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DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
A. PICCHI, A. ANDREINI, L. MAZZEI, R. BECCHI, B. FACCHINI March 8th 2017
IN-DEPTH INVESTIGATIONS OF EFFUSION COOLED AERO-ENGINE COMBUSTORS
ALESSIO PICCHI
Department of Industrial Engineering – DIEF University of Florence - Italy
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS
Background and motivations
• Drastic limitations to emissions of civil aero-engines
– (2020 ACARE goals and ACARE Flightpath 2050)
• NOx: -80%, CO2: -50%, reduction of soot, uHC, SOx, noise
Effusion cooling concept
• Implementation of lean burn combustion for high OPR future aero-engine
– Control of local stoichiometric conditions
– Limitation of temperature peaks
– NOx abatement
• Implications
– More air dedicated to combustion process
– Coolant has to be reduced by 50%
→ More effective cooling schemes
→ More accurate estimation of heat loads
2
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS
Lean burn concepts o Direct injection of fuel spray into combustion air to have an overall lean
mixture – Efficient and rapid fuel atomization required
– Flame stabilization by highly swirling flow with relevant hot gas recirculation
o GE AVIO technology – PERM – Partially evaporated and rapid mixing
3
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS
Effusion cooling
o Huge number of small inclined holes – Diameter below 0.6 mm
– Angle below 30°
– High porosity, reduced weight
– Heat transfer mechanisms involved - contributions • Film cooling o hot surface 30%
– Improved by starter slot – Depleted by interaction with unsteady swirling gas flow
• Heat removed by forced convection inside holes 40%
• Improved cold side convective cooling 30%
Characteristics
4
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS
Main issues related to combustor thermal design
Swirling flow-liner interaction
– Limited knowledge
– Strong impact on film cooling behaviour and heat transfer coefficient distributions
– Limited accuracy of correlative approaches
Effusion cooling
– Film effectiveness
– Impact on heat transfer coefficient on both hot and cold side
– Heat sink effect
GT2014-26764
5
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS
Outline
IN-DEPTH INVESTIGATIONS OF EFFUSION COOLED AERO-
ENGINE COMBUSTORS
Experimental investigations – PIV flow field measurements highlighting
the impact of effusion injection
– Heat transfer coefficient measurements
– Adiabatic effectiveness results
Numerical modelling – Scale Resolving Simulations of
combustor flow field – Nusselt number evaluation – Effusion cooling modelling strategies
Integrated experimental and numerical investigations required
6
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS
Track records – LEMCOTEC project
Low Emissions Core-Engine Technologies
Organized in four Sub-Projects
SP3: Lean Combustion for ultra-high OPR engines
Cooling system
7
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS
Outline
IN-DEPTH INVESTIGATION OF EFFUSION COOLED AERO-
ENGINE COMBUSTORS
Experimental investigations – PIV flow field measurements highlighting
the impact of effusion injection
– Heat transfer coefficient measurements
– Adiabatic effectiveness results
Numerical modelling – Scale Resolving Simulations of
combustor flow field – Nusselt number evaluation – Effusion cooling modelling strategies
Integrated experimental and numerical investigations required
8
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS
Thermal effectiveness investigations
o Open Loop suction type wind tunnel: three separate flows (mainstream, slot and effusion)
o Test Section: Three swirlers and a complete cooling scheme (effusion+slot)
Cold Sector Test Rig
9
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
DIEF DEPARTMENT OF
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ENGINEERING
INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS 10
Optical measurements technique
Particle Image Velocimetry (PIV)
– Displacement of particles seeded to the flow
– 2 measurement planes
TLC steady state – Temperature surface
measurements imposing a wall heat flux
Pressure sensitive paint (PSP) technique for film effectiveness
– Heat and mass transfer analogy based on feeding the cooling lines with foreign gas
– Intensity emitted by the paint is function of the wall oxygen concentration
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
DIEF DEPARTMENT OF
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ENGINEERING
INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS 11
