Mixture Formation of Diesel Sprays and Effect of Heat ... · Xray, Argone Nozzle geometry ......

Mixture Formation of Diesel Sprays

and Effect of Heat Release on the Velocity Field

G. Bruneaux, L.M. Malbec IFP Energies Nouvelles, Rueil Malmaison, France

L. Pickett,Sandia National Laboratories, Livermore, CA, USA

IFPEN 2/33Gilles Bruneaux

Introduction

• Designing fuel efficient, low exhaust emission reciprocating

engines requires a detailed understanding of the physical

phenomena

– Mixing of air and fuel is one of the most decisive phenomena

• Study of air entrainment/mixture formation in Diesel jets

– High complexity:

• strong coupling between the contributing mechanisms

– fuel evaporation, turbulence, small scale mixing...

– Requirement:

• coupled quantitative measurement of several parameters such

as flow velocities and mixing characteristics

– The harshness of the environment (high pressure and

temperature, presence of liquid droplets...) is such that the

effort to develop quantitative optical diagnostics is enormous

• Such a work has been performed within the ECN

collaboration at Spray A condition

– Advanced mixture fraction measurements at Sandia

– Advanced velocity field measurements at IFPEN


Presentation plan

• The Engine combustion Network

• Experimental apparatus (IFPEN and Sandia)

• Experimental techniques

• 1D spray model

• Results

– Mixture Field

– Velocity field

– Combined

– non reacting vs reacting

• Conclusion


What is the Engine Combustion Network?

• An internet library for data storage intended to be used

for CFD model improvement and validation at engine

condition

• An experimental and modeling collaboration dedicated

to improving understanding and predictive capability of

engine/spray CFD models.

see www.sandia.gov/ECN


ECN research involves specific target conditions. Why?

• Opportunity for the greatest exchange and deepest collaboration.

• Leverages the development of quantitative, complete datasets.

• Pathway towards predictive spray and engine CFD.

900 K, 60 bar90° C, 1500 barSpray AInjector Ambient

Internal nozzle

geometry

• Spray H (baseline n-

heptane)

• Spray B (3-hole version

of Spray A).

• Spray G (Gasoline) and

engine targets TBD.

Other defined targets:


Spray A Database

• Low-temperature combustion condition relevant to engines that use moderate EGR

• 5 nominally identical injectors donated by Bosch and shared between the ECN

partners

• >26 different measurements performed by >8 different institutions

– Sandia, IFPEN, CMT, CAT, Argone, TU/e, Duisburg Essen, Meiji University...

Number of holes single hole – axial

Fuel injection pressure 1500 bar, prior to start of injection

Fuel n-dodecane

Fuel temperature at nozzle 363 K (90°C)

Injection duration 1.5 ms

Ambient gas temperature 900 K

Ambient gas pressure near 6.0 MPa

Ambient gas density 22.8 kg/m3

Ambient gas oxygen (by volume) 15% O2

Already available onthe websiteExp. Done, to be published

Planned

Considered

Needle lift motionXray, Argone

Nozzle geometrySandia/CAT/Argone

Standard: liq & vap penetration, lift off, AIMie/Shadowgraphy/SchlierenSandia/IFPEN/CAT/CMT/TUe

Dense liquid densityXray at ambientArgone

Fuel concentrationRayleighSandia

VelocityPIV, IFPEN

Soot fv, sizeLII, TEM IFPEN, Sandia

Combustion structureCH2O & OH LIFIFPEN, TUe 2013

Missing

Droplet size

Transparent visualisations

Temperature

Other species

Ballistic imagingChalmers (date?)

Rate of injection/MomentumCMT


The control of boundary conditions

• Experiments performed in many different kinds of facilities, and in many

different places in the world!

SandiaCMTCaterpillar IFPEN TU/e


The control of boundary conditions

• Direct measurement of boundary conditions

– ambient temperature, density, fuel temperature

• Characterization of the behavior of the Diesel spray issued from one of the 5

single hole injectors supplied by Bosch using ECN standard diagnostics

– Diffused Back illumination (liquid penetration), Schlieren (vapor penetration),

direct visualization (auto-ignition), OH chemiluminescence (lift off length)

• Since the difference between injectors is known, it is used to determine the

degree of accuracy of the boundary conditions

– measurements are consistent with different

types of HP-HT facilities

IFPEN 9/33Gilles Bruneaux9

• PrecombustionC2H4/C2H2+H2+N2+O2 CO2+H2O+N2+O2

• Sapphire windows

• IFPEN: 160bar, 1500K, 30kg/m3

• Sandia: 350bar, 1500K, 60kg/m3

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8Temps après étincelle, [s]

4.0

6.0

8.0

10.0

12.0

14.0

Pre

ssio

n ce

llule

, [M

Pa]

400

600

800

1000

1200

1400

1600

Tem

péra

ture

, [K

]

T

P

Experimental apparatus

IFPEN

SANDIA


� High speed time-resolved PIV (10000 Hz)

