Abstract

The compressors of power-generation gas turbines (GTs) have a high stage count, blades with low aspect ratios, and large clearances. These features promote strong secondary flows. An important outcome deriving from the convection of intense secondary flows is the enhanced span-wise transport of fluid properties mainly involving the rear stages, generally referred to as “radial mixing.” An incorrect prediction of this key phenomenon may result in inaccurate performance evaluation and could mislead designers. In the rear compressor stages, the stream-wise vorticity associated with tip clearance flows is one of the main drivers of the span-wise transport phenomenon. Limiting it by averaging the flow at row interfaces is the reason why a steady analysis underpredicts radial mixing. To properly forecast the span-wise transport, an unsteady analysis should be adopted. However, this approach has a computational cost not yet suitable for industrial purposes. Currently, only the steady simulation can fit in a lean design chain and any model upgrade improving its radial mixing prediction would be highly beneficial. To attain some progresses in Reynolds-averaged Navier–Stokes (RANS) model, its lack of convection of stream-wise vorticity must be addressed. This can be done by acting on another mixing driver that is turbulent diffusion; by enhancing turbulent viscosity, one can promote span-wise diffusion, thus improving the radial mixing prediction. In this paper, this strategy to update the RANS model and its application on an existing compressor is presented, together with the model tuning that has been performed using unsteady results as the target.