Flow field: median and center planes
2.4
2.0
1.6
1.2
0.8
0.4
x/D
0 0.4 0.8 1.2 1.6 -0.4 -0.8 -1.2 -1.6
y/D
U/Umax
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
o High velocity jet at the injector exit
o Generation of an unique flow structure by the jets interaction
o Toroidal recirculation due to vortex breakdown
o Jet impinges on liner at x/D=0.6
o Strong axial accelerations near the wall
DIEF DEPARTMENT OF
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DIEF DEPARTMENT OF
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INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS
Nusselt number measurements – effect of effusion
12
Nu / Nu0 No coolant
0.2 0 0.4 0.6 0.8 -0.6 -0.8 -0.4 -0.2
y/D
ΔP/Peff = 3%
0.2 0 0.4 0.6 0.8 -0.6 -0.8 -0.4 -0.2
y/D
o Elliptic area where HTC reaches the peak values and low HTC values in the corner RCZ
o Elliptic area remains still visible introducing the effusion flow
o The coolant injection leads to a significant increase of HTC
Swirling flow-liner interaction in presence of slot and effusion cooling
Nu/Nu0
o The coolant injection leads to a significant increase of HTC
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS
Adiabatic effectiveness
13
o Strong effect of swirling flow on film covering
o Slot protection early deteriorated
o Coolant washed by swirling flow in the central region
Swirling flow-liner interaction in presence of slot and effusion cooling
ηaw
JGTP_138_03_031506
No slot Slot + Effusion
ηaw
Effusion flat plate
Effusion with swirler
0 2 4 6 8 10 12 14 16 180.0
0.1
0.2
0.3
0.4
0.5
0.6
ad
x/Sx
P/Peff
=3%
G1 VR 2.0
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS
Outline
IN-DEPTH INVESTIGATION OF EFFUSION COOLED AERO-
ENGINE COMBUSTORS
Experimental investigations – PIV flow field measurements highlighting
the impact of effusion injection
– Heat transfer coefficient measurements
– Adiabatic effectiveness results
Numerical modelling – Scale Resolving Simulations of
combustor flow field – Nusselt number evaluation – Effusion cooling modelling strategies
Integrated experimental and numerical investigations required
14
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS
Simulation of swirling flows o Ansys CFX
– RANS reference simulation
– SAS
JGTP_138_05_051504
15
RANS three sector
DIEF DEPARTMENT OF
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ENGINEERING
DIEF DEPARTMENT OF
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ENGINEERING
INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS 16
CFD investigation of effusion cooled combustors
• Complexity of swirling flow-liner cooling interaction
Two-way coupling with film cooling
Poor representativeness of correlative approaches (derived from flat plates)
Good agreement achieved with CFD
Especially with «advanced» turbulence models (SAS, DES, LES…)
• Numerical issues related to implementation of effusion cooling
Appropriate turbulence modelling required
Intrinsic limits of RANS approach
Computational effort
(At least) 100 000 mesh element per hole
2000-5000 holes per combustor sector
DIEF DEPARTMENT OF
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ENGINEERING
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS
Effusion cooling modelling o Several models are available in the open literature
17
SAFE methodology: Source Based Effusion Model
• Mass flow rate calculated at run time starting from local flow conditions Momentum flux with nominal inclination
angle
• Correlative approach for the calculation of CD and HTC
• Evolution of the model proposed by Voigt et al. 2012 Point Source feature
• Hole replaced by means of sink/source for mass, heat and momentum : Applied locally with Source Points
(native feature of Ansys CFX)
DIEF DEPARTMENT OF
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ENGINEERING
DIEF DEPARTMENT OF
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ENGINEERING
INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS
SAFE methodology results
18
Nu / Nu0
SAFE EXP SAFE EXP
Adiabatic effectiveness Nusselt number
GT2016-56603
DIEF DEPARTMENT OF
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ENGINEERING
DIEF DEPARTMENT OF
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ENGINEERING
INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS 19
Effusion cooling modelling strategies GT2016-56603
4
1
3
2
SAS (mean) SAS (instantaneous)
1 2 3 4
DIEF DEPARTMENT OF
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ENGINEERING
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS
Conclusions
20
