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Planar laser-Induced Fluorescence - Eucass

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Equivalence Ratio Measurements in Kerosene-Fuelled

Kerosene Fuelled

LPP Injectors using Kerosene Planar Laser-Induced

Laser Induced

Fluorescence

Mikaël Orain, Orain Björn Rossow, Rossow,

Frédéric Grisch

Physics, Instrumentation and Sensing Department

91761 Palaiseau - France


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Research on Aircraft propulsion

Industrial Context

Increasing the performance of aircraft combustors (LPP, RQL systems) to

respect future pollutant regulations

P = 3 MPa, T air = 900 K

Better understanding of:

• Spray dynamics and evaporation

• Fuel/air mixing

• Pollutant formation

Improving injection systems better fuel/air mixing

Kerosene vapour imaging

• Combustion instabilities and Flashback


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Objective

Identification of fluorescent tracers for kerosene vapour imaging using

Planar laser-Induced Fluorescence (PLIF)

Kerosene (Jet A1): multicomponent system

- aliphatic hydrocarbon compounds (C 9 to C 16 )

- aromatics

Tracer Properties:

- naturally present in kerosene Experimental conditions :

Spectroscopic experiment :

- Spectroscopic study of kerosene

- Identification of the fluorescent species

Implication for laser diagnostic:

- Gaseous flow

- Two-phase flow

Heated Cell experiment

Temperature range : 400 K to 750 K

Excitation wavelength : 266, 282, 308 nm

Pressure range : 1 to 7 bar

Oxygen quenching (buffer gas: N 2 , Air)


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Setup for kerosene spectroscopy

Kerosene

tank

liquid

mass flowmeter

Controlled

Evaporator

and

Mixer

P = 10 bar

Heating

Gas

Mixture of cell

mass flowmeter

Kerosene vapour

and carrier gas

Concentration

controlled

Absorption

photodiode

Temperature

& pressure

controlled

Laser

Fluorescence

PC

Spectrograph

CCD camera

Molar fraction of kerosene vapour ≈ 0.3 % Spectral resolution ≈ 1 nm

Laser energy < 0.6 mJ/pulse to minimize photolysis of kerosene (~10 9 W/cm²/pulse.)


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Results on kerosene spectroscopy

Fluorescence (a.u.)

Fluorescence (a.u.)

Kerosene fluorescence

280 320 360 400 440

Wavelength (nm)

T=170°C, P=1bar, N 2

Jet A1

280 320 360 400 440

Wavelength (nm)

T=170°C, P=1bar, N 2

Jet A1

1,2,4-Trimethylbenzene

Fluorescence (a.u.)

Identification of fluorescent species

• Tracers naturally present in kerosene

• Definition of a mixture of 4 aromatics

spectrally equivalent to kerosene

T=170°C, P=1bar, N 2

Jet A1

Naphthalene

280 320 360 400 440

Wavelength (nm)

Mono-aromatics fluorescence Di-aromatics fluorescence

+

1-methylnaphtalene

1,3-dimethylnaphtalene


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Results on kerosene spectroscopy

Fluorescence (a.u.)

0.20

0.15

0.10

0.05

1

440 K

570 K

670 K

0.00

260 280 300 320 340 360 380 400 420 440

Wavelength (nm)

Temperature dependence of kerosene

fluorescence spectrum in N 2 at 0.1 MPa

2

overall Fluorescence (a.u.)

40

30

20

10

1

0

400 450 500 550 600 650 700

Temperature (K)

Temperature dependence of kerosene

integrated fluorescence in N 2 at 0.1 MPa

Different dependence for the two fluorescence bands with temperature

Potential for temperature measurements

2


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Results on kerosene spectroscopy

Fluorescence (a.u.)

0,20

0,15

0,10

0,05

1

0,00

260 280 300 320 340 360 380 400 420 440

2

Wavelength (nm)

X02=0

X02=0.01

X02=0.04

X02=0.21

Dependence of kerosene fluorescence spectrum

upon O 2 molar fraction at 440 K, 0.1 MPa

I 0 /I - 1

40

30

20

10

440 K

570 K

670 K

0

0,00 0,03 0,06 0,09 0,12 0,15 0,18 0,21

[O 2 ]

Behaviour of the first fluorescence band,

0.1 MPa

Different behavior for the two fluorescence bands with [O 2 ]

Potential for equivalence ratio measurements


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for PLIF equivalence ratio measurements

Collection of the kerosene fluorescence on different spectral domains

Instantaneous measurement of temperature, species concentration and equivalence ratio

• Excitation at 266 nm

• Detection with two ICCD cameras

• Spectral filtering of fluorescence

T

1

0,8

0,6

0,4

0,2

0

Filter 1

1

2

Filter 2

260 280 300 320 340 360 380 400 420

Longueur dʹonde (nm)


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Equivalence ratio measurements in gaseous flow

Preheated turbulent N 2 jet (650 K) seeded with kerosene (0.16 %)

Mixture fraction

Kerosene molar fraction Oxygen molar fraction

Detectivity : 1 ppm at 650 K and 0.1 MPa, in air

50 ppm at 700 K and 1.5 MPa, in air


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ratio measurements in two-phase flows

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Lean Premixed Prevaporised injector

Laser sheet

Test rig

Inlet temperature : 500 - 730 K

Overall equivalence ratio Φ 0 : 0.12 - 0.61

Pressure : 0.1 - 1 MPa

Re : 20000 - 30000

LPP

system

Fluorescence of liquid and vapour phases of kerosene


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Equivalence ratio measurements in two-phase flows

Data processing

Fluorescence of kerosene (liquid and vapour)

Kerosene droplet

Fluorescence of kerosene vapour

Intensity

20000

15000

10000

5000

Raw intensity

Corrected intensity

0

0 10 20 30 40 50

Pixel N°

Correction for removing droplet fluorescence


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ratio measurements in a LPP injector

1) T=500 K, Φ 0 =0.12

LPP

system

Single-shot measurement

LPP

system

Φ∼0.55 Φ 0

maps of local equivalence ratio

averaged measurement


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Equivalence ratio measurements in a LPP injector

2) Influence of inlet temperature (Φ 0 =0.44)

LPP

system

LPP

system

T=580 K T=650 K

Single-shot maps of local equivalence ratio


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Equivalence ratio measurements in a LPP injector

High temperature leads to: - larger droplet evaporation rate

LPP

system

Φ∼0.35 Φ 0

T=580 K

- longer stratification length

LPP

system

Φ∼0.55 Φ 0

T=650 K

Maps of local equivalence ratio (average over 200 images)


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Conclusion – Future Prospects

Conclusion

Development of PLIF-kerosene for equivalence ratio measurements in multiphase flows:

- Demonstration on a preheated kerosene/N 2 jet

- Specific processing for two-phase flows

- Application to an LPP injector at 0.1 MPa for evaporating conditions

Future prospects

- Extension of the database at higher temperature and pressure

- Modelling of kerosene fluorescence:

Prediction of fluorescence dependence at high temperature

- Application to an LPP injector at real operating conditions (3 MPa, 900 K)

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