MUSCLES Modelling of Un s teady Combustion in Low Emission Systems

Mid Term Meeting, Sept. 21st-22nd, 2004, Karlsruhe Presentation by: F.Pittaluga - UNIGE-DIMSET

Dept. of Fluid Machinery, Energy Systems and Transportation - University of Genoa, Italy

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MUSCLES

Modelling of Unsteady Combustion in Low Emission Systems

G4RD-CT-2002-00644

R&T Project within the 5th Framework Program of the European Union



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Time-Dependent Numerical Simulations of the One-Phase as well as the Multi-Phase

Flow Fields within an LPP Aero-Engine System



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NastComb Code

CRFD (Computational Reactive Fluid Dynamics) code, extensively developed at DIMSET, and continuously improved and validated

Three-dimensional, turbulent, multi-phase, reactive flows

Ensemble-averaged, fully time-dependent (fast-transient tracking) numerical scheme

Main features: ALE method , TSDIA/MTS turbulence model, liquid-fuel spray simulation, fully detailed chemistry



4

NastComb: Spray Modeling

Stochastic technique Discrete particles methodCollision, break-up, evaporationTAB model

– Taylor Analogy Break-up– Liquid droplet deformation

yr

Cyr

Cr

u

C

Cy

l

ld

lk

l

g

b

F 232

2



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RTKH Model

Stability analysis→Dispersion equation→Fastest growing wavelength

Kelvin-Helmoltz instabilities

•Relative velocity

Rayleigh-Taylor instabilities

•Interface acceleration

aBtbu 1726.3

0Br

1but

2

RTCr

Only KH model with droplets stripping

Jet primary breakup

RT+KH competition

Secondary breakup



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A First TAB/RT-KH Comparison

Primary jet break-up in stagnant gas

Fuel c13h30

Nozzle diameter 0.2 mm

Fuel injection velocity 40 m/s

Air Temperature 300 K

Air pressure 2000 kPa

Jet Weber number 210

Grid Size 1*1*1 mm^3

Domain size 5 cm radial*15 cm axial

Simulation time 3.5 ms

No evaporation

No collision



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TAB Model - RTKH Model Compared

RTKH model

TAB model



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TAB Model•SMR= 43 micron

•Droplet N°= 6000

RTKH model•SMR= 25 micron

•Droplet N°= 20000



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Ultra Low NOx “LRPM” Technology

• Objective: to pursue NastComb calibration/validation in reactive conditions

• Ultra-lean, fully-premixed combustion process with liquid fuels

• Reduction of temperature levels (and gradients) to the advantage of Nox limitation

• High flame-stability characteristics

Combustion chamber

Premixer

Air inlet



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SCL/LRPM Test Rig

also: propane, gas-oil and jet-A

Distillate #2 Liquid fuel type

Fully verified in several test campaigns

10 - 15 ppmNOx level

max, pc-controlled

110 kWElectrical preheating power

nominal, sustainable up to 1.3 bar

1.15 barCombustor pressure

nominal, ultra-lean, controllable

0.42Equivalence ratio

max, from fuel injection 200 kWThermo-chemical power

max, pc-controlled 350 °CBurner-inlet air temperature

nominal, pc-controlled 500 kg/hAir flow rate



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Preheated Two-Phase Flow Simulation

Operative conditions adopted

Air flow rate 315.2 Nm3/h

Air inlet temperature 333 °C

Inlet pressure 1.10 * 105 Pa

Fuel Type Jet-A

Nozzle diameter 0.3 mm

Fuel flow rate 0.182 l/min

Fuel inlet temperature 100 °C

Equivalence ratio 0.40

Preheating power 85000 kW



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Numerical Mesh



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TAB/RT-KH Comparison

TAB model

RTKH model



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TAB/RT-KH Comparison

TAB model

RTKH model

After RT effect



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Reactive Predictions (LRPM Burner)



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Spray Models and Implementation

NastComb solver is now provided with the RTKH model as a new option for improved predictions (unreactive and reactive)

Taking advantage of the very recent experimental data referred to the enlarged-scale Avio LPP model-rig, a unique opportunity has become available in order to pursue detailed calibration and validation for both one-phase as well multi-phase pre-heated flows in real-application conditions .

