bianchinicosimo phd official 13 april 2011

8/7/2019 BianchiniCosimo Phd Official 13 April 2011

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University of FlorenceDepartment of Energy Engineering

Assessment of boundaryconditions for heat transfer and

aeroacoustic analysis

Cosimo Bianchini

HTC groupEnergy Engineering Department

Via di S.Marta 3, 50139 Firenze

[email protected]


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2Cosimo Bianchini PhD thesis dissertation 13/04/2011

DNS near wall LES far field LES Advanced RANS RANS

Effusion cooling Effusion acoustic Impingement jet

Outline Introduction

Conjugate generic grid interface

Effusion cooling overall effectiveness

Mapped inlet condition

Heat transfer of axisymmetric impingement jet

Navier-Stokes characteristic boundary conditions

Acoustic response of perforated combustor liners

Conclusions


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Motivation

Dome coolingImpingement arrays

Liner coolingEffusion systems

Stricter requirements for pollutant emission

Lean Partially Premixed technology

Reduced amount of air for cooling purposes

Improve cooling efficiency

Decreased stability of flames working close to the lean limit

Employ systems to damp acoustic fluctuations in combustion chamber

Present-day aeroengines combustion chambers cooling is obtained by:

Effusion for the liner

Impingement in the dome

Detailed analysis of aero-thermo-dynamics of cooling systems

Reliable evaluation of cooling performance

Interaction with the main flow

Effects on combustion


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Motivation

Accurate numerical predictions to reliably help designers needs to

overcome known failures of standard CFD analysis

Unsteady effects

Steady effects generated by large scale phenomena

Thermal interaction with surrounding solids

at a computationally affordable level

implementing in the context of open-source CFD

OpenFOAM

methods for:

Conjugate Heat Transfer analysis

Large Eddy Simulation

Increased complexity require adequate boundary treatment

Energy balance on the interface needs to be respected

Grid scale turbulence needs to be specified

DNS

Wall resolved

LES

Far field

LES

AdvancedRANS

RANS


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Objectives

The aim of the thesis is to

implement, validate and assess state of the art boundary conditions for the studyof heat transfer and aeroacustic phenomena connected with combustor cooling

Technological problems faced

Estimate the combined effect of film protection and heat sink in effusion cooling

devicesEvaluate the cooling capabilities of impingement jets

Assess the potential of perforated liners as acoustic dampers for the stabilizationof lean flames

Computational aspects

Conjugate interface boundary condition to couple fluid and solid domain

Turbulent inlet generation to increase confidence on obtainable results

Non-reflecting inflow and outflow boundaries with acoustic forcing


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Conjugate interface

Energy equation solved in terms of temperature (static or total)

Fluid: convective-diffusive equationSolid: Fourier equation

Coupled boundary guaranteesContinuity of temperatureContinuity of heat flux: temperature gradient

Different mesh requirements of fluid and solid sideNo boundary layer in solid domainStrictly apply only to Low-Reynolds computations

Non conformal interface treatment

same matrix for solidand fluid domain

fwsw TT ,, =

fw

f

sw

sn

Tk

n

Tk

,,

=


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Multiple implicit coupling - ghost cell mechanism

Contribution of ghost cell calculated via cell-to-cell addressing andweighting factors i

Weighting factors based on face overlapping areasAlgorithm for overlapping area based on surface integral of the product ofthe winding number of the two polygonsApplies to every non self-intersecting polygon, positively oriented: alltypes of meshes can be used (tetra,hexa,poly,etc..)

