Energy and Power En gi neering, 2011, 3, 607-615

doi:10.4236/epe.2011.35076 Published Online November 2011 (http://www.SciRP.org/journal/epe)

Copyright © 2011 SciRes. EPE

RANS and LES Modeling of the GE10 Burner

Vladimir L. Zimont1, Vincent Moreu1, Valerio Battaglia1, Roberto Modi2

1CRS4, Science and Technology Park Polaris, Pula, Italy

2GE Oil & Gas Nuovo Pignone, Florence, Italy

E-mail: {zimont, moreau}@crs4.it, roberto.modi@ge.com

Recieved April 28, 2011; revised May 29, 2011; acce p ted June 10, 2011

Abstract

The paper presents 1) the numerical results of RANS (Reynolds Averaging Navier-Stokes) simulations for

two versions of the premixed combustion GE10 burners: the old one with non-premixed and modified one

with swirled premixed pilot flames; and 2) the numerical results of joint RANS/LES (Large Eddy Simula-

tion) modelling of the ONERA model burner and a simplified GE10 combustor. The original joint

RANS/LES approach is based on using the Kolmogorov theory for modelling sub-grid turbulence and com-

bustion intensity and using RANS numerical results for closure the LES model equations. The main conclu-

sion is that developed joint RANS/LES approch is the efficient timesaving tool for simulations both the av-

erage and instantaneous fields of parameters in gas turbine and boiler burners with premixed combustion.

Keywords: Turbulent Premixed Combustion, Gas Turbine Burner, Joint RANS/LES Simulation

1. Introduction

The proposed work is devoted to lean premixed combus-

tion technology, which is nowadays well established

within industrial gas turbine industry in order to reduce

nitric oxides (NOx) emission. The main numerical mod-

eling tool for industrial gas turbine combustion is RANS

codes, which yield averaged fields and integral charac-

teristics of the flow. The main part of this presentation is

devoted to RANS simulations of two variants of the

GE10 gas turbine combustor, which include 1) simula-

tions of the premixed combustion in the chamber; 2)

simulations of the preliminary partial mixing of gas fuel

and air; 3) simulations of the non-premixed pilot flame

(old version GE10); 4) premixed pilot flame (new ver-

sion GE10); and 5) air jets cooling system of the cham-

ber. In conditions of industrial gas turbines, instanttane-

ous combustion takes place in non-laminar (microturbu-

lent) and strongly wrinkled sheets with small-scale

structure, which fundamentally cannot be resolved by

model RANS and LES equations. In the presented simu-

lations, we used our Turbulent Flame Closure (TFC)

model [1-3], where this fundamental problem of model-

ing (“challenge of turbulent combustion”) is resolved in

the context of the Kolmogorov hypothesis of statistical

equilibrium of small-scale turbulent structures general-

ized for the case of turbulent combustion. This model

was already used for RANS simulations of the gas tur-

bine combustion and these results where presented in

IGTACE, Florida, 1997 (97-GT-395) published in [4]

and JPGC, 2001 [5]. (This mode l is now implemented in

the commercial codes Fluent and CFX.)

RANS results are important but not sufficient as non-

stationary characteristics of the flow are also important

in gas turbine applications. In academicals works, an

attempt to replace RANS tool by LES one is ongoing.

We think that “LES instead of RANS” in industrial ap-

plication is untimely and we proposed in [6] a joint

RANS/LES approach where the mean fields are simu-

lated by the RANS tool while the corresponding non-

stationary fields are simulated by the LES one using for

modeling some information from the preceding RANS

simulation. The paper [6 ] contains numerical illustrations

of this approach concerning mainly “academic” flames.

We achieved agreement between RANS and LES sub-

problems by using in fact the same combustion models in

both sub-problems. In this paper, we present numerical

results in the context of the joint RANS/LES approach

for gas turbine com b us tors.

We found support to our approach in the invited lec-

ture [7]. In the conclusions, the authors write: “The fu-

ture tools for gas turbine designs will be based on classi-

cal Reynolds Averages codes to predict main flows but

will also rely on Large Eddy Simulation tools coupled to

acoustic codes” (in our example both RANS and LES

sub-problems were stated in incompressible formulation).