With above validations, NastComb solver has attained a quite interesting, reliable, application potential



Time Dependent Prediction of the One-PhaseTime Dependent Prediction of the One-Phase Flow-Field Within an LPP Aero-Engine SystemFlow-Field Within an LPP Aero-Engine System

MUSCLES Mid-Term Meeting, September 21st-22nd, 2004 Karlsruhe



LPP System Computational ConditionsLPP System Computational Conditions

Computational GridComputational Grid

Grid type: Structured-MultiblockN° of total Blocks: from 203 to 451Geometry: Fully 3D°N° of total cells: from 994000 to 2450000

Boundary Conditions Boundary Conditions

Mass Flow : 0.4 kg/sStatic Temperature Inlet : 298 KStatic Pressure Outlet : 101680 Pa

Experimental Test RigExperimental Test Rig

Zmax = 750 mm - Xmax = 250 mm - Ymax = 250 mm



Computational Results and ValidationComputational Results and Validation

Z= +30 mmZ= +30 mm

Meridian PlaneMeridian PlaneMesh Size : 994 000Mesh Size : 994 000

Time Dependent Numerical ResultsTime Dependent Numerical Results

Traversing Z= +30 mmTraversing Z= +30 mmMesh Size : 2 450 000Mesh Size : 2 450 000

CaCa CrCr CtCt

Meridian Meridian PlanePlane

Meridian & Cross Meridian & Cross Section PlanesSection Planes

Mesh Size : 2 450 000Mesh Size : 2 450 000



Computational Computational PowerPower

LINUX CLUSTER “APOLLO”LINUX CLUSTER “APOLLO”

Cpu’s : 12 Athlon™ MP 2.0 GHz

Ram : Master 2 Gb DDR 266 Slaves 1 Gb DDR 266

Storage Capacity : 480 Gb

Network : 3COM ™ Gigabit



ANNEX 4ANNEX 4

Time Dependent Prediction of the Multi-PhaseTime Dependent Prediction of the Multi-Phase Flow-Field Within an LPP Aero-Engine SystemFlow-Field Within an LPP Aero-Engine System

MUSCLES Mid-Term Meeting, September 21st-22th, 2004 Karlsruhe



LPP System: Two Phase Flow Computational ConditionsLPP System: Two Phase Flow Computational Conditions

Numerical GridNumerical Grid

Grid type: Structured-MultiblockN° of total Blocks: from 203 to 451Geometry: Fully 3D°N° of total cells: from 994000 to 2450000

Zmax = 750 mm - Xmax = 250 mm - Ymax = 250 mm

Boundary Conditions: AIR Boundary Conditions: AIR

Total Pressure Inlet : 103520 PaTotal Temperature Inlet : 451 KStatic Pressure Outlet : 101300 PaAir Mass Flow Inlet : 0.46 Kg/s

Boundary Conditions: FUEL Boundary Conditions: FUEL

Fuel : Ethyl Alcohol (liquid) Fuel Mass Flow Inlet : 0.0035 Kg/sTotal Temperature Inlet : 293 KDroplets Diameters: 40 Cone Angle : 50°Droplets Velocity : 50 m/s



LPP System : LPP System : Two-Phase Flow Computational Results Two-Phase Flow Computational Results

Z= +100 mmZ= +100 mm

Meridian PlaneMeridian PlaneMesh Size : 994 000Mesh Size : 994 000

Time Dependent Numerical ResultsTime Dependent Numerical Results

Meridian Meridian PlanePlane

Cross Section Cross Section PlanePlane

Mesh Size : 2 450 000Mesh Size : 2 450 000

Locations of measuring traverses



Droplets Trajectories in Cross Section Plane (Z= +100mm)Droplets Trajectories in Cross Section Plane (Z= +100mm)(colour is local velocity level)(colour is local velocity level)



LPP System:LPP System: Droplets Trajectories in Meridian Plane Droplets Trajectories in Meridian Plane(colour is local velocity level)(colour is local velocity level)



Unsteady Droplets’ TrajectoriesUnsteady Droplets’ Trajectories (notice the repeated wall-rebounds, in premixer and in discharge chamber) (notice the repeated wall-rebounds, in premixer and in discharge chamber)



Azymuthally-Averaged Radial Distributions of the Droplets’ Diameters:Azymuthally-Averaged Radial Distributions of the Droplets’ Diameters:Numerical-Experimental Cross ComparisonsNumerical-Experimental Cross Comparisons

Traverse 1

05

101520253035404550

20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80

radial distance [mm]

D32

[u

m]

Experimental

NastComb prediction

Traverse 3

05

101520253035404550

20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80


D32

[u

m]

Experimental

NastComb prediction

Traverse 2

05

101520253035404550

20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80


D32

[u

m]

Experimental

NastComb prediction

Traverse 4

05

101520253035404550

20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80


D32

[um

]

Experimental

NastComb prediction

Locations of measuring traverses

Documents

MUSCLES Modelling of Un s teady Combustion in Low Emission Systems