Studies on Wake-Affected Heat Transfer Around the Circular Leading Edge of Blunt Body

Abstract

Detailed measurements are performed about time-averaged heat transfer distributions around the leading edge of a blunt body, which is affected by incoming periodic wakes from the upstream moving bars. The blunt body is a test model of a front portion of a turbine blade in gas turbines and consists of a semicircular cylindrical leading edge and a flat plate afterbody. A wide range of the steady and unsteady flow conditions are adopted as for the Reynolds number based on the diameter of the leading edge and the bar-passing Strouhal number. The measured heat transfer distributions indicate that the wakes passing over the leading edge cause a significant increase in heat transfer before the separation and the higher Strouhal number results in higher heat transfer. From this experiment, a correlation for the heat transfer enhancement around the leading edge due to the periodic wakes is deduced as a function of the Stanton number and it is reviewed by comparison with the other experimental works.

Effect of Periodic Wake Passing on Film Effectiveness of Discrete Cooling Holes Around the Leading Edge of a Blunt Body

“…1. This apparatus is almost the same with one used in previous heat transfer test by Funazaki (1996), except for the secondary air supply system. The main flow rate is adjusted by the inlet valve of the blower.…”

“…Pressure distributions around the test model are obtained using the test model of the same dimensions with the present one except for cooling holes, as had been employed by Funazaki (1996). Local flow velocity t/ ]ocal is then determined from those data.…”

“…Recently, Funazaki (1996) studied the influence of periodically passing wakes on the heat transfer over the leading edge as well as the flat plate. Local heat transfer distributions along the test surface were measured under the several unsteady conditions of bar-passing Strouhal number for four inlet Reynolds numbers.…”

“…Using this correlation, his study yielded similar results to those of the previous studies concerning the wake effect, despite the large difference in the geometrical conditions. This study focuses on the effect of periodic passing wakes on the leading edge film cooling under several free-stream turbulence conditions using a blunt body with semi-circular leading edge and flat afterbody, which is similar to that of Mehendale et al (1992) or Funazaki (1996). The present study is aimed at the investigation of the leading edge cooling effectiveness for turbine rotor blades or for stationary blades in the second or subsequent stages.…”

Heat transfer on a radially rotating heated cylinder

“…Magari and Lagraff [10] measured the heat transfer in the stagnation region of a cylinder over a range of Mach number, Reynolds number, and free-stream turbulence intensity. Funazaki [11] measured the time-averaged heat transfer distributions around the leading edge of a blunt body, under the influence of incoming periodic wakes. He found that the wakes passing over the leading edge cause a significant increase in heat transfer before flow separation.…”