Experimental and Numerical Study of the Turbulent Flow and Heat Transfer in a Wedge-shaped Channel with Guiding Pin Fin Arrays under Rotating Conditions

Experiments and numerical simulations under stationary and rotating conditions have been conducted to investigate turbulent flow and heat transfer characteristics of innovative guiding pin fin arrays in a wedge-shaped channel, which models the internal cooling passages for gas turbine blade trailing edge. The Reynolds number range is 10,000-80,000, and the inlet rotation number range is 0-0.46. With the increase of Reynolds numbers, the enhancement of heat transfer performance with guiding pin fin arrays is significantly higher than that with conventional circular pin fin arrays. At the highest Reynolds number of Re=80,000, the overall Nusselt number of the channel with guiding pin fin arrays is about 33.7% higher than that of the channel with circular pin fin arrays under the stationary condition, and is about 23.0% higher than the latter under the rotating conditions. At the highest inlet rotation number of Ro=0.46, the heat transfer difference between the trailing side and leading side of the channel is significantly lower with the guiding pin fin arrays. Both the experiments and numerical simulations indicate that the heat transfer uniformity and enhancement of the channel endwall is significantly improved by the guiding pin fin arrays under stationary and rotating conditions, which provide more reasonable flow distribution in the wedge-shaped channel, and can further produce obviously improved heat transfer in the tip region for the trailing edge internal cooling channel.

Delayed-Detached Eddy Simulations of Film Cooling Effect On Trailing Edge Cutback with Land Extensions

Film cooling effect on trailing edge cutback with land extensions (i.e. landed case) was numerically investigated with the Delayed-Detached Eddy Simulation method. At three rib geometries (i.e. in-line rib arrays, six-row pin-fin arrays, and five-row pin-fin arrays) and five blowing ratios (i.e. M=0.5, 0.8, 1.1, 1.5 and 2.0), film cooing effectiveness, coherent vortex structures and discharge coefficients for the landed cases were analyzed and compared with baseline cases (i.e. cutback without land extensions). The results show that land extensions have significant influences on coherent flow structures, vortex energy levels, film cooling effectiveness, and discharge coefficients in cutback region. Different from the baseline cases, the dominant vortex structures in landed cases exhibit the "double helix" (for cutback with in-line rib array) or "strip" pattern (for cutback with pin-fin arrays), and the thickness of mixing region in landed cases is decreased. Among three rib geometries, the trailing edge cutback with six-row pin fin arrays has the worst cooling effect for both baseline and landed cases. Compared with the baseline cases, the discharge coefficients for the landed cases are decreased by about 21.4%. With land extensions, the overall film cooling effectiveness on cutback is decreased firstly and then increased with increasing blowing ratio. Among all investigated cases, cutback with five-row pin fin arrays for the landed case performs the best film cooling effect at M=0.5.