報告書番号

M11010

タイトル（和文）

LESによるガスタービンの膜冷却流れ構造と冷却特性の解明

タイトル（英文）

Large-eddy simulation of film cooling flow structure and cooling performance of gas turbine

概要 （図表や脚注は「報告書全文」に掲載しております）

ガスタービン翼の膜冷却流れを模擬した平板上の膜冷却流れを対象にLESを行い，吹出し比BRによる渦構造の違い，特に膜冷却効率に大きな影響を及ぼす双子渦の形成機構について詳細に調べた．その結果，吹出し比により冷却ジェットの渦構造は大きく変化することがわかった．BR=0.1の場合，後方渦とヘアピン渦が観察されるのに対して，BRが増加するとこうした渦構造に加えて，BR=0.5では馬蹄渦と随伴渦，ぶら下がり渦が形成されるようになり，BR=1.0ではさらにせん断渦やストリークが形成されることがわかった．吹出し比によって双子渦の実体は大きく異なる．双子渦の実体が異なるため，吹出し比によって膜冷却効率の特性は大きく変化することがわかった．

概要 （英文）

For understanding of film cooling flow fields of gas turbine blade, this report shows results of a series of large-eddy simulations of an inclined round jet issuing into a crossflow. Simulations were performed at four blowing ratio conditions, BR=0.1, 0.5, 0.7 and 1.0 and Reynolds number, Re=15,300, based on crossflow velocity and film cooling hole diameter. Results showed that cooling jet structure drastically changed with blowing ratio. A pair of rear vortex and hairpin vortex were observed for BR=0.1. A periodic ejection of horseshoe vortex, a pair of hanging vortex, a pair of rear vortex and hairpin vortex were observed for BR=0.5. Similar vortical structures to BR=0.5 were observed for BR=0.7 although horseshoe vortex remained at a leading edge of the hole exit. For BR=1.0, in addition o the former mentioned vortices, spanwise rollers and vertical streaks were observed on an upstream edge of the jet. The ubiquitous counter-rotating vortex pair was shown to originate mainly from the hanging vortices when BR was comparatively high. These vortices formed in the skewed mixing layer that developed between the jet and the crossflow fluid on the lateral edges of the jet. On the contrary the counter rotating vortex pair was shown to originate mainly from the hairpin vortex when BR was comparatively low. Since the origin of the counter rotating vortex pair differs as to blowing ratio, film effectiveness showed different trend as to blowing ratio.

報告者

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