的な圧力脈動が発生する事が新たに判明した．そこで，本年度，弁体振動を考慮した流力振動実験を実施した．その結果，特定の領域において，準周期的な圧力脈動が，弁体の固有振動数に引き込まれて周期的な圧力脈動となり，さらに，弁体の減衰比が下がって弁体に自励的な振動が発生して大きな振幅となる事が判明した．また，構造の振動を取り入れたCFDコードを構築し，実験と同体系で計算を実施し，実験と良い一致を見た．今後は，格子やモデルの改良を行うと共に，湿り蒸気に対する実験やCFDコードの構築を行う必要がある．

概要 （英文）

A steam control valve causes vibration of the piping when the opening is in the middle condition. For the rationalization of maintenance and management in the plant, the valve should be improved, but it is difficult to understand the flow characteristics in detail by experiment because the flow around the valve is complex 3D structure and becomes supersonic (M>1). Therefore, it is necessary to clarify the cause of vibration and to develop improvements by the latest CFD (Computational Fluid Dynamics) technology.In current research, we found a valve-attached flow occurs and causes a quasi-periodic spike-type pressure fluctuation at only the middle opening condition in rigid support condition. As this fluctuation causes cyclic side load on the valve body, it is thought to be the cause of vibration.This report describes an effect of flow-induced vibration to the flow around the valve. We conducted some experiments with an elastic support and followings are found. In specific lift range, a resonance between valve and rock-in phenomenon, which the quasi-periodic pressure fluctuation is drawn in a natural frequency of the valve and becomes periodic, occurs. In addition, a damping ratio of the valve decreases and the amplitude has grown in the range.This report also describes a construction of CFD code with structure (grid) moving term. We add a grid moving term and a structure equation to our developed CFD code, 'MATIS'. This code agrees well with experiment and the validity of the code is confirmed.

報告者

キーワード