Heat Transfer Enhancement in a Rotating Wedge-Shaped Cooling Channel With Optimized Detached Guiding Pin-Fin

Abstract

Experiments and numerical simulations are conducted to investigate the flow and heat transfer characteristics of the guiding pin-fin array in a rotating wedge-shaped channel that represents the internal cooling passage features for turbine blade trailing edges. The rotating experiments cover Reynolds number ranges from 10,000 to 80,000 and rotation number ranges from 0 to 0.46. The results demonstrate that, with a proper arrangement, the guiding pin-fin array can significantly reduce the endwall temperature and pressure loss in the wedge-shaped channel. However, it was observed that at the midspan of the guiding pin-fin array channel, heat transfer was relatively low, forming a high-temperature region. To enhance channel heat transfer uniformity, 2 mm clearances were introduced to the guiding pin-fins at the channel root region, 2 mm from the trailing endwall. The numerical results show that this structural modification effectively improved the endwall heat transfer intensity at the midspan of the wedge-shaped channel, particularly on the leading surface. In cases with Reynolds number (Re) equal to 50,000 and rotation number (Ro) equal to 0.075, the leading and trailing endwall Nusselt numbers of the detached guiding pin-fin array were 6.5% and 4.8% higher than those of the guiding pin-fin array. The secondary flow and transverse vortex induced by the detached pin-fins reduced the main stream velocity, thereby inhibiting the Coriolis force effect and diminishing the endwall heat transfer discrepancy. Further comparisons at Re = 50,000 and Ro = 0.075 and 0.15 revealed that the leading and trailing endwall heat transfer discrepancy coefficient (δ) of the detached guiding pin-fin array was 61.8% and 42.2% lower than that of the circular pin-fin array, respectively. In high-temperature cases with solid domain, which are closer to the real turbine blade operating condition, the detached guiding pin-fin array also can provide superior cooling performance. In the wedge-shaped channel with detached guiding pin-fin, the maximum and average temperature values of the solid domain are about 10% lower than that of the channel with circular pin-fin, at both rotating and stationary conditions.