三維複合孔構型薄膜冷卻凸面熱流場結構之數值模擬與分析

Effect of Compound Angle on the Film Cooling over Three-dimension Convex Model Including the Coolant Plenum

苗志銘(Jr-Ming Miao) ； 覃宏科(Hong-Ka Ching)

《中國航空太空學會學刊》 37卷2期 (2005/06) Pp. 181-191

https://doi.org/10.6124/TAASRC.200506_37(2).09

摘要

本研究目的在於利用計算流體力學模式探討不同複合角構型下薄膜冷卻葉片凸面之熱流場特性，模擬對象爲具冷卻流供應槽簡化實體構型之固定曲率半徑測試件模型。研究重點爲呈現與明瞭冷卻流由矩形冷卻流供應槽注入後，由具不同流向角與跨向角複合組合（流向角爲35度，跨向角有0度、45度與流向角90度而跨向角爲35度）之單排五孔冷卻噴流口噴出而與主流場交互作用下所引發之三維複雜熱流場結構與測試件表面之絕熱薄膜冷卻效率分佈情形，另吹出比(BR)的設定，計有0.5、0.75、1.0、1.25與2.0。 爲完整地模擬出冷卻流由供應槽流入，再透過各冷卻流噴孔流出並與主流場交互作用之流動機制，本研究建構多區塊且結構性網格系統之冷卻流供應槽、單排噴孔通道與主流通道。數值運算器則是以有限體積法架構下之軟體CFX4.4，求解雷諾平均那維爾－史托克方程組，而紊流特性係採用雙方程式之低雷諾數k-ε紊流模式進行流場模擬。當吹出比爲0.5時，模擬結果與利用暫態熱液晶技術所量測之實驗值相互比對，在跨向平均薄膜冷卻效率分佈上相當吻合。分析模擬結果可得如下結論：以流向角35度且跨向角爲45度時在相同吹出比下有較高之表面絕熱薄膜冷卻效率值；複合角的效應對於噴射孔附近區域的冷卻效果明顯高於不具複合角的冷卻噴流情形。本研究同時也發現在不同複合角下，反漩渦流對之形成與薄膜冷卻效率之分佈間有顯著之影響。

關鍵字

計算流體力學 ； 薄膜冷卻 ； 冷卻流供應槽 ； 吹出比 ； 複合角

並列摘要

The purpose of this paper is to simulate the adiabatic film cooling effectiveness distribution over a convex surface with various compound angle of coolant pipe by computational fluid dynamics method. In order to approximate the practical blade configuration, a full 3-dimension model includes coolant plenum, film cooling holes with different spanwise angle and convex test section was constructed. The mainstream flow conditions are as follows: the Reynolds number (Re) is 2,200, and the density ratio (p(subscript c)/p(subscript m)) is 1.05. Various coolant-to-mainstream blowing ratios, 0.5, 0.75, 1.0, 1.25 and 2.0 are to study the effects on film cooling efficiency.
In addition to the blowing ratio effect, three various spanwise angles, 0°, 35° and 45°, are respectively investigated. In order to simulate the complicate flow phenomena, a multi-blocks computational grid system is constructed by an ICEM/CFD, three-dimensional finite-volume commercial solver, CFX 4.4, was used to solve the Navier-Stokes governing equations. The low-Reynolds number k-ε turbulence model is used for turbulence closure in this study. These computed results on spanwise averaged film-cooling effectiveness agree reasonably well with the experimental data at blowing ratio of 0.5. These results reveal that (1) the injection angle 35°and spanwise angle 45° offer the better adiabatic film cooling effectiveness at different blowing ratio; (2) the film cooling effectiveness with compound angle has higher efficiency than those without compound angle; (3) the distribution of counter-rotating vortex pairs has direct significant effects on the distribution of film cooling efficiency.

並列關鍵字

Computational fluid dynamics ； Film cooling ； Coolant plenum ； Blowing ratio ； Compound angle