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

Abstract

Abstract:The continuing rise in turbine entry temperatures has necessitated the development of ever-more advanced cooling techniques. Effusion cooling is an example of such a system and is characterised by a high density of film cooling holes that operate at low blowing ratios, thereby achieving high overall cooling effectiveness. This paper presents both an experimental and computational investigation into the cooling performance of effusion systems. Two flat-plate geometries (with primary hole pitches of 3.0D and 5.75D) are experimentally investigated via a pressure sensitive paint technique yielding high resolution film effectiveness distributions via heat-mass transfer analogy. A computational fluid dynamics (CFD) scalar tracking method was used to model the setup computationally with the results comparing favourably to those obtained from the experiments. The CFD domain was modified to assess the cooling performance from a single film hole ejection. A superposition method was developed and applied to the resulting two-dimensional film effectiveness distribution that quickly yielded data for an array of closely-packed holes, allowing a rapid assessment of a multi-hole effusion type setup. The method produced satisfactory results at higher pitches, but at lower pitches, high levels of jet interactions reduced the performance of the superposition method.

Influence of Spanwise and Streamwise Film Hole Spacing on Adiabatic Film Effectiveness for Effusion-Cooled Gas Turbine Blades

“…Experiments by Muska et al [11] and more recently Murray et al [12] reaffirm the superposition method and its usefulness in predicting multi-row film cooling. The latter used a modified Goldstein Equation [13] (described later, but in the form of Equation ( 3)) to predict the film distribution of an individual hole and, when combined with Sellers' superposition, found the additive effect of multiple film hole rows.…”

“…The spanwise distance constant (c 1 ) and the spanwise shaping constant (c 2 ), which influence the spanwise film decay, are variables dependent on both the blowing ratio M and distance downstream of the film hole x. The values for these are based on experimental and correlation data, which can be found in [12,17].…”

Experiments of Transpiration Cooling Inspired Panel Cooling on a Turbine Blade Yielding Film Effectiveness Levels over 95%

“…Several studies have demonstrated the film effectiveness of arrays of more tightly packed holes and porous media, albeit on flat plates. In a study by Murray et al [4], the effect of hole pitch of effusion cooled plates demonstrated that the for a given coolant output per unit area, reducing the pitch between coolant holes greatly improved the average film effectiveness of the studied plate. Reducing the pitch to hole diameter ratio from 5.75 to 3 more than doubled the effectiveness.…”

Nonlinear Optimization of Turbine Conjugate Heat Transfer with Iterative Machine Learning and Training Sample Replacement

“…Most of the time, knowledge learnt from one setting could not be scaled for other operating situations or a simple addition of effects did not work. Murray et al [7] discussed effusion cooling as an example of stitching together multiple smaller film holes. It was characterized by a high density of smaller diameter film cooling holes operating at low blowing ratios with higher overall cooling effectiveness.…”