� Camera Photron SA1

� YAG Laser 532nm (approx. 2mJ per pulse)

� Seeding particle: zirconium oxide <5µm

Experimental setups: Velocity fields

YAG LASER 532nm






� Average fields on 20 injections


YAG LASER 532nm

t

4µs

100µs

Im 2 Im 1 Im 2 Im 1Im 1 Im 2

Spray velocities

Surrounding air velocities

⇒On a single injection event, 2 ranges of velocities can be resolved

Spray velocities (approx. 50m/s)

Surrounding air velocities (5m/s)


• example of combined images


internal flow

dt=4µs

external flow

dt=100µs


• example of combined images


+

=


� Rayleigh scattering

� Camera PIXIS 1024B, high sensitivity

� YAG Laser 532nm (150mJ per pulse)

� Correction algorithm for particle

contamination, flare, ...

� In Spray A conditions only mean images are

provided as final results due to noise on

single shot images (particle contamination),

average on about 20-40 images

Experimental setups: Mixture fraction fields

See SAE 2007-01-0647

IFPEN experience

of Rayleigh scattering....


MIE

nnnn----heptane/DCSF ambientheptane/DCSF ambientheptane/DCSF ambientheptane/DCSF ambient

Adiabatic mixingAdiabatic mixingAdiabatic mixingAdiabatic mixing ((((Espey et al. [1996])

• Measure both IR,a, IR,j

– Allows in-situ calibration for IR,a variation

in laser sheet intensity

– Beam-steering or divergence addressed

by using IR,a on bottom and top

• Measurement provides

– Mixing: Na / Nf

– Temperature

mix

a

fa

faaf

aR,

jR,

T

T

/NN1

/NN/σσ

I

I

++=

)/NN(T famix f=

55=σσ af /

20 30 40 50 60

-10

-5

0

5

10

Distance from Injector [mm]

700

800

900

1000

[K]

Raw image

Nf/Na

Tmix

20 30 40 50 60

-10

-5

0

5

10


700

800

900

1000

[K]20 30 40 50 60

-10

-5

0

5

10

20 30 40 50 60

-10

-5

0

5

10


700

800

900

1000

[K]

Raw image

Nf/Na

Tmix

1000 K42 bar

See SAE 2007-01-0647

Rayleigh Molecular CrossRayleigh Molecular CrossRayleigh Molecular CrossRayleigh Molecular Cross----SectionsSectionsSectionsSections

Experimental setups: Mixture fraction fields

IFPEN 16/33Gilles Bruneaux 16/23

• In 1996, Naber and Siebers used control-

volume analysis to predict diesel jet

penetration and mixing (SAE 960034).

• Some assumptions:

– Non-vaporizing, isothermal

– Injection rate and ambient are steady

– Uniform velocity and fuel volume-fraction

profiles

– Constant spreading angle (adjusted)

– Fuel velocity = entrained gas velocity

+++++= 22 ~

161~

4ln16

1~161

4

~

2

~~ SSS

SSt

1~161

2~~

2 ++=

xtd

xd

• Apply conservation of mass and momentumto derive analytical solution for velocity and jet penetration:

• Excellent prediction of experimental penetration and tip velocity over wide range of conditions

1D Spray model: control volume analysis for steady jets

IFPEN 17/33Gilles Bruneaux 17/23

• In 2009, this 0D model was improved by M. Musculus to account for transients

• Non-steady jets can be solved using an array of discrete control volumes and computer-numerical integration.

� Solve mass and momentum transport between control volumes.

� The spray angle remains an input of the domain

� Gaussian profiles are assumed for mixture and velocity

1D Spray model: Discrete Control Volume Analysis

see SAE 2009-01-1355


• Rate of injection

– Bosh method rate-meter characterizations at

CMT

• Spray momentum

– Specifically designed test rig at CMT

• Angle

– Obtained from best fit match of ECN Spray A

Shlieren vapor penetration characterizations

1D Spray model: Input parameter from ECN data


Parametric variations

PIV

(IFPEN)

Rayleigh

(SNL)

22.8kg/m3 – 900K – 150MPa – 0% O2 x x

22.8kg/m3 – 900K – 100MPa – 0% O2 x x

22.8kg/m3 – 900K – 50MPa – 0% O2 x

15.2kg/m3 – 1100K – 150MPa – 0% O2 x

15.2kg/m3 – 900K – 150MPa – 0% O2 x

22.8kg/m3 – 900K – 150MPa – 15% O2 x


� Radial profiles of axial velocity in steady-state, Spray A

-10 0 100

20

40

60

80

100

d = 25mm

Distance to axis of the spray (mm)

Ve

loci

ty (

m/s

)

-10 0 100

20

40

60

80

100

d = 30mm


Ve

loci

ty (

m/s

)

-10 0 100

20

40

60

80

100

d = 35mm


Ve

loci

ty (

m/s

)-10 0 100

20

40

60

80

100

d = 40mm


Ve

loci

ty (

m/s

)

