報告書番号

T03064

タイトル（和文）

蒸気加減弁に起こる流体振動現象の解明 -中間開度時における弁体・弁座形状の影響及び大開度時における衝撃波振動の発生-

タイトル（英文）

Flow Oscillation on the Steam Control Valve-Effects of valve/valve seat shape in the middle opening,and a possibility of a shock oscillation in the large opening-

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などが発生して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を考慮しない系での基礎試験において，弁が中間開度の時にのみ，流れが弁体に付着する事が原因で広いスペクトルを持つ準周期的なスパイク状の圧力脈動が発生する事が新たに判明した．そこで，本年度はこれを抑制する形状の提案を行った．まず，弁座形状を変化させて実験を行ったが，完全には圧力脈動を抑制できなかったため，新たな弁形状を提案し実験を実施した結果，弁体を長く延ばした延長弁を用いると圧力脈動が抑制された．また，出力が大きい条件において弁体付近に衝撃波振動が起こる可能性が判明したため，今後は新形状弁による衝撃波振動の抑制効果を調べる必要がある．

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 valve/valve seat effect for the flow control. First, we conducted the experiment of the valve seat effect, but it’s impossible to control the flow fluctuation completely. Then, we suggest new shape valves (cut valve, extended valve) and checked their performance with 2 types of valve seat. As a result, the extended valve can control the fluctuation completely with all valve seat shape. And we also checked the flow condition in the large opening condition with our CFD code,’MATIS’, and found a possibility of the shock wave oscillation around valve. As this phenomenon also causes large pressure fluctuation, we need to check the controllability of the shock oscillation with new shape valve in the future.

報告者

キーワード