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Research Papers: Gas Turbines: Heat Transfer

# Numerical Study of Aerodynamic Losses of Effusion Cooling Holes in Aero-Engine Combustor Liners

[+] Author and Article Information
A. Andreini

Dipartimento di Energetica “Sergio Stecco”, University of Florence–Italy, Via Santa Marta 3, 50139 Florence, Italyantonio.andreini@htc.de.unifi.it

A. Bonini, G. Caciolli, B. Facchini

Dipartimento di Energetica “Sergio Stecco”, University of Florence–Italy, Via Santa Marta 3, 50139 Florence, Italy

Combustion System, AVIO Group S.p.A., 10040 Rivalta (TO), Italysimone.taddei@aviogroup.com

J. Eng. Gas Turbines Power 133(2), 021901 (Oct 29, 2010) (10 pages) doi:10.1115/1.4002040 History: Received May 04, 2010; Revised May 28, 2010; Published October 29, 2010; Online October 29, 2010

## Abstract

Due to the stringent cooling requirements of novel aero-engines combustor liners, a comprehensive understanding of the phenomena concerning the interaction of hot gases with typical coolant jets plays a major role in the design of efficient cooling systems. In this work, an aerodynamic analysis of the effusion cooling system of an aero-engine combustor liner was performed; the aim was the definition of a correlation for the discharge coefficient $(CD)$ of the single effusion hole. The data were taken from a set of CFD RANS (Reynolds-averaged Navier-Stokes) simulations, in which the behavior of the effusion cooling system was investigated over a wide range of thermo/fluid-dynamics conditions. In some of these tests, the influence on the effusion flow of an additional air bleeding port was taken into account, making it possible to analyze its effects on effusion holes $CD$. An in depth analysis of the numerical data set has pointed out the opportunity of an efficient reduction through the ratio of the annulus and the hole Reynolds numbers: The dependence of the discharge coefficients from this parameter is roughly linear. The correlation was included in an in-house one-dimensional thermo/fluid network solver, and its results were compared with CFD data. An overall good agreement of pressure and mass flow rate distributions was observed. The main source of inaccuracy was observed in the case of relevant air bleed mass flow rates due to the inherent three-dimensional behavior of the flow close to bleed opening. An additional comparison with experimental data was performed in order to improve the confidence in the accuracy of the correlation: Within the validity range of pressure ratios in which the correlation is defined $(>1.02)$, this comparison pointed out a good reliability in the prediction of discharge coefficients. An approach to model air bleeding was then proposed, with the assessment of its impact on liner wall temperature prediction.

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## Figures

Figure 1

Scheme of the cooling system

Figure 2

Reference sections for the evaluation of CD

Figure 3

Single hole validation test case: sketch of the computational domain; mesh detail

Figure 4

Single hole validation test case: comparison between experimental (6) and numerical values of CD

Figure 5

Sketch of the computational domain: (a) boundary conditions and (b) computational mesh

Figure 6

Trend of the discharge coefficients; no_bleed: (a) outer annulus and (b) inner annulus; bleed: (c) outer annulus and (d) inner annulus

Figure 7

Discharge coefficients versus Reynolds ratio; no_bleed: (a) outer annulus and (b) inner annulus; bleed: (c) outer annulus and (d) inner annulus

Figure 8

Relative errors between CD predicted and extracted from CFD

Figure 9

No_bleed, case engine: comparisons between the correlation and the values extracted from CFD; (a) outer annulus and (b) inner annulus

Figure 10

Bleed, case cruise: comparisons between the correlation and the values extracted from CFD; (a) outer annulus and (b) inner annulus

Figure 11

The two models for the bleeding system: (a) previous model and (b) new model

Figure 12

Annulus mass flow: comparisons between different models: (a) outer annulus and (b) inner annulus

Figure 13

No_bleed, case engine: comparisons between the CFD, the correlation and values predicted by SRBC; (a) outer annulus and (b) inner annulus

Figure 14

Bleed, case cruise: comparisons between the CFD, the correlation and values predicted by SRBC; (a) outer annulus and (b) inner annulus

Figure 15

Comparison between experiments and numerical results

Figure 16

Temperature profile along the inner liner

Figure 17

Nusselt number along the inner liner

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