The steady and unsteady film cooling performance together with leakage flow and heat transfer characteristics for a typical gas turbine stage with a squealer tip is numerically investigated using the three-dimensional Reynolds-averaged Navier-Stokes(RANS)solutions. The influence of the film blowing ratio on the film cooling effectiveness in the squealer tip is discussed. The results calculated for the steady film cooling show that the film cooling effectiveness with a blowing ratio of 1.0 is greater than that of 0.5 or 1.5. However

the cooling gas will be separated at the adjacent downstream area of the film holes when the blowing ratio is 1.5. The results for the unsteady film cooling show that the flow and the film cooling effectiveness in the rotor squealer tip has significant unsteady characteristics under the interaction between the rotor/stator blade rows. The separation line at the bottom of the rotor squealer tip changes because the upstream wake and passage vortex interact periodically with the leakage flow in the rotor blade tip. The covering position and area of the film cooling vary accordingly. This unsteady flow behavior results in variation of the film cooling effectiveness at the bottom and sidewall of the rotor squealer tip. The film cooling effectiveness at the bottom of the rotor squealer tip achieved by the steady numerical prediction is greater than that by the unsteady numerical simulation.