Experimental and numerical investigations on transient film cooling performances with trenched holes considering mainstream oscillation

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Heat and Mass Transfer Pub Date : 2023-10-09 DOI:10.1016/j.ijheatmasstransfer.2023.124799

Liwei Ma , Minmin Wang , Jinfu Chen , Hao Su , Jianhua Wang , Ran Yao

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引用次数: 0

Abstract

By a series of time-resolved experiments and large eddy simulations, the present work exhibits the transient behaviors and unsteady characteristics of film cooling with different trench configurations. The inevitable mainstream oscillation in turbine operation is considered, with a Strouhal number of 0.0128 and an amplitude of 0.50. The results show that: 1) The main instantaneous features are well captured by both experimental and numerical methods, and the transient behaviors of film cooling with trench design can be accurately predicted by the present large eddy simulation, even considering mainstream oscillation. 2) Without mainstream oscillation, film cooling unsteadiness is mainly caused by the temporal evolution of near-wall vortices, and the trench configurations exhibit a strong correlation on the unsteadiness level. The design with a higher trench height can evidently enhance the near-wall stability of film cooling while keeping a high time-averaged film effectiveness. 3) Film cooling unsteadiness is significantly aggravated by the mainstream oscillation. Under the present oscillation condition, the standard deviation of instantaneous film effectiveness is increased over 350.0 %, compared to the non-oscillation data. Meanwhile, the regions with high unsteadiness level are revealed with mainstream oscillation, which is mainly caused by the temporary coverage of cooling air in the target surface.

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考虑主流振荡的沟孔瞬态气膜冷却性能的实验与数值研究

通过一系列时间分辨实验和大涡模拟，研究了不同沟槽结构下气膜冷却的瞬态特性和非定常特性。考虑水轮机运行中不可避免的主流振荡，斯特劳哈尔数为0.0128，振幅为0.50。结果表明:1)实验方法和数值方法均能较好地捕捉到主要的瞬态特征，在考虑主流振荡的情况下，大涡模拟能较准确地预测沟槽设计下气膜冷却的瞬态行为。2)在无主流振荡的情况下，气膜冷却非定常主要由近壁面涡的时间演化引起，而海沟结构在非定常水平上表现出较强的相关性。较高的沟槽高度设计可以明显提高气膜冷却的近壁稳定性，同时保持较高的时间平均气膜效率。3)主流振荡显著加剧了气膜冷却不稳定性。在振荡条件下，瞬时膜效的标准差比非振荡条件下提高了350.0%以上。同时，非定常水平较高的区域出现主流振荡，这主要是由于冷却空气在目标表面的暂时覆盖造成的。

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来源期刊

International Journal of Heat and Mass Transfer 工程技术-工程：机械

CiteScore

10.30

自引率

13.50%

发文量

1319

审稿时长

41 days

期刊介绍： International Journal of Heat and Mass Transfer is the vehicle for the exchange of basic ideas in heat and mass transfer between research workers and engineers throughout the world. It focuses on both analytical and experimental research, with an emphasis on contributions which increase the basic understanding of transfer processes and their application to engineering problems. Topics include: -New methods of measuring and/or correlating transport-property data -Energy engineering -Environmental applications of heat and/or mass transfer