Experimental impingement heat transfer in a smooth channel with cross over jets and bleed holes

• Online Access: http://hdl.handle.net/2047/d20000061

Trailing edge cooling cavities in modern gas turbine airfoils play an important role in maintaining the trailing edge temperature at levels consistent with airfoil design life. These cavities often have a trapezoidal cross-sectional shape in order to be compatible with the external contour of the blade at the trailing edge. The cooling flow for these geometries generally enters the trailing edge cavity from the adjacent cavity through a row of race-track shaped slots with mounted holes on the partition wall between the two cavities. Cross-over jets, impinge on a smooth trailing-edge wall and exit through the second row of race-track shaped slots. Steady state liquid crystal technique is used in this experimental investigation to measure the impingement heat transfer coefficients on the smooth surface of the trapezoidal channel. The experimental setups were arranged for zero- and five-degree tilt angle for the cross-over jets with zero, two and four blocked consecutive slots along the trailing-edge. Tests were performed for two inlet and exit slot arrangements - staggered and inline. These setups were investigated over a range of Reynolds number. The results showed that the Nusselt numbers increase monotonically with increasing Reynolds numbers. Pressure ratio (Psupply/Ptrailing-edge) increased with increasing Reynolds numbers. The four-blocked consecutive holes along the trailing-edge induced higher pressure ratios than the cases where all exit holes were opened. Heat transfer coefficients decreased significantly near the blocked slots while the cross flow created by the blockage of the exit slots increased the heat transfer coefficients near the open slots.