Effect of Density Ratio on Flat Plate Film Cooling With Shaped Holes Using PSP

Abstract

Detailed film-cooling effectiveness distributions are obtained on a flat plate using the pressure sensitive paint (PSP) technique. The applicability of the PSP technique is expanded to include a coolant-to-mainstream density ratio of 1.4. The effect of density ratio on the film-cooling effectiveness is coupled with varying blowing ratio (M=0.25–2.0), freestream turbulence intensity (Tu=1–12.5%), and film hole geometry. The effectiveness distributions are obtained on three separate flat plates containing either simple angle, cylindrical holes, simple angle, fanshaped holes (α=10 deg), or simple angle, laidback, fanshaped holes (α=10 deg and γ=10 deg). In all three cases, the film-cooling holes are angled at θ=35 deg from the mainstream flow. Using the PSP technique, the combined effects of blowing ratio, turbulence intensity, and density ratio are captured for each film-cooling geometry. The detailed film-cooling effectiveness distributions, for cylindrical holes, clearly show that the effectiveness at the lowest blowing ratio is enhanced at the lower density ratio (DR=1). However, as the blowing ratio increases, a transition occurs, leading to increased effectiveness with the elevated density ratio (DR=1.4). In addition, the PSP technique captures an upstream shift of the coolant jet reattachment point as the density ratio increases or the turbulence intensity increases (at moderate blowing ratios for cylindrical holes). With the decreased momentum of the shaped film-cooling holes, the greatest film-cooling effectiveness is obtained at the lower density ratio (DR=1.0) over the entire range of blowing ratios considered. In all cases, as the freestream turbulence intensity increases, the film effectiveness decreases; this effect is reduced as the blowing ratio increases for all three film hole configurations.

Film Cooling of Cylindrical Hole With a Downstream Short Crescent-Shaped Block

“…This mass transfer analogy technique is developed by Zhang and Jaiswal [20]. Since then, the PSP measurement technique has been widely applied to many film-cooling investigations [21][22][23][24][25]. PSP is a photoluminescent material that emits light when excited.…”

An Experimental Investigation of Showerhead Film Cooling Performance on a Turbine Blade

“…To characterize the film cooling, the adiabatic film cooling effectiveness was adopted and defined as aw c T T T T (4) where T ∞ is the mainstream temperature; T c is the secondary flow temperature; T aw is the laterally average adiabatic wall temperature on the outer blade surface in present study. The coefficient of total pressure penalty which was adopted to estimate the aerodynamic loss is defined as…”

“…As a kind of effective cooling technology, film cooling has been widely applied to maintain the blade temperature at acceptable levels. Numerous studies focused on film cooling have been performed for discussing the film cooling mechanism in the past decades, including the combined effects of mainstream turbulence intensity, coolant-to-mainstream blowing, density, and momentum ratio [2][3][4][5]. The classical kidney vortexes induced downstream of a cylindrical hole are proved to be the most important factor adversely influencing the film cooling effectiveness.…”

Validation of three dimensional film cooling modeling on convex surface for gas turbine blade

“…Wright et al [3] studied the effect of density ratio on flat plate film cooling. Three separate flat plates containing cylindrical holes, fan shaped holes and laidback fan shaped holes have been employed.…”