Control of the leakage flow and heat transfer characteristics at the blade tip by cavity filling

Abstract

In order to reduce leakage flow, cavity tips are often used in high-pressure turbines, at the cost of higher thermal load compared to flat tips. To better control the leakage flow and heat transfer at the blade tip, a cavity-filling geometry is proposed in this paper, and the effects of the filling area are also investigated by numerical simulation. The results indicate that the new geometries maintain the advantages of cavity tips in terms of aerodynamic performance. With the cavity filling area increasing, the heat transfer of the new geometries shows a trend of initially increasing and then decreasing. When the front 15% of the blade tip chord length is filled, the average heat transfer of this configuration is reduced by 3.7% compared to the cavity blade tip, and the high heat transfer area is reduced by 23.3%, at the cost of more intensive hot spots. As the cavity-filling area increases from 5% to 15%, the size of the vortexes at the cavity reduces, resulting in a rise in the leakage. Similar behaviors of the tip heat transfer and leakage flow were also found when the turbine pressure ratios varied from 3 to 7, with the cavity-filling geometry.