Local Mass and Heat Transfer on a Turbine Blade Tip

Abstract

Local mass and heat transfer measurements on a simulated high‐pressure turbine blade‐tip surface are conducted in a linear cascade with a nonmoving tip endwall, using a naphthalene sublimation technique. The effects of tip clearance (0.86–6.90% of chord) are investigated at various exit Reynolds numbers (4–7 × 10 5 ) and turbulence intensities (0.2 and 12.0%). The mass transfer on the tip surface is significant along its pressure edge at the smallest tip clearance. At the two largest tip clearances, the separation bubble on the tip surface can cover the whole width of the tip on the second half of the tip surface. The average mass‐transfer rate is highest at a tip clearance of 1.72% of chord. The average mass‐transfer rate on the tip surface is four and six times as high as on the suction and the pressure surface, respectively. A high mainstream turbulence level of 12.0% reduces average mass‐transfer rates on the tip surface, while the higher mainstream Reynolds number generates higher local and average mass‐transfer rates on the tip surface.