Effects of Rib Design on the Unsteady Tip Heat Transfer Amplitude for a Turbine Rotor Blade

By solving the unsteady Reynolds-averaged Navier–Stokes equations and SST k–ω turbulence model, effects of rib design on the unsteady tip heat transfer amplitude for a turbine rotor blade with different rotating speeds are numerically investigated. The results of turbulence model validation are in good agreement with the experimental data. The grid independence verification is also satisfied. The results indicate that the averaged heat transfer coefficient of ribbed tip is 3.1% lower than that of traditional squealer tip and the amplitude of the heat transfer coefficient at the ribbed blade tip is 31.7% lower than that at the traditional squealer tip at standard speed condition. Low-energy passing wake causes the variation of flow field pressure near the tip clearance, which changes the strength of vortex such as pressure corner vortex, scratching vortex, leading edge vortex, and rib vortex inside the cavity, and thus causes the tip heat transfer coefficient fluctuation. At 85% standard speed, the average heat transfer coefficient amplitude of the ribbed tip is reduced by 35.4%. At 115% standard speed, the average heat transfer coefficient amplitude of the ribbed tip is reduced by 44.5%. Ribbed blade tip is suitable to reduce the heat transfer coefficient in turbine design