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Publié par | Thesee |
Nombre de lectures | 39 |
Langue | English |
Poids de l'ouvrage | 11 Mo |
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ÉCOLE CENTRALE DE LYON
N°ordre: 201012 Année 2010
THÈSE
en vue d’obtenir le titre de
DOCTEUR DE L’ÉCOLE CENTRALE DE LYON
ÉCOLE DOCTORALE M.É.G.A.
MÉCANIQUE, ÉNÉRGETIQUE, GÉNIE CIVILE ET ACOUSTIQUE
Par
Ankit SACHDEVA
STUDY AD COTROL OF THREE DIMESIOAL FLOW
SEPARATIOS I A HIGH PRESSURE COMPRESSOR STATOR
BLADE ROW BY BOUDARY LAYER ASPIRATIO
SOUTENUE LE 21 JUIN 2010 À L’ÉCOLE CENTRALE DE LYON
JURY
L. JACQUIN Directeur du DAFE, ONERA, Meudon Président
G.GEROLYMOS Professeur, UPMC, Paris Rapporteur
G.BOIS Professeur, ENSAM, Villeneuve d’Ascq Rapporteur
F. LEBOEUF Professeur, ECLyon, Ecully Directeur de thèse
T. OBRECHT Ingénieur, SNECMA, Villaroche Examinateur
L. CASTILLON Ingénieur, ONERA, Meudon Examinateur
ACKOWLEDGEMETS
I express my sincere gratitude to the director of my thesis Professor Francis LEBOEUF for his
kind support and continued guidance throughout the work of this thesis. An enlightening
teacher and a very patient person, he has been like a guiding lighthouse in all the times.
I thank M. Armel TOUYERAS, M. Thierry OBRECHT and M. Michel DUMAS for their
support and supervision over the entire duration of this work. Their experience and
management skills have been crucial to meet the objectives of this work.
I extend my gratitude for our external partners such as ONERA, EPFL and LMFA for their
contributions in making this thesis and project meet its objectives. I specially thank Lionel
CASTILLON of ONERA for his support in advanced numerical modelling and computations.
I thank M. Elia COLOMBO and M. François BARIO for their discussions involving their
work on experimental setup and measurements.
I thank the secretary of our department at Snecma Mrs. Marie Claude CHEVALIER for her
tireless contribution in managing the official work of this thesis such as travelling and lodging
on various occasions.
Last but not the least; I thank all the colleagues of the high pressure compressor team at
Snecma for their support and company during my stay at Snecma.
OMECLATURE
BLADE GEOMETRY NOTATIONS
β Blade metal angle
c Blade chord
z,H Blade span
s Blade pitch
AR Blade aspect ratio (span/chord)
σ Blade solidity (chord/pitch)
λ Blade stagger angle
ζ Blade camber angle
BOUNDARY LAYER NOTATIONS
δ Boundary layer thickness
*δ Displacement thickness
θ Momentum thickness
FLOW TOPOLOGY NOTATIONS
N Node
F Focus, Spiral node
S Saddle point
ℓ Separation line
τ Friction vector
NONDIMENSIONAL NOTATIONS
DF Leiblein’s Diffusion factor
DP Diffusion parameter
Ma Mach number
SI Stall Indicator
Re Reynolds number
GREEK SYMBOLS
ρ Flow density
L Vorticity
∇ Divergence operator
Ψ Zweiffel loading coefficient
Oβ Boundary layer turning due to rotating wall
ϖ Total pressure loss coefficient
η Efficiency
α Flow angle
δ Flow deviation
γ Ratio of specific heats
ε Epsilon (rate of dissipation of turbulent kinetic energy)
Coefficient of dynamic viscosityυ Coefficient of kinematic viscosity
ABBREVIATIONS
2D Two dimensional
3D Three dimensional
BLS Boundary layer suction
CAD Computer Aided Design
CFD Computational Fluid Dynamics
DES Detached Eddy Simulations
grad gradient
HPC High Pressure Compressor
LE Leading Edge
LES Large Eddy Simulations
OT Off take (device to bleed air from blade passage)
PS Pressure surface
P Static Pressure S
P Total pressure T
PVD Prescribed velocity distribution
RANS Reynolds averaged Navier Stokes
rot rotational operator
SS Suction surface
TE Trailing edge
VG Vortex generator
MISCELLANEOUS
u ,V Freestream / inviscid velocity o
Cq Aspiration/suction coefficient
+y Wall function
R Universal gas constant
K Turbulent kinetic energy
L Characteristic length (m)
E(K) Spectrum of turbulence
SUBSCRIPTS
1,2 Upstream, Downstream
abs absolute
0 inviscid local condition
x axial direction
θ circumferential direction
r radial direction
t turbulentABSTRACT
The performance of the compression system of a gas turbine engine is limited for a large part
by the threedimensional separations occurring in the high pressure compressors. The effects
