Effects of vane/blade relative positions and showerhead film cooling on a stationary blade: Heat transfer

The present study investigates the effects of relative position on heat transfer distributions of a showerhead film-cooled stationary rotor blade. Detailed heat/mass transfer coefficients were measured using the naphthalene sublimation method. A low-speed wind tunnel was used, with a single annular turbine stage consisting of sixteen guide vanes and blades. The axial chord length of the test blade was 136 mm. The inlet and exit angles of the test blade were 56.4° and -62.6°, respectively, which produced a turning angle of 119.0°. Three rows of film cooling holes were drilled in the leading edge region of the blade. Each row had 10 circular cooling holes along the spanwise direction, and the diameter of each cooling hole was 1.2 mm. Detailed heat transfer coefficients were measured at two different guide vane and rotor blade relative positions, while changing the blowing rate (M) from 1.0 to 2.0. The inlet Reynolds number was fixed at 1.3×10₅ based on the blade axial chord length. As the blowing rate increased, overall heat transfer rates increased, and the lower peaks formed on the pressure side by the separation bubble were reduced, and disappeared at M=2.0. The effects of vane/blade relative position were significant because the incoming flow condition was changed. However, the spanwise average Sherwood number became similar as the blowing rate increased.