INDUSTRIAL ENGINEERING IN DEPTH INVESTIGATIONS OF …€¦ · 16/04/2017 · ENGINEERING...
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DIEF DEPARTMENT OF INDUSTRIAL ENGINEERING DIEF DEPARTMENT OF INDUSTRIAL ENGINEERING A. PICCHI, A. ANDREINI, L. MAZZEI, R. BECCHI, B. F ACCHINI March 8th 2017 IN-DEPTH INVESTIGATIONS OF EFFUSION COOLED AERO-ENGINE COMBUSTORS ALESSIO PICCHI Department of Industrial Engineering – DIEF University of Florence - Italy
Transcript of INDUSTRIAL ENGINEERING IN DEPTH INVESTIGATIONS OF …€¦ · 16/04/2017 · ENGINEERING...
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
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DIEF DEPARTMENT OF
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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Nusselt number measurements – effect of effusion
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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
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Adiabatic effectiveness
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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
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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
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INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS
Simulation of swirling flows o Ansys CFX
– RANS reference simulation
– SAS
JGTP_138_05_051504
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RANS three sector
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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
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INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS
Effusion cooling modelling o Several models are available in the open literature
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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)
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INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS
SAFE methodology results
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Nu / Nu0
SAFE EXP SAFE EXP
Adiabatic effectiveness Nusselt number
GT2016-56603
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INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS 19
Effusion cooling modelling strategies GT2016-56603
4
1
3
2
SAS (mean) SAS (instantaneous)
1 2 3 4
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INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS
Conclusions
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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
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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
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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
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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
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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
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TLC
MAIN TLC
Black Paint Inconel
PVC
3D fem procedure for data post processing
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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
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INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS
Effusion cooling modelling
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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
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INTRODUCTION EXPERIMENTS NUMERICAL MODELLING CONCLUSIONS
Effusion cooling modelling strategies Heat transfer - spanwise average
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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)
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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
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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
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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
