Measurement and Prediction of Adiabatic Film Effectiveness of Combustor Representative Effusion Arrays

Abstract

Thermal protection of gas turbine combustors relies heavily upon the delivery of a carefully managed film of coolant air to the hot-side of the combustor liner. Furthermore, improvements in engine sfc and the trend to ever more aggressive engine cycles means greater emphasis is being placed upon more efficient use of the proportion of combustion system air made available for cooling. As a result, there is a requirement to better understand the development of cooling films deposited onto the hot-side of the liner through complex effusion arrays. This study, therefore, is concerned with the prediction and measurement of adiabatic film effectiveness of a number of engine-representative designs. A RANS based CFD approach is used to predict film effectiveness in which computational cost is minimised by solving first for a single coolant passage to provide high fidelity, near-exit boundary conditions to the effusion arrays. Equivalent measurements are made for each test case using a Pressure Sensitive Paint (PSP) technique in which the oxygen-quenched fluorescence properties of the paint are employed together with a Nitrogen gas cooling simulant to determine adiabatic film effectiveness. This study demonstrates that whist the model under-predicts the mixing of the coolant with the main-stream flow, and hence the film development over the surface, the approach works well at quantifying the relative performance of each design.

Effectiveness Measurements of Additively Manufactured Film Cooling Holes

“…This approach to product development allows for several iterations in the same amount of time it takes to produce a single prototype with conventional casting methods. Krawciw et al [14] used L-PBF to create a panel with arrays of various shaped film cooling holes. They measured adiabatic effectiveness to evaluate performance of the array of film cooling holes.…”

High Resolution Experimental and Computational Methods for Modelling Multiple Row Effusion Cooling Performance

“…For similar reasons, effusion holes are often inclined to the blade surface direction, typically at around 30-35 • [9]. Krawciw et al [10] performed an experimental and computational study investigating the variation in film performance between an inclined cylindrical film hole and two fanned hole geometries, demonstrating the anticipated improvement in film effectiveness attributed to lateral jet spreading in the fanned geometries. Hu and Ji [11] performed a conjugate CFD study investigating the effect of varying inclination angle on cooling effectiveness and observed little variation in film performance between 30 • and 60 • inclined cylindrical holes.…”

Hybrid LES-RANS study of an effusion cooling array with circular holes

“…al. [15,16] assessing the performance of full coverage effusion cooling array configurations at scaled combustor conditions. In the former work, a jet-in-crossflow type turbulence generator was built to generate combustor relevant flow conditions with high intensity levels and large lengthscales.…”

“…This is mainly due to the diffusion of the coolant at hole exit which keeps the coolant jet attached to the plate surface at BRs up to 5. Krawciw [15,16] extended the work further to different hole geometries ranging from the most simple inclined cylindrical hole to more exotic helical hole. The cooling performance of those designs were examined by both the ACE in [15,16] using a Pressure-Sensitive-Pain (PSP) technique and the overall cooling effectiveness (OCE) accounting the heat conduction inside the effusion-cooled plate in [16] using the Infra-Red Thermography.…”

“…Krawciw [15,16] extended the work further to different hole geometries ranging from the most simple inclined cylindrical hole to more exotic helical hole. The cooling performance of those designs were examined by both the ACE in [15,16] using a Pressure-Sensitive-Pain (PSP) technique and the overall cooling effectiveness (OCE) accounting the heat conduction inside the effusion-cooled plate in [16] using the Infra-Red Thermography. The experiments in [15] were conducted at momentum ratios (M R) ranging from 0.6 to 15.…”