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- 2015
叶片前缘旋流蒸汽冷却流动和传热的数值研究
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Abstract:
通过求解三维Reynolds？？Averaged Navier？？Stokes方程和标准k？拨赝牧髂Ｐ？,数值研究了旋流蒸汽冷却的基本原理,分析了冷气雷诺数和来流温比对流动和传热特性的影响,旨在阐明旋流蒸汽冷却的原理,总结其流动传热的变化规律。在此基础上对无量纲换热系数Nu、雷诺数Re和来流温比φ进行数值拟合,得到旋流蒸汽冷却的传热关联式。研究表明:冷气在旋流腔内的高速转动引起强烈的径向对流运动,使得换热增强;增大雷诺数能够增大冷气的涡量,有效提高旋流腔的换热系数,同时降低阻力系数;增大来流温比使得冷气的涡量增大密度减小,旋流腔的换热系数略有减小,阻力系数显著降低;综合换热因子随着雷诺数的增大而增大,随着来流温比的增大而减小;拟合的传热关联式与数值计算结果吻合良好,可以准确地预测蒸汽旋流冷却的换热系数。
The fundamental principle of steam vortex cooling is numerically investigated by means of 3？？D Reynolds？？averaged Navier？？Stokes equations coupled with the standard k？拨？ turbulent model. Effects of Reynolds number and inlet to wall temperature ratio on the flow and heat transfer characteristics are analyzed to clarify the mechanism of steam vortex cooling and to summarize properties of the flow and heat transfer. The heat transfer correlation of steam vortex cooling is obtained based on numerical data. The results show that violent convective motion is caused by the high speed rotational flow of steam in the vortex chamber, and results in an enhanced heat transfer performance. When the Reynolds number is increased, the heat transfer coefficient increases while the friction factor significantly decreases because of an increase in steam vorticity. An increase in inlet to wall temperature ratio results in a slight decrease in heat transfer coefficient, an increase in steam vorticity a decrease in density, and a clear decrease in friction factor of vortex chamber. The thermal performance factor increases as the Reynolds number is increased, and decreases as the temperature ratio is increased. The heat transfer correlation can be applied to predict the heat transfer coefficient of steam vortex cooling
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