References

References
1.
Weatheritt
,
J.
, and
Sandberg
,
R.
,
2016
, “
A Novel Evolutionary Algorithm Applied to Algebraic Modifications of the RANS Stress-Strain Relationship
,”
J. Comput. Phys.
,
325
, pp.
22
37
. 10.1016/j.jcp.2016.08.015
2.
Akolekar
,
H. D.
,
Weatheritt
,
J.
,
Hutchins
,
N.
,
Sandberg
,
R. D.
,
Laskowski
,
G.
, and
Michelassi
,
V.
,
2018
, “
Development and Use of Machine-Learnt Algebraic Reynolds Stress Models for Enhanced Prediction of Wake Mixing in Low Pressure Turbines
,”
Proceedings of ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition
,
Lillestrøm, Oslo, Norway
,
June 11–15
, Paper No. GT2018-75447, V02CT42A009, pp.
1
13
.
3.
Saito
,
S.
,
Yamada
,
K.
,
Furukawa
,
M.
,
Watanabe
,
K.
,
Matsuoka
,
A.
, and
Niwa
,
N.
,
2018
, “
Flow Structure and Unsteady Behavior of Hub-Corner Separation in a Stator Cascade of a Multi-Stage Transonic Axial Compressor
,”
Proceedings of ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition
,
Lillestrøm, Oslo, Norway
,
June 11–15
, Paper No. GT2018-76480, V02AT39A030, pp.
1
11
.
4.
Denton
,
J. D.
,
2010
, “
Some Limitations of Turbomachinery CFD
,”
ASME Turbo Expo 2010
, Paper No. GT2010-22540,
Glasgow, UK
.
5.
Cozzi
,
L.
,
Rubechini
,
F.
,
Giovannini
,
M.
,
Marconcini
,
M.
,
Arnone
,
A.
,
Schneider
,
A.
, and
Astrua
,
P.
,
2018
, “
Capturing Radial Mixing in Axial Compressors With CFD
,”
Proceedings of ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition
,
Lillestrøm, Oslo, Norway
,
June 11–15
, Paper No. GT2018-75942, V02CT42A025, pp.
1
11
.
6.
Wennerstrom
,
A. J.
,
1991
, “
A Review of Predictive Efforts for Transport Phenomena in Axial Flow Compressors
,”
ASME J. Turbomach.
,
113
(
2
), pp.
175
179
. 10.1115/1.2929080
7.
Leylek
,
J. H.
, and
Wisler
,
D. C.
,
1991
, “
Mixing in Axial-Flow Compressors: Conclusions Drawn from 3-D Navier-Stokes Analyses and Experiments
,”
ASME J. Turbomach.
,
113
(
2
), pp.
139
155
. 10.1115/1.2929069
8.
Arnone
,
A.
,
1994
, “
Viscous Analysis of Three–Dimensional Rotor Flow Using a Multigrid Method
,”
ASME J. Turbomach.
,
116
(
3
), pp.
435
445
. 10.1115/1.2929430
9.
Giovannini
,
M.
,
Marconcini
,
M.
,
Arnone
,
A.
, and
Dominguez
,
A.
,
2015
, “
A Hybrid Parallelization Strategy of a CFD Code for Turbomachinery Applications
,”
11th European Turbomachinery Conference
, Paper No. ETC2015-188,
Madrid
.
10.
Jameson
,
A.
,
Schmidt
,
W.
, and
Turkel
,
E.
,
1981
, “
Numerical Solutions of the Euler Equations by Finite Volume Methods Using Runge-Kutta Time-Stepping Schemes
,” AIAA Paper No. 81–1259.
11.
Swanson
,
R. C.
, and
Turkel
,
E.
,
1992
, “
On Central-Difference and Upwind Schemes
,”
J. Comput. Phys.
,
101
(
2
), pp.
292
306
. 10.1016/0021-9991(92)90007-L
12.
Roe
,
P. L.
, and
Baines
,
M. J.
,
1981
, “
Algorithms for Advection and Shock Problems
,”
Proceedings of the Fourth GAMM Conference on Numerical Methods in Fluid Mechanics, Notes on Numerical Fluid Mechanics, 5
,
Paris, France
,
Oct. 7–9
, p.
281
.
13.
Arora
,
M.
, and
Roe
,
P. L.
,
1997
, “
A Well-Behaved TVD Limiter for High-Resolution Calculations of Unsteady Flow
,”
J. Comput. Phys.
,
132
(
1
), pp.
3
11
. 10.1006/jcph.1996.5514
14.
Wilcox
,
D. C.
,
1998
,
Turbulence Modeling for CFD
, 2nd ed.,
DCW Industries Inc.
,
La Cañada, CA
.
15.
Boncinelli
,
P.
,
Rubechini
,
F.
,
Arnone
,
A.
,
Cecconi
,
M.
, and
Cortese
,
C.
,
2004
, “
Real Gas Effects in Turbomachinery Flows: A CFD Model for Fast Computations
,”
ASME J. Turbomach.
,
126
(
2
), pp.
268
276
. 10.1115/1.1738121
16.
Giles
,
M. B.
,
1988
,
Non–Reflecting Boundary Conditions for the Euler Equations
. Tech. rep., MIT Dept. of Aero. and Astro., CFDL Report 88-1.
17.
Giles
,
M. B.
,
1988
,
UNSFLO: A Numerical Method for Unsteady Inviscid Flow in Turbomachinery
. Tech. rep., MIT Dept. of Aero. and Astro., GTL 195.
18.
Saxer
,
A. P.
, and
Giles
,
M. B.
,
1993
, “
Quasi-Three-Dimensional Nonreflecting Boundary Conditions for Euler Equations Calculations
,”
J. Propul. Power
,
9
(
2
), pp.
263
271
. 10.2514/3.23618
19.
Cozzi
,
L.
,
2018
, “
Advanced CFD Modelling of Multi-Stage Axial Compressors
,”
Ph.D. thesis
,
Firenze
.
20.
Cozzi
,
L.
,
Rubechini
,
F.
,
Marconcini
,
M.
,
Arnone
,
A.
,
Astrua
,
P.
,
Schneider
,
A.
, and
Silingardi
,
A.
,
2017
, “
Facing the Challenges in CFD Modelling of Multistage Axial Compressors
,”
Proceedings of ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition
,
Charlotte, NC
,
June 26–30
, Paper No. GT2017-63240, V02BT41A007, pp.
1
11
.
21.
Gallimore
,
S. J.
,
1986
, “
Spanwise Mixing in Multistage Axial Flow Compressors: Part II—Throughflow Calculations Including Mixing
,”
ASME J. Turbomach.
,
108
(
1
), pp.
10
16
. 10.1115/1.3262009
You do not currently have access to this content.