determination of flow patterns by image analysis of a

2017 NETL Workshop on Multiphase Flow Science

Determination of Flow Patterns by Image Analysis of a

Rectangular Spouted Bed

By: Jingsi Yang, Steven Rowan,

Ronald Breault, Justin Weber.Fluid Particle Science and Engineering Group

August 9, 2017

1

2Contents

• Introduction

• Experimental systems

• Current research objectives:

Flow pattern observation

Image preliminary processing

Bed height determination

Bed expansion ratio

• Future focuses:

Jet size and voidage determination

• Conclusions

3Introduction-Spouted phenomenon

Fountain

Bed surface

Annulus

Spout

Gas inlet

For a vessel filled with coarse particles, when the gas isinjected vertically through a centrally located opening, theresulting high-velocity jet leads to a stream of particlesrising rapidly in a hollowed central core within the bed ofparticles. Particles carried above the bed surface, rain backon the annular region between the hollowed core andthe column wall.

A composite of a dilute phase central core with upward-moving solids entrained by a concurrent air flow and adense phase surrounding with downward particle flow.

4

Hydrodynamics in spouted beds have been characterized extensively by optical fiber systems andpressure fluctuation analysis. With the development of high speed video cameras and imaginganalysis methods, an alternative method based on image analysis was proposed to study thehydrodynamics in a rectangular spouted bed in this study.

Cavity formation Internal spout development Onset of external spout

Increasing fluid flow rate

Introduction-Evolution of typical spouting process

5Experimental systems-Spouted bed & visualization apparatus

Spouted bed

Images Analysis Diffusion

Panel

30.2 mm

Backup light

Video Camera

Dequ = 9.6 mm Dequ = 12.7 mm

Air

Spouted bed

Filter

75 ° Cone

Slotted nozzle

ΔP3

ΔP2

ΔP1

101.6 mm

30.2 mm

Pressure transducer

3.8 mm

19.1 mm 25.4 mm

25.4 mm

6.6 mm

19.1 mm

25.4 mm

25.4 mm

6Flow pattern observation

Alumina

Nylon

Static

Static

Expansion External spoutingBubble development

Jet development External spouting Increasing gas flow rate

7Image preliminary processing

(a)

(b)

(c)

(d)

(e)

Preprocessing for the following processes

Image (c) Image (d)

Logical operation

Image (e)

9

Original Cropped grayscale Binary Extracted binary

Bed height determination

10

0 150 300 450 600 750 900100

120

140

160

180

200

220

240

260

Deriv

ative

of a

vera

ge in

tens

ity (-

)

Pixels (-)

Average intensity 2nd Derivative of average intensity

-20

0

20

40

60

80

100

Aver

age

inte

nsity

(-)

Bed surface

Bed bottom

Bed surface

Bed bottom

Bed height

Bed height determination-Demonstration and examples

12

0.0 0.4 0.8 1.2 1.60.070

0.075

0.080

0.085

0.090

Alumina0.00962 m nozzle0.0762 m Static bed height

Bed

heig

ht (m

)

Superficial gas velocity (m/s)0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

0.0

0.3

0.6

0.9

1.2

1.5 Bed pressure drop Bed expansion ratio

Superficial gas velocity (m/s)Be

d pr

essu

re d

rop

(KPa

)

0.95

1.00

1.05

1.10

1.15

1.20

Bed expanded

Spouted bed

Alumina 0.00962 m nozzle

Bed

exp

ansio

n ra

tio (-

)

0.0762 m Static bed height

Internal spout External spout

Packed bed

Minimum spouting velocity

External spouting velocity

① ② ③

Bed height determination-Demonstration and examples

13

① ② ③

0.0 0.5 1.0 1.5 2.00.95

1.00

1.05

1.10

1.15

1.20

1.25Alumina0.00962 m nozzle

Bed

expa

nsio

n ra

tio (-

)

Superficial gas velocity (m/s)

0.0762 m 0.102 m 0.127 m (0.98,1.14) (1.31,1.15)

(1.20,1.14)

0.0 0.5 1.0 1.5 2.00.95

1.00

1.05

1.10

1.15

1.20

1.25Alumina0.0127 m nozzle

Bed

expa

nsio

n ra

tio (-

)


0.0762 m 0.102 m 0.127 m

(0.98,1.20) (1.52,1.22)(1.31,1.22)

15Bed expansion ratio-Alumina

1.14

1.21

At the onset of the external spout, the bed expanded the same ratio regardless of the static bed height.The expansion ratio varies with the size of nozzles.

16Bed expansion ratio-Nylon

0.0 0.5 1.0 1.5 2.0 2.50.95

1.00

1.05

1.10

1.15

1.20

1.25

1.30

1.35

1.40

(1.52,1.32)

(1.41,1.32)

Nylon0.00962 m nozzle

Bed

expa

nsio

n ra

tio (-

)


0.0762 m 0.102 m 0.127 m

(1.09,1.34)

1.32

0.0 0.5 1.0 1.5 2.0 2.50.95

1.00

1.05

1.10

1.15

1.20

1.25

1.30

1.35

1.40Nylon0.0127 m nozzle

Bed

expa

nsio

n ra

tio (-

)


0.0762 m 0.102 m 0.127 m

(1.63,1.31)

(1.85,1.31)

(1.20,1.33)

1.32

At the onset of the external spout, the bed expanded the same ratio regardless of the static bed heights and nozzle sizes.

17Bed expansion ratio-The effect of nozzle size

The effect of nozzle size on the bed expansion ratio of Alumina is more significantly than that of Nylon.

1.0

1.1

1.2

1.3

1.4

1.0

1.1

1.2

1.3

1.4

0.0 0.5 1.0 1.5 2.0 2.5

1.0

1.1

1.2

1.3

1.4

H0= 0.0762 m 0.00962 m 0.0127 m

Nylon

H0= 0.102 m

Bed

expa

nsio

n ra

tio (-

)

H0= 0.127 m


1.001.051.101.151.201.25

1.001.051.101.151.201.25

0.0 0.5 1.0 1.5 2.00.951.001.051.101.151.201.25

H0= 0.0762 m Alumina 0.00962 m 0.0127 m

H0= 0.102 m

Bed

expa

nsio

n ra

tio (-

)

H0= 0.127 m


18Future focuses- Jet size & voidage determination

The jet with a certain geometrical shape and a relatively clear boundary can be determined.

(1) (2) (3) (4)

Jet contour

Bounding box

Jet contour (particles & air)

Jet area, Sjet; Bounding box(Jet heights & width, Hjet & Wjet)

Jet area equivalent diameter, Djet

𝐷𝐷𝑗𝑗𝑗𝑗𝑗𝑗 = 2s ∗𝑁𝑁𝜋𝜋

where N is the pixel number occupied by the jet; s is ratio of m/pixel.

Void area ratio, Rv𝑆𝑆𝑎𝑎𝑎𝑎𝑎𝑎𝑆𝑆𝑗𝑗𝑗𝑗𝑗𝑗

= Equivalent jet voidage, εv

𝑆𝑆𝑎𝑎𝑎𝑎𝑎𝑎 𝑆𝑆𝑎𝑎𝑎𝑎𝑎𝑎𝑆𝑆𝑗𝑗𝑗𝑗𝑗𝑗 𝑆𝑆𝑗𝑗𝑗𝑗𝑗𝑗

=𝐷𝐷𝑎𝑎𝑎𝑎𝑎𝑎3

𝐷𝐷𝑗𝑗𝑗𝑗𝑗𝑗3=

19Conclusions

Based on a systematic of image processing

procedures, an alternative method was proposed to