( ) ,1f p p p i n ii

w w = +

,i o i fpA A =

,n i n iC C=

Domain 1

Domain 2 p

n1 n2

Non conformal interface

Generic grid interface


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Effusion cooling conjugate analysis

Conventional (circular hole) and shaped (circular imprint) holes

Same porosity, same slanted angle:17

High temperature rig (Poiters): heat shield, 17-12 rows

3.5 millions cells hybrid mesh for 8 rows

Steady-state RANS analysis: Two-Layer (TL) and anisotropicTwo-Layer (ATL) turbulence models

ConventionalShaped


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Turbulent inlet generation

Perfect turbulent inlet generation should:be compatible with the Navier-Stokes equations

look like turbulence

allow easy specification of turbulent integralproperties

be easy to implement and to adjust to new inletconditions

be cost efficient and computationally cheap

Internal mapping

Identify an internal portion of the domain to applyrecycling methods

Feedback

Is guaranteed by scaling the mapped field to

satisfy specified surface (or mass flow)integral values

Mapped fluctuation: same procedure apply to besuperposed on desired profiles


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Axisymmetric Impingement Jet

Ercoftac database: Re= 23000, H/D=2

Detailed experimental data

mean flow field and fluctuations [Cooper et al.,1993]

Nusselt number [Baughn and Shimizu,1989]

5.2 millions cells, 84 blocks hexahedral mesh

Incompressible Large Eddy simulation

Additional equation for temperature

Fully developed inlet condition

Mapped and Mapped fluctuation (from pipe simulation)

Convective condition on outlet and top boundaries

One equation sgs model: transport equation for turbulent kinetic energy

0=

+

n

UC

t

U

Mapped Mappedfluctuation


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Mean velocity

Impinging zone

Wall jet zone

R/D = 0 R/D = 0.5

R/D = 1 R/D = 2 R/D = 3

DNS ll LES f fi ld LES Ad d RANS RANS


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Effective fluctuations

Radial fluctuations

Axial fluctuations

''

rrUU

R/D = 0.5 R/D = 1 R/D = 2 R/D = 3

''

zzUU

R/D = 3R/D = 2.5R/D = 1R/D = 0.5

f DNS ll LES f fi ld LES Ad d RANS RANS


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Constant and uniform heat flux: mean Nusselt number

Controversy on stagnation point dip and secondary peak

Secondary peak due to periodical impingement of broken ring vortex

Too low axial fluctuations might have lowered Nu for r/D > 1.5

U i it f Fl DNS ll LES f fi ld LES Ad d RANS RANS


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Non reflecting boundaries

Navier Stokes Characteristic Boundary Conditions (NSCBC)

Characteristic wave analysis on the boundary

NSE are rewritten on the boundary in terms of waveamplitude variations

Entering waves: imposed by means of LinearRelaxation Method exploiting Local One Dimensional

Inviscid (LODI) hypothesisOutgoing waves: extrapolation from internal solution

NSE are integrated on the boundary to obtain primitive variablestime advanced

Introduction of transverse and diffusive terms

The reflectivity of the boundary is driven byAcoustic forcing is introduced with variable target value

= c,,,n

p,

n

ufL

)( TL =

L

)cos( += tAT

U i it f Fl DNS near all LES far field LES Ad anced RANS RANS


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Acoustic responce of perforated platesBellucci test

Experimental [Bellucci, 2004],LES and other numerical data [Mendez,2009] available

Pulsed pressure outflow and fully reflecting inlet with NSCBC

Wall Adaptive Local Eddy (WALE) viscosity model

Multiblock exahedral mesh of 5105 cells

Estimate reflection coefficient of perforated plate with bias flow

Multimicrophone (4 stations) post processing technique

Reconstruction of progressive and regressive wave by means of a leastsquare fitting

+

+

=R

Flow conditions

U 5 m/s

u 0.115 m/s

T 293.15 K

pref 100000 Pa

p 5 Pa

U i it f Fl DNS near wall LES far field LES Advanced RANS RANS


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Acoustic responce of perforated platesBellucci test

University of Florence DNS near wall LES far field LES Advanced RANS RANS


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Acoustic responce of perforated platesKIAI test

Same set up, different geometry and much higher bias flow Mab=0.1

Multifrequency excitation

Effect of stagger studied with different cyclic boundary arrangement at 1000 Hz

=i

ii

T tAp )cos(

in linestaggered rhomboidal staggered rectangular



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KIAI test Flow field analysis

