HEAT-TRANSFER COEFFICIENTS OVER A FLAT SURFACE WITH AIR AND CO2 INJECTION THROUGH COMPOUND ANGLE HOLES USING A TRANSIENT LIQUID-CRYSTAL IMAGE METHOD

This paper presents the detailed heat transfer coefficients over a fla t surface with one row of injection holes inclined streamwise at 35 de g for three blowing ratios (M = 0.5-2.0). Three compound angles of 0, 45, and 90 deg with air (D.R. = 0.98) and CO2 (D.R. = 1.46) as coolant s were tested at an elevated free-stream turbulence condition (Tu appr oximate to 8.5 percent). The experimental technique involves a liquid crystal coating on the test surface. Two related transient tests obtai ned detailed heat transfer coefficients and film effectiveness distrib utions. Heat transfer coefficients increase with increasing blowing ra tio for a constant density ratio, bur decrease with increasing density ratio for a constant blowing ratio. Hear transfer coefficients increa se for both coolants over the test surface as the compound angle incre ases from 0 to 90 deg. The detailed heat transfer coefficients obtaine d using the transient liquid crystal technique, particularly in the ne ar-hole region, will provide a better understanding of the film coolin g process in gas turbine components.