喷射角对涡轮叶栅端壁气膜冷却的气动影响

Influence of injection angle on the aerodynamic aspects of endwall film-cooling in a turbine cascade

关键词:  涡轮叶栅  端壁+  二次流  气体喷射  薄膜冷却  喷射角+

Key words:  Turbine cascade  Endwall~+  Secondary flow  Gas injection  Film cooling  Injection angle~+

摘要:

在大尺寸低速平面叶栅风洞中,对前缘上游有单排气膜孔的涡轮导向叶栅端壁气膜冷却进行了气动实验。在喷射角25°,35°和45°以及吹风比1,2,3下详细测量了叶栅通道中的三维流场,得到了全速度和二次流速度分布,并由此计算了二次流动能的大小。着重研究了喷射角对端壁气膜冷却的气动特性和对叶栅通道中特别是端壁附近的流场结构的影响。数据表明减小喷射角度可以减小通道涡的强度和尺寸,使冷气射流核心更贴近壁面,但同时也明显地增大了壁面附近的气流速度。在高吹风比下,35°喷射时射流将冷气输运到压力边的能力比25°喷射和45°喷射都要强。

Abstract:

Detailed aerodynamic measurements were carried out in the passage of a large-scale low speed turbine cascade with single row injection on the endwall upstream of leading edge. Full velocity contours and secondary flow velocity vectors were obtained with coolant injection at blowing ratio 1, 2, 3 and injection angle 25°, 35°, 45°, respectively. The corresponding kinetic energies of secondary flow were also determined. The influences of injection angle on the aerodynamic aspects of endwall film cooling and on the secondary flow vortex structures in the near endwall region of the passage were studied. The results reveal that the strength and the size of passage vortex could be reduced by decreasing injection angle. It was observed that the cores of coolant jets could stay closer to endwall by decreasing injection angle, but the flow velocity in the neighborhood of endwall increases remarkably as well. At high blowing ratio, the capability of transporting coolant to the pressure side at injection angle 35° is greater than that at injection angle 25° and 45°.