Instantaneous axial velocity show typical turbulentbehaviour

No vena contracta due to the high L/D

Modal analysis performed with Proper Orthogonal

Decomposition techniqueEquivalent but symmetric modes found at 3 and 5

Corresponding velocity modes showed that:

Mode 2: vortex rings aligned with hole axis

Mode 4: vortex rings misaligned with hole

axis

POD pressure modes



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Conclusions

Several boundary conditions were implemented in an open-source CFD code

A conjugate interface with implicit non-conformal coupling

An internal mapping turbulent inlet generator

A non and partially reflecting inflow and outflow conditions

The capability to improve accuracy of prediction was tested under conditions relevantfor combustor liners cooling system design

An effusion cooling device at engine like condition

An axisymmetric impingement jet with heat transfer

The acoustic response of perforated liners with bias flow

The implemented conditions showed results aligned with state of the art computations

Further work should be addressed towards improving efficiency (conjugate interface),

robustness (Mapped condition) and stability (NSCBC)



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Publications Bianchini, Mangani, Andreini, Facchini, Development and validation of a C++ object oriented cfd code for heat

transfer analysis", 2007, ASME PAPER AJ-1266, Thermal Engineering and Summer Heat Transfer Conference, Vancouver

Bianchini, Da Soghe, Facchini, Innocenti, Micio, Bozzi, Traverso, Development of numerical tools for stator-rotorcavities calculation in heavy-duty gas turbines", 2008, ASME PAPER GT2008-51266, Asme Turbo Expo, Berlin

Bianchini, Facchini, Mangani, Conjugate heat transfer analysis of an internally cooled turbine blades with anobject oriented cfd code", 2009, European Turbomachinery Congress, Graz

Andreini, Bianchini, Ceccherini, Facchini, Mangani, Cinque, Colantuoni, Investigation of circular and shapedeffusion cooling arrays for combustor liner application Part II: Numerical analysis", 2009, ASME PAPERGT2009-60038, Asme Turbo Expo, Orlando

Boust, Lalizel, Bianchini, Facchini, Cinque, Colantuoni, Dual investigations on the improvement of effusion cooling

by shaped holes", 2009, 7th World Conference on Experimental Heat transfer Fluid mechanics Thermodynamics, Krakow Bianchini, Simonetti, Zecchi, Numerical and experimental investigation of turning flow effects on innovative pin fin

arrangements for trailing edge cooling configurations, 2010, ASME PAPER GT2010-23536, Asme Turbo Expo,Glasgow to appear on Journal of Turbomachinery

Bianchini, Mangani, Maritano, Heat transfer performance of fan-shaped film cooling holes. Part II Numericalanalysis, 2010, ASME PAPER GT2010-22809, Asme Turbo Expo, Glasgow

Bianchini, Bonanni, Carcasci, Facchini, Tarchi, Experimental survey on heat transfer in an internal channel of atrailing edge cooling system, 2010, 65 ATI conference

Bianchini, Andreini, Facchini, Numerical analysis of the heat transfer in a trailing edge cooling duct in stationaryand rotating conditions, 2011,9th European Turbomachinery Congress, Istanbul

Andreini, Bianchini, Armellini, Casarsa, Flow field analysis of a trailing edge internal cooling channel, 2011, ASMEPAPER GT2011-45724, Asme Turbo Expo, Vancouver, Accepted for publication

Simonetti, Andreini, Bianchini, Assessment of numerical tools for the evaluation of the acoustic impedance ofmulti-perforated plates, 2011, ASME PAPER GT2011-46303, Asme Turbo Expo, Vancouver, Accepted for publication

University of Florence


21/21


Assessment of boundaryconditions for heat transfer and

aeroacoustic analysis

Cosimo Bianchini

HTC groupEnergy Engineering Department

Via di S.Marta 3, 50139 Firenze

[email protected]

bianchinicosimo phd official 13 april 2011

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