-10 0 100

20

40

60

80

100

d = 45mm


Ve

loci

ty (

m/s

)

-10 0 100

20

40

60

80

100

d = 50mm

Distance to axis of the spray (mm)V

elo

city

(m

/s)




� Radial profiles of mixture fraction in steady-state, Spray A

-10 0 100

0.05

0.1

0.15

0.2

d = 25mm


Mix

ture

Fra

ctio

n (

-)

-10 0 100

0.05

0.1

0.15

0.2

d = 30mm


Mix

ture

Fra

ctio

n (

-)

-10 0 100

0.05

0.1

0.15

0.2

d = 35mm


Mix

ture

Fra

ctio

n (

-)

-10 0 100

0.05

0.1

0.15

0.2

d = 40mm


Mix

ture

Fra

ctio

n (

-)

-10 0 100

0.05

0.1

0.15

0.2

d = 45mm


Mix

ture

Fra

ctio

n (

-)

-10 0 100

0.05

0.1

0.15

0.2

d = 50mm


Mix

ture

Fra

ctio

n (

-)


� Injection pressure variation: 150MPa and 100MPa


Injection pressure:

- Great impact on velocity

- Almost no impact on mixture fraction (as expected): the entrained air mass flow

rate is proportional to the injection mass flow rate

20 30 40 50 600.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

Distance to nozzle tip (mm)

Mix

ture

Fra

ctio

n (

-)

150MPa

100MPa

Radial profile at 30mm


� Ambient density variation: 22.8kg/m3 and 15.2kg/m3


Ambient density:

- Great impact on velocity AND mixture fraction

- Less air is entrained => higher mixture fraction and faster penetration

20 30 40 50 600

0.05

0.1

0.15

0.2


Mix

ture

Fra

ctio

n (

-)

22.8kg/m3

15.2kg/m3

Radial profile at 30mm


15 20 25 30 35 40 45 50 55 60 650.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18


Mix

ture

fra

ctio

n (

-)

15 20 25 30 35 40 45 50 55 60 6520

30

40

50

60

70

80


Ve

loci

ty (

m/s

)

Rayleigh

PIV

Consistency of the results

Spray Model

Boundary Conditions

+

Vapor angle

from ECN Spray A

� Can PIV and Rayleigh scattering results, coming from different institutions, be

used as a unique database?

� Is the 1D spray model predictive and consistent with these two databases

PIV


� Axial profiles of velocity and mixture fraction


Axial velocity Mixture fraction


� Radial profiles of axial velocity and mixture fraction at Spray A conditions


-10 0 100

0.05

0.1

0.15

0.2

d = 25mm


Mix

ture

Fra

ctio

n (

-)

-10 0 100

0.05

0.1

0.15

0.2

d = 30mm


Mix

ture

Fra

ctio

n (

-)

-10 0 100

0.05

0.1

0.15

0.2

d = 35mm


Mix

ture

Fra

ctio

n (

-)

-10 0 100

0.05

0.1

0.15

0.2

d = 40mm


Mix

ture

Fra

ctio

n (

-)

-10 0 100

0.05

0.1

0.15

0.2

d = 45mm


Mix

ture

Fra

ctio

n (

-)

-10 0 100

0.05

0.1

0.15

0.2

d = 50mm


Mix

ture

Fra

ctio

n (

-)


Predictions from the spray model are within the precision of the

measurements, both for axial velocity and mixture fraction

⇒These 2 sets of data thus appear to be consistent

⇒The hypothesis of the 1D spray model are validated


� Effect of parametric variations: Effect of injection pressure and density



Same conclusions

injection pressure: 1000bar

ambient density: 15.2kg/m3




� +532nm short band pass optical filter



Experimental setup for reacting conditions

YAG LASER 532nm


Non reacting Reacting

Comparison Non-reacting Versus reacting


reacting

non reacting

� Significant expansion is observed

� increase of axial velocities

� increase of jet width


Non reacting

Reacting


Non reacting

Reacting


� Air entrainment velocities are significatively

lower in reacting conditions


CONCLUSIONS

• The 1D spray model is able to predict quantitatively the main spray

characteristics (average mixture fraction and velocity fiels) within the

measurement uncertainty

• Main hypothesis validated/dominant processes identified:

• The mixing process and flow dynamics of the spray are driven by the

mass flow rate and mass momentum

• The velocity and mixture fraction profiles are Gaussian

• A consistent database can be built using advanced diagnostics performed by

different institutions (when boundary conditions are well know, ie ECN)

• In reacting conditions, the flow is significantly modified (expansion, reduced

air entrainment)

• Next steps:

• Identify the physical processes hidden in the spray angle

• how can we be truly predictive?

• key challenges: understand the relation between internal nozzle

flow and near field spray structure

• Turbulence/flame interaction

Mixture Formation of Diesel Sprays and Effect of Heat ... · Xray, Argone Nozzle geometry ......

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Transcript of Mixture Formation of Diesel Sprays and Effect of Heat ... · Xray, Argone Nozzle geometry ......