Correlative Analysis of Effusion Cooling Systems

Abstract

Gas turbine cooling has steadily acquired major importance whenever engine performances have to be improved. Among various cooling techniques, film cooling is probably one of the most diffused systems for protecting metal surfaces against hot gases in turbine stages and combustor liners. Most recent developments in hole manufacturing allow to perform a wide array of micro-holes, currently referred to as effusion cooling. This paper presents the validation of a simplified 2D conjugate approach through comparison with the experimental results of effectiveness for an effusion plate, performed during the first year of the European Specific Targeted REsearch Project AITEB-2 (Aerothermal Investigation of Turbine Endwalls and Blades). A preliminary test is performed with the steady-state technique, using TLC (Thermochromic Liquid Crystal) wide-band formulations. Results are obtained in terms of local distributions of adiabatic effectiveness. Average values are compared with calculations to validate the numerical code. Then, Design Of Experiment (DOE) approach is used to perform several conjugate tests (about 180), so as to derive the behavior of different effusion plates in terms of overall effectiveness and mass flow rate. Data are analyzed in detail and a correlative approach for the overall effectiveness is proposed.

Numerical Investigation of Effusion Cooling in Gas Turbine Combustor Liner

“…Scrittore [5] studied on a plate with cooling holes inclined by 30-degree, a L/D of 8.9, a Reynolds Number of 8600, blowing ratio of 3.2-5, a density ratio of 1, a coolant temperature of 300 K and a mainstream temperature of 330 K. Axial (x/D) and lateral (z/D) velocity profile flow characteristics were extracted from velocity measurements by Laser Doppler Velocimetry (LDV). Zhong [6] performed a numerical analysis on a ceramic plate with 23 and 90-degree inclined effusion cooling holes, a L/D of 8.6, a blowing ratios of 0.2-1, a density ratio of 1, a coolant temperature of 160 K and a mainstream temperature of 320 K. Arcangeli et al [7] studied on a plate with 30 and 90-degree inclined effusion cooling holes, a L/D of 10-43, a hole Reynolds Number of 6000, a blowing ratio of 0.3, a density ratio of 1, a coolant temperature of 300 K and a mainstream temperature of 325 K. That study is aimed to investigate how does L/D affect the cooling efficiency, keeping other factors constant. Cho et al [8] conducted a study on a plate with 90degree inclined cooling holes, a density ratio of 1.5, a Reynolds Number of 3200-14000, a coolant temperature of 300 K and a mainstream temperature of 350 K. The heat transfer coefficients were investigated in terms of staggered, shifted, and inline arrays and it was suggested that the staggered arrays outweighed the others.…”

Assessment of Numerical Tools for the Evaluation of the Acoustic Impedance of Multi-Perforated Plates

“…Common cooling systems, such as effusion and impingement are accomplished with a direct drilling of liner metal in the former case [3,4], and with a second external perforated plate which provide cool jets pointing the cold side of liner in the latter case.…”

Numerical investigation of the effectiveness of effusion cooling for plane multi-layer systems with different base-materials

“…They found that the cooling effectiveness increases asymptotically over a relatively high number of rows. A combined experimental and numerical paper by Arcangeli et al [12] indicates that the effectiveness increases with decreasing cooling hole diameter. Although an iterative conjugate-solver is used, the experimental and numerical results match well.…”