An experimental investigation has been performed to measure average and local mass transfer coefficients on the tip of a gas turbine blade using the naphthalene sublimation technique. The heat/mass transfer analogy can be applied to obtain heat transfer coefficients from the measured mass transfer data. Flow visualization on the tip surface is provided using an oil dot technique. Two different tip geometries are considered: a squealer tip and a winglet-squealer tip having a winglet on the pressure side and a squealer on the suction side of the blade. Measurements have been taken at tip clearance levels ranging from 0.6% to 3.6% of actual chord. The exit Reynolds number based on actual chord is approximately 7.2 x 10~5 for all measurements. Flow visualization shows impingement and recirculation regions on the blade tip surface, providing an interpretation of the mass transfer distributions and offering insight into the fluid dynamics within the gap. For both tip geometries the tip clearance level has a significant effect on the mass transfer distribution. The squealer tip has a higher average mass transfer that sensibly decreases with gap level, whereas a more limited variation with gap level is observed for the average mass transfer from the winglet-squealer tip.
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机译：已经进行了实验研究，以使用萘升华技术来测量燃气轮机叶片的尖端上的平均和局部传质系数。可以应用热/质量传递类比来从测量的质量传递数据中获得热传递系数。尖端表面上的流动可视化是使用油点技术提供的。考虑了两种不同的刀头几何形状：一个在叶片的压力侧上具有小翼而在叶片的吸力侧上具有一个Squealer的Squealer尖端和小翼-Squealer尖端。在尖端间隙水平的测量值是实际弦的0.6％到3.6％。对于所有测量，基于实际和弦的出口雷诺数约为7.2 x 10〜5。流量可视化显示了叶片尖端表面上的撞击和再循环区域，从而提供了对传质分布的解释，并提供了对间隙内流体动力学的深入了解。对于两种尖端几何形状，尖端间隙水平对传质分布都有重要影响。尖叫器尖端的平均质量传递较高，随着间隙水平的升高而明显降低，而对于小翼挤压器尖端的平均质量传递，观察到的间隙水平变化更为有限。
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