of flow separation are more important in the endwall regions where the fluid tends to
decelerate and accumulate in regions of low momentum. The theme of this research work is to
implement boundary layer aspiration to control flow separations in high pressure
compressors. This is achieved by implementing aspiration devices on the endwall and blade
profile to judiciously remove low energy fluid in the boundary layers that enables higher
pressure rise per stage. This thesis is a joint scientific work associating Ecole Centrale de
Lyon (ECL), Ecole Polytechnique Federale de Lausanne (EPFL) and ONERA. The European
Commission under the frame of the programme NEWAC and the enterprise SNECMA has
financed this research work.
The test case is a stator blade row designed to operate with transonic inlet conditions. Three
dimensional steady state RANS computational studies are done to define the operating range
of the cascade with emphasis on the study of bladetoblade flow topologies to understand the
formation and progression of the corner separation on the hub wall with increasing inlet
incidences. Boundary layer aspiration is implemented on the hub wall to control the three
dimensional flow separations to improve the pressure rise and the operating range. The
aspiration strategy is sensitive to the aspirated massflow; lower aspirated flow rate results in
complex flow separation topologies with deteriorated performance, while higher aspirated
flow rate is found to suppress the corner separation and improve the diffusion capability
except at the highest incidence point. The analysis of flow topologies shows the recirculation
of flow between the aspiration cavity and the blade passage; a highly complex three
dimensional flow phenomena that influences the blade performance. The study of flow
topologies is instrumental in developing rationales for the implementation of flow control.
This aspiration strategy is studied experimentally at EPFL where aspiration has been
implemented on the hub wall. A new set of numerical studies done with inlet conditions
measured from the test bench associated with rational hypothesis concludes this task with
reasonable agreement between the experiments and numerical simulation. In particular, the
hub corner separation is predicted well by CFD.
Computational studies are done to implement aspiration on the blade profile to improve the
diffusion capability of the blades; various sensitivity parameters such as aspiration slot
locations, aspirated flow rate are studied and a configuration is finalised for the experiments
to be followed. Some studies are performed with smaller and multiple slots on the blade
profile. The results show the merit of applying localised flow control on the critical points
associated with flow separation demonstrating the scope to achieve higher levels of
performance with lower aspirated flow rates.
Keywords: High pressure compressors, three dimensional flow separations, boundary layer
aspiration, flow topologies. RÉSUMÉ
La performance du système de compression des turbomachines est limitée en grande partie
par les décollements tridimensionnels; ils sont plus importants au niveau des parois internes
où le fluide a tendance à décélérer dans les zones de faible impulsion. Ce travail de recherche
met en œuvre l'aspiration de la couche limite afin de maîtriser les décollements dans les
compresseurs. Ceci est obtenu par la mise en place de dispositifs d'aspiration sur le moyeu et
le profil de l’aube afin de prélever judicieusement le fluide à faible énergie dans les couches
limites et ainsi augmenter le taux de compression par étage. Cette thèse est issue de travaux de
recherche réalisés conjointement avec l'Ecole Centrale de Lyon (ECL), l’Ecole Polytechnique
Fédérale de Lausanne (EPFL) et l'ONERA. Ces travaux ont été financés par la Commission
Européenne dans le cadre du programme NEWAC et l’entreprise SNECMA.
Le cas test est une grille annulaire de redresseur conçu pour fonctionner avec des conditions
d'entrée transsoniques. Des calculs stationnaires tridimensionnels RANS sont réalisés afin de
définir la plage de fonctionnement de la grille en mettant l'accent su