Adiabatic Effectiveness and Heat Transfer Coefficient of Shaped Film Cooling Holes on a Scaled Guide Vane Pressure Side Model

Abstract

The demand of improved thermal efficiency and high power output of modern gas turbine engines leads to extremely high turbine inlet temperature and pressure ratios. Sophisticated cooling schemes including film cooling are widely used to protect the vanes and blades of the first stages from failure and to achieve high component lifetimes. In film cooling applications, injection from discrete holes is commonly used to generate a coolant film on the blade's surface. In the present experimental study, the film cooling performance in terms of the adiabatic film cooling effectiveness and the heat transfer coefficient of two different injection configurations are investigated. Measurements have been made using a single row of fanshaped holes and a double row of cylindrical holes in staggered arrangement. A scaled test model was designed in order to simulate a realistic distribution of Reynolds number and acceleration parameter along the pressure side surface of an actual turbine guide vane. An infrared thermography measurement system is used to determine highly resolved distribution of the models surface temperature. An in-situ calibration procedure is applied using single embedded thermocouples inside the measuring plate in order to acquire accurate local temperature data. All holes are inclined 35 • with respect to the model's surface and are oriented in a streamwise direction with no compound angle applied. During the measurements, the influence of blowing ratio and mainstream turbulence level on the adiabatic film cooling effectiveness and heat transfer coefficient is investigated for both of the injection configurations.

Film cooling sensitivity of laidback fanshape holes to variations in exit configuration and mainstream turbulence intensity

“…10 and 11. According to the analysis in previous studies [15,19] which the authors agree with, this ''fork tines'' pattern of enhanced heat transfer is caused by the counter-rotating vortex pair shown in Fig. 8 which could thicken the boundary layer in the centerline region of film jet and thin the boundary layer at the lateral edges of the film jet.…”

“…[11][12][13][14][15][16]. Guo et al [11] found that fanshape holes produced higher cooling effectiveness and lower heat transfer coefficient than cylindrical holes on both suction and pressure side of a nozzle vane model in a transonic annular cascade.…”

“…The two shaped holes had higher cooling effectiveness and lower heat transfer coefficient than the cylindrical holes. Dittmar et al [15] found that single row of fanshape holes produced better thermal protection than double-row of cylindrical holes at high blowing ratios on the vane pressure side. Gao et al [16] performed experimental tests on a high pressure turbine blade model with laidback fanshape holes.…”

The effect of turbulence intensity on film cooling of gas turbine blade from trenched shaped holes

“…However, they reported that further increase in the blowing ratio results in a reverse effect. Dittmar et al [8] measured adiabatic film cooling effectiveness and the heat transfer coefficient of single row of fan shaped holes and a double row of cylindrical holes in staggered arrangement. During their measurements, the influence of blowing ratio and mainstream turbulence level on the adiabatic film cooling effectiveness and heat transfer coefficient is investigated for both of the injection configurations.…”