Effect of an unsteady wake on the external heat transfer of 2nd stage rotor

A rotor blade is affected by the unsteady wake from the stator in the previous stage. An unsteady wake causes differences in the flow and heat transfer distribution on the external surface of the rotor blade. Therefore, the effect of unsteady wake should be studied for optimal design of blade cooling. To investigate the effect of an unsteady wake, this study measured the local heat transfer distribution over the entire external blade surface using the naphthalene sublimation method. Several rods moved across the inlet of the cascade to make the unsteady wake and the Strouhal number was varied from 0.0 to 0.3. The heat transfer on the entire pressure-side surface in an unsteady wake increases due to the high turbulence. The unsteady wake flow disturbs the developing passage vortex and tip leakage flow. As a result, the heat transfer near the endwall and tip surfaces in the unsteady wake case is lower than that in the steady case.