“Large Eddy Simulations of Ethanol Spray Combustion”. Flavio Galeazzo – EP/USP

Laboratory of Thermal and Environmental EngineeringCombustion Research Center

Large Eddy Simulations of

Ethanol Spray Combustion

Dr.-Ing. Flavio Cesar Cunha Galeazzo, [email protected]

Prof. Dr.-Ing. Guenther Carlos Krieger Filho

3. Workshop de High Perfomance Computing 17. April 2015


Experimental setup

PhD of Newton K. Fukumasu (2010 - 2014)

Open burner derived from an automotive fuel injector and a swirler

Laser diagnostics (PDI, LIF e PIV)

3WHPC-LCCA Flavio Galeazzo 2


100 Hz 250 Hz 400 Hz

Case Injection

frequency

Duty

cycle

Combustion pattern

ESF100 100 Hz 29% Long anchored flame

ESF250 250 Hz 43% Short anchored flame

ESF400 400 Hz 59% Lifted flame

Boundary conditions

Air flow 20 m3 / h

Ethanol flow 2 L / h


Numerical setup

OpenFOAM 2.1.1

LES (Large Eddy Simulation)

Smagorinsky subgrid scale model (SSG)

Spray

Lagrangian particle tracking

Combustion model

Simple “mixed is burned” approach




Grid 1 Grid 2

Number of elements 600 000 1.6 million

Grid sensitivity

Hexahedral elements

Two grids with different refinement

Cold flow

Better agreement with refined grid

Grid 2 was used for the LES simulations


• Cold flow

• Mean axial velocity UX at the centerline

• Experiments

• RANS simulation using Reynolds-stress turbulence model

• LES using Smagorinky SSG

• The negative velocities indicate the recirculation zone created by the swirl flow

• Much better agreement with LES



• Combustion

• Axial velocity(m/s)

• Temperature (K)


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100 Hz 250 Hz 400 Hz

• Experiment chemiluminescence

• Mean temperature (K)


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Computational resources

BlueGene/P – USP/Rice

42 racks, 128 CPUs, 512 computing cores each

4 GB per CPU

Proprietary interconnect

SGI Altix cluster – LETE

12 nodes, dual CPU, 8 computing cores each

24 GB per node / 12 GB per CPU

Infiniband interconnect

Problems using BG/P

Compilation of OpenFOAM in the BG/P

Need GCC compiler – can’t use native IBM XL compiler

Need shared libraries – complicated to setup in the BG/P

Run the OpenFOAMsimulation in the BG/P

Need aprox. 2.5 GB per grid partition

Can’t use all computing cores of each CPU



Performance comparison

BlueGene/P – USP/Rice

42 racks, 128 CPUs, 512 computing cores each

4 GB per CPU

Proprietary interconnect

SGI Altix cluster – LETE

12 nodes, dual CPU, 8 computing cores each

24 GB per node / 12 GB per CPU

Infiniband interconnect

SwirlFlameLETE/1/H1/les_onlyFlow – cold flow

Grid = 1.6 million elements

ModeNumber of

partitions

Simulation

time (s)

Computing

time (s)

Relative

time

Blue

Gene/PSMP 128 0,002 517 1

LETE openmpi 24 0,002 450 0,87

SwirlFlameLETE/1/H1/EPS250/les_fireFoam - combustion

Grid = 1.6 million elements

ModeNumber of

partitions

Simulation

time (s)

Computing

time (s)

Relative

time

Blue

Gene/PSMP 128 0,002 8423 1

Blue

Gene/PSMP 256 0,002 6077 0,72

Blue

Gene/PSMP 384 0,002 5892 0,70



Conclusions

Better agreement of LES results with the experimental data

More refined computational grids and longer simulation time are required for LES

For more refined grids there is a need of more computational power

OpenFOAM 2.1 was successfully compiled in the BlueGene/P

The performance is not ideal

Old GCC compiler (version 4.3.2, from 2008)

Memory usage of OpenFOAM do not permit the use of all computing cores

Use of OpenMP is an alternative

Current development, up to now no speedup using Paralution OpenMP solver

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Thank you

Dr.-Ing. Flavio Cesar Cunha Galeazzo, [email protected]

Prof. Dr.-Ing. Guenther Carlos Krieger Filho

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Technology

“Large Eddy Simulations of Ethanol Spray Combustion”. Flavio Galeazzo – EP/USP