報告書番号

M04006

タイトル（和文）

1300℃級ガスタービン初段動翼内部冷却の熱流動解析 -第3報 タービン翼前縁冷却流路を模擬したリブ付き三角流路の実験的検討-

タイトル（英文）

Numerical analysis of heat transfer in cooling passage for the 1st stage rotor blade of 1300℃ class gas turbine 3rd report, Measurement of flow and heat transfer in triangular channels with ribs

概要 （図表や脚注は「報告書全文」に掲載しております）

1300℃級ガスタービン初段動翼温度の解析精度向上を念頭に、熱的条件が厳しい翼前縁部の冷却流路を模擬した、これまで検討例がほとんどないリブ付き三角流路の伝熱流動実験を行った。実機で想定される流路断面形状の変化を考慮し、リブ高さが異なる４種類の直交リブ付き三角流路について調べた。その結果、リブ付き流路の平均摩擦係数は、流路断面形状に依らずリブによる流路閉塞率と良い相関を示す一方、平均熱伝達率は、翼内部の他冷却流路に用いられる傾斜リブ付き矩形流路に比較して小さい傾向にあること、流路閉塞率が同様でもリブ高さを局所的に変化させることにより熱伝達率分布が変化することを明らかにした。さらに、実験結果を基に冷却特性関係式を導出した結果、これまで翼温度解析の前縁部冷却流路に適用してきた円管近似に比較して、三角流路では熱伝達率が小さい傾向にあることが示され、温度解析の高精度化に向けた知見が得られた。

概要 （英文）

In order to contribute to accurate numerical analysis of temperature distribution of a 1300 Celsius degree class gas turbine rotor blade, characteristics of fully developed convective heat transfer in ribbed triangular channels were investigated by experimental measurements. The present target channels are modeling actual internal cooling structure of the blade leading edge which is exposed to severe thermal load. Four triangular channels which have different average heights of 90-deg. periodic ribs under the same cross section were measured in consideration of configuration of the actual cooling passage. Among those, three channels have uniform rib heights and the other one has a profile of the rib height which presents the same channel blockage ratio as one of the above channels. Heat transfer coefficients on the ribbed walls and velocity fields in the channels were measured under uniform heat flux condition on the ribbed wall.Experimental results indicate the following characteristics of the ribbed triangular channels.・Averaged friction factor of the ribbed channel is well correlated to the channel blockage ratio with the ribs.・Average heat transfer coefficient of the present triangular channel also increase with the blockage ratio, but is lower than that of angle-ribbed rectangular channel which is utilized as internal cooling structure in a mid-chord portion of the blade.・Distribution of the heat transfer coefficient varies depending on a local profile of the rib height under the same blockage ratio.Furthermore, cooling performances of the present triangular channels is modeled by using correlations of roughness functions of momentum and heat transfer obtained from the present measurements. As a result, it is shown that approximation of the ribbed circular tube that so far has been applied to the numerical analysis of the blade temperature yields higher heat transfer compared with actual triangular passage. That modeling for the ribbed triangular channels must improve accuracy of numerical prediction on the leading edge temperature.

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