o Interaction between swirling flow and liner wall – Experiments has shown the paramount role in the determination of the convective heat
loads
– Reliability of hybrid RANS/LES approaches (especially SAS)
o Effusion behavior – Film protection deeply influenced by the unsteady swirling flow
– Starter film cooling acts its protection only in the first part of the liner
– Encouraging agreement between time-averaged quantities from EXP and the results of the proposed source point model
o Deeper insight into the unsteady behavior increasing the representativeness of the test case
….and Future perspectives
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
A. PICCHI, A. ANDREINI, L. MAZZEI, R. BECCHI, B. FACCHINI March 8th 2017
IN-DEPTH INVESTIGATIONS OF EFFUSION COOLED AERO-ENGINE COMBUSTORS
EXPERIMENTAL ACTIVITIES:
ALESSIO PICCHI*
RICCARDO BECCHI
NUMERICAL SIMULATION:
ANTONIO ANDREINI*
LORENZO MAZZEI
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS
Flowfield measurements o Dantec Dynamic 2D PIV system
– 120mJ New Wave Nd:YAG pulsed laser 532nm
– FlowSense 2Mpixel camera
– Laskin nozzle
Steady PIV
22
8 camera/laser positions 16 camera/laser positions
Measurement planes
Data acquisition
2 measurement planes
480 image pairs
Time delay 10-40 μs
Laser sheet 1mm
Data post process
Adaptive grid iterative method
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
DIEF DEPARTMENT OF
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ENGINEERING
INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS
HTC measurements o Steady state technique with isothermal flows conditions
o Surface heat flux: Inconel heating foil 25.4μm
– Two copper bus bars on lateral side
o Wall temperature: TLC wide band 30-50°C
TLC technique
23
TLC
MAIN TLC
Black Paint Inconel
PVC
3D fem procedure for data post processing
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS
Adiabatic effectiveness measurement
o Painting based on an organic substance with oxygen sensitive molecules Luminescence behaviour o Heat-Mass transfer analogy by the assumption of LeT=1
o Oxygen quenching: intensity from the paint is a function of the partial pressure of oxygen
o Tracer gas without free oxygen is used as coolant in a film cooling system
→ 2D maps of adiabatic effectiveness
PSP technique
24/19
𝜂𝑎𝑤 =𝑇𝑚𝑎𝑖𝑛 − 𝑇𝑎𝑤𝑇𝑚𝑎𝑖𝑛 − 𝑇𝑐𝑜𝑜𝑙
≡𝐶𝑚𝑎𝑖𝑛 − 𝐶𝑤
𝐶𝑚𝑎𝑖𝑛= 1 −
𝑃𝑂2 ;𝑓𝑔/𝑃𝑂2 ;𝑟
𝑃𝑂2;𝑎𝑖𝑟/𝑃𝑂2 ;𝑟
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
DIEF DEPARTMENT OF
INDUSTRIAL
ENGINEERING
INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS
Effusion cooling modelling
25
Uniform injection (AHM)
[1] Mendez and Nicoud 2008
Discrete hole
Model
• The perforation is replaced by an homogeneous boundary condition Coarse grid in the near wall region
DIEF DEPARTMENT OF
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DIEF DEPARTMENT OF
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ENGINEERING
INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS
Effusion cooling modelling strategies Heat transfer - spanwise average
26
EXP
0.2
0.4
0.6
0.8
1
1.2
1.4
1.8
1.6
2
2.2
x/D
0.2 0 0.4 0.6 0.8 -0.6 -0.8 -0.4 -0.2
y/D
Nu / Nu0
0.2 0 0.4 0.6 0.8 -0.6 -0.8 -0.4 -0.2
y/D 0.2 0 0.4 0.6 0.8 -0.6 -0.8 -0.4 -0.2
y/D
Exp uncertainty ≈8%
AHM (time avg) SAFE (time avg)
DIEF DEPARTMENT OF
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DIEF DEPARTMENT OF
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ENGINEERING
INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS
Simulation Quality
o Pope’s criterion – Target: at least 80% of tke resolved
– SAS:
• Criterion satisfied in most of the domain
• Small impact of mesh refinement
– DES:
• Switches to RANS near wall
• Significant mesh refinement required
• Celyk’s criterion
Target: comparison of scales
Nearly equivalent for SAS and DES
Fully satisfied for the refined mesh
DIEF DEPARTMENT OF
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Antonio Andreini 28
SAFE methodology - Validation
• Definitions of best practices for meshing – Sensitivity to mesh refinement:
• mesh size equal to 0.5D – Sensitivity to blowing ratio:
• Better performance in penetration regime
• Comparison with experimental results from KIAI project
Discrete hole
Modelled hole
DIEF DEPARTMENT OF
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Antonio Andreini 29
SAFE methodology - Application TECC
• TECC-AE tubular combustor (Journal Eng GT Power, 2013) – Reactive test rig for experimental tests on injection systems – Impingement for dome cooling – Effusion for liner cooling
Flow field
Flow split Temperature distribution