Local Mass and Heat Transfer on a Turbine Blade Tip

P Jin,R J Goldstein

doi:10.1155/s1023621x03000083

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 ×105) 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.

Highlights

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 dots in the figure are the positions at which the measurements took place, and they are aligned in lines parallel to the y/C direction
The experiments were conducted in a linear cascade consisting of five highpressure blades with tip clearances

Summary

Introduction

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. Experimental studies have already been conducted to understand the tip leakage flow in turbine cascades, including flow visualization and measurement of static pressure and loss coefficients inside the tip clearance and blade passage in turbine cascades (Bindon, 1987; Kang and Hirsch, 1993; Moore and Tilton, 1988; Sjolander and Amrud, 1987; Yamamoto, 1988). Though the effects of tip leakage flow on turbine blade heat transfer have been investigated, most studies have been conducted in idealized experimental conditions (on a flat plate or in rectangular cavities). Not many detailed local heat-transfer measurements on turbine blade tip surfaces and near-tip surfaces are available in the open literature

Methods

Results

Conclusion