Film Cooling for Cylindrical and Fan-Shaped Holes Using Pressure-Sensitive Paint Measurement Technique

Abstract

A systematic study was performed to investigate the combined effects of film-hole geometry, blowing ratio, density ratio, and freestream turbulence intensity on a flat-plate film cooling. Detailed film-cooling effectiveness was obtained using a pressure-sensitive-paint technique. Four common geometries were used in this study: simple-angled cylindrical and fan-shaped holes, and compound-angled (β 45 deg) cylindrical and fan-shaped holes. Each plate contained one row with seven holes, and the hole diameter D and hole-length-to-diameter ratio (L∕D) are 4 mm and 7.5, respectively. The effects of the blowing ratio M, coolant-to-mainstream-density ratio DR, and freestream turbulence intensity Tu were tested within the ranges of 0.3 ∼ 2.0, 1.0 ∼ 2.0, and 0.5 ∼ 6%, correspondingly. Detailed variations of the laterally averaged effectiveness from low to high blowing ratios were obtained for three density ratios. The results indicated that effectiveness increased as increasing density ratio in general for all geometries. Fanshaped holes outweighed cylindrical ones in effectiveness at higher blowing ratios. An additional compound-angle enhanced effectiveness for cylindrical holes. For increasing turbulence intensity, effectiveness decreased for shaped holes but slightly increased for cylindrical ones. The experimental data of simple-angled fan-shaped holes were validated with empirical correlation limited to DR 1.7 ∼ 2.0, and an improved correlation was proposed to predict effectiveness at DR 1.0 ∼ 2.0. NomenclatureAR = area ratio of hole exit and inlet D = diameter of film-cooling hole, mm DR = coolant to mainstream density ratio; ρ c ∕ρ m M = blowing ratio; ρ c v c ∕ρ m v m P = pitch between adjacent holes, mm t = width of hole at trailing edge of hole breakout x = distance from trailing edge of holes, mm α = axial angle to the mainstream, deg β = compound angle to the mainstream, deg η = film-cooling effectiveness η ave = laterally averaged film-cooling effectiveness v = velocity, m∕s ξ = distance scaling parameter used in correlation ρ = density, kg∕m 3 Subscripts air = property with air injection blk = black condition c = coolant f = film fg = property with foreign gas injection m = mainstream ref = reference condition w = wall ∞ = mainstream property

An LBM-Based Investigation on the Mixing Mechanism of Double Rows Film Cooling with the Combination of Forward and Backward Jets

“…In this section, the validation of the numerical method is conducted before being adapted in the following simulations. The in-house STLBM-LES-GPUs code is validated by comparing the time-averaged temperature field with the experimental data of film cooling with cylindrical holes obtained by Chen et al [35]. The numerical results of spanwiseaveraged film cooling effectiveness with blowing ratio of 0.3 and inclination angle of 30 • have been compared with the experimental data, which is shown in Figure 3.…”

Effect of Mainstream Velocity on the Optimization of a Fan-Shaped Film-Cooling Hole on a Flat Plate

“…In general, when PSP is irradiated by light with a short wavelength (about 400 nm), it emits long-wavelength light (>600 nm) and returns to a ground state. The intensity of the light emission depends on the partial pressure of the oxygen, and the FCE can be obtained by using the characteristics of PSP [18,19]. The uncertainty of the measured FCE was estimated as ±7.7% at η = 0.3 and ±1.3% at η = 0.7.…”

Endwall film cooling holes design upstream of the leading edge of a turbine vane

“…Effects of the hole length-to-diameter ratio [27] and pitch-to-diameter ratio [28] have been considered in some previous research works. In the recent years, more research works [29] are concentrated on shaped holes to increase the cooling effectiveness, such as fan-shaped holes, which have exhibited higher effectiveness compared with normal cylindrical holes at higher BRs.…”