Characterization of fuel spray for a marine burner back-spill …orbit.dtu.dk/files/148850665/Cafaggi_IFRF_2018... · 2018-06-06 · marine burner back-spill atomizer Giovanni Cafaggi*

Characterization of fuel spray for a marine burner back-spill atomizer

Giovanni Cafaggi*

Co-Authors:

Peter Arendt Jensen

Peter Glarborg

Sønnik Clausen

Kim Dam-Johansen

* Corresponding author: [email protected]

DTU Chemical Engineering, Technical University of Denmark

Agenda

30 May 20182

• Introduction to the project

• Spray characterization setup

• Selected results

• Conclusions and future work

DTU Chemical Engineering, Technical University of Denmark 30 May 20183

Background

Project goals:

• Support the development of a new burner:

– Lower NOx emissions

– Multi-fuel capability

• Set up reliable CFD simulations to evaluate further improvements


CFD background and contribution

2% CO surface,fuel droplets in black

Temperature

0

10

20

30

40

50

60

70

80

90

100

0

5

10

15

20

25

0 50 100 150 200

Num

ber

of

dro

ple

ts [

%]

Dro

ple

t m

ean d

iam

ete

r [µ

m]

Distance from the nozzle [mm]

Simulated droplet evaporation

Mean diameter

Evaporated Droplets

• Sensitivity to droplet size

and velocity.

• Range for experimental

spray measurements.


Spray setup commissioning

30 May 20185

• CFD showed that the flame stability is highly dependant from the droplet size and velocity distributions.

• The setup has been built for direct measurements of both using optical imaging methods.

• The setup is able to reproduce the operating conditions of the atomizer in the full scale boiler (matching flows and operating pressures, spill-return nozzle).


Pump

Tap water

Tank

Pressuregauge 1

Nozzle holder

Nozzle

Spray

Pressuregauge 2

Safety valve

Membrane tank

Flowmeter 1

Flow meter 2Backpressure

valve 2

Backpressure valve 1

Spray setup

30 May 20186

Nozzle section

Setup PID

Working nozzle


Spray setup – measurement technology

• Led pulser (1μs), ccv camera, stereoscopic lens (2.5 μm resolution)

• Pairs of images to find droplet velocities

• Image analysis with in-house software

7

2.41mm

3.24mm

0.86mm

F. Cernuschi et al. 2017 [4]

30 May 2018

Imaging system

Observed volume

Pair of images 1 µs apart



8


2.41mm

3.24mm

0.86mm




30 May 2018

Imaging system

Observed volume







9

2.41mm

3.24mm

0.86mm


30 May 2018

Imaging system

Observed volume




10


2.41mm

3.24mm

0.86mm




30 May 2018

Imaging system

Observed volume



Images Extracted data

Spray setup - PostprocessingNumber based particle size distribution

at 15 mm radial distance

Droplet pairing criteria:

• Area

• Sharpness

• Position


Images Extracted data

Droplet pairing and analysis

Spray setup - PostprocessingNumber based particle size distribution

at 15 mm radial distance


Spray setup - Results

30 May 201813

• Experimentally based data:

– Droplet velocity distribution

– Droplet density distribution

– Droplet size distribution

– Droplet volume fraction distribution

– Partial flow behaviour


Spray setup - results

30 May 201814







0

5

10

15

20

25

30

0 50 100 150 200

Velo

city m

agnitude [

m/s

]

Distance from injection [mm]

Average droplet velocity from spray setup simulations and experiments

SS distance based

SS volume based

experiments

transient distance based

transient volume based

Preliminary spray setup CFD transient simulation








0

20

40

60

80

100

120

0 10 20 30 40 50 60

SMD


30 May 201815

66% load

Experimental results match the simulation regarding the stratification

of droplets according to their size

Simulations

Experimental measurements

33% load

100% load

[μm

]

Angle with spray axis [o]

Droplets diameters


0.00E+00

5.00E-05

1.00E-04

1.50E-04

2.00E-04

0 10 20 30 40 50 60

Volume fraction


16








[μm

][#

]

[-]

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60

Droplet in each image

0

20

40

60

80

100

120

0 10 20 30 40 50 60

SMD

30 May 2018

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60

Average velocity

[m/s

]



0.00E+00

5.00E-05

1.00E-04

1.50E-04

2.00E-04

0 10 20 30 40 50 60

Volume fraction


17








[μm

][#

]

[-]

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60


0

20

40

60

80

100

120

0 10 20 30 40 50 60

SMD

30 May 2018

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60

Average velocity

[m/s

]



0.00E+00

5.00E-05

1.00E-04

1.50E-04

2.00E-04

0 10 20 30 40 50 60

Volume fraction


18








[μm

][#

]

[-]

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60


0

20

40

60

80

100

120

0 10 20 30 40 50 60

SMD

30 May 2018

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60

Average velocity

[m/s

]



0.00E+00

5.00E-05

1.00E-04

1.50E-04

2.00E-04

0 10 20 30 40 50 60

Volume fraction


19








[μm

][#

]

[-]

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60


0

20

40

60

80

100

120

0 10 20 30 40 50 60

SMD

30 May 2018

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60

Average velocity

[m/s

]



0.00E+00

5.00E-05

1.00E-04

1.50E-04

2.00E-04

0 10 20 30 40 50 60

Volume fraction


20








[μm

][#

]

[-]

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60


0

20

40

60

80

100

120

0 10 20 30 40 50 60

SMD

30 May 2018

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60

Average velocity

[m/s

]



0.00E+00

5.00E-05

1.00E-04

1.50E-04

2.00E-04

0 10 20 30 40 50 60

Volume fraction


21








[μm

][#

]

[-]

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60


0

20

40

60

80

100

120

0 10 20 30 40 50 60

SMD

30 May 2018

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60

Average velocity

[m/s

]




30 May 201822







0

5

10

15

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25

30

35

0 25 50 75 100 125 150 175


0

20

40

60

80

100

120

0 25 50 75 100 125 150 175

SMD

0.00E+00

5.00E-05

1.00E-04

1.50E-04

2.00E-04

0 25 50 75 100 125 150 175

Volume fraction

Angle scaled on highest coverage [%]

[μm

][#

]

[-]

0

5

10

15

20

25

30

35

0 25 50 75 100 125 150 175

Average velocity

Angle scaled on highest coverage [%]

[m/s

]


Conclusions

• Measurements at different loads showed that it has little effect on particle size,

droplet concentration and volume fraction distribution.

• On the other hand, spray cone angle and velocity are heavily affected by

changes in load.

• Even if the volume fraction is low, there is a large number of droplet in the

hollow part of the cone.

• Data from the spray setup matched expectations and CFD simulations

23 30 May 2018


Future work

• Further experiments should be carried out to observe spray characteristics at

various axial distances and to check if the CFD results are matched also further

away from the nozzle.

• Spray setup improvements to avoid droplet recirculation and avoid liquid spills

• Water/glycerol solutions with surfactants for the spray setup (viscosity and

surface tension): design of model fluids to evaluate spray characteristics of

different fuels

24 30 May 2018


Thank you for your attention

Documents

Characterization of fuel spray for a marine burner back-spill …orbit.dtu.dk/files/148850665/Cafaggi_IFRF_2018... · 2018-06-06 · marine burner back-spill atomizer Giovanni Cafaggi*