COMBINED EFFECT OF GRID TURBULENCE AND UNSTEADY WAKE ON FILM EFFECTIVENESS AND HEAT-TRANSFER COEFFICIENT OF A GAS-TURBINE BLADE WITH AIR AND CO2 FILM INJECTION

Experiments were performed to study the combined effect of grid turbul ence and unsteady wake on film effectiveness and heat transfer coeffic ient of a turbine blade model. Tests were done on a Jive blade linear cascade at the chord Reynolds number of 3.0 x 10(5) at cascade inlet. Several combinations of turbulence grids, their locations,, and unstea dy wake strengths were used to generate various upstream turbulence co nditions The test blade had three rows of film holes in the leading ed ge region and two rows each on the pressure and suction surfaces. Air and CO2 were used as injectants. Results show that Nusselt numbers for a blade with film injection are much higher than that without film ho les. An increase in mainstream turbulence level causes an increase in Nusselt numbers and a decrease in film effectiveness over most of the blade surface, for both density injectants, and at all blowing ratios. A free-stream turbulence superimposed on an unsteady wake significant ly affects Nusselt numbers and film effectiveness compared with only a n unsteady wake condition.