Numerical Study of Film-Cooling Performance on a Rotating Model

Flow characteristics, adiabatic effectiveness, and discharge-coefficient distributions are numerically investigated on a rotating film-cooling model under different operating conditions. The computational model originates from the midspan section of a typical turbine rotor with two rows of 14 staggered injection holes angled at 30, 60, and 90 deg, on both the suction surface and pressure surface, and the flow through the coolant plenum and all of the hole pipes are resolved as a part of the computational domain by specifying the coolant mass flux in the plenum. The commercial computational fluid dynamics code Star-CD with structured body-fitted grids is employed for the computations, and the Wilcox -! model is chosen for turbulence closure. In the present study, the Reynolds number Re based on mainstream velocity and injection-hole diameter varies from 1835 to 5507, and the averaged blowing ratio M ranges from 0.5 to 1.5. Results show that the coolant will move to the high-radius locations near the suction and pressure surfaces due to the strong centrifugal effect, which leads to the decrease in adiabatic effectiveness accordingly. The discharge coefficients Cd on the pressure surface are much higher than those on the suction surface under a given operating condition. In addition, the critical values of angular speed that represent the equilibrium of centrifugal force and Coriolis force near the pressure surface are also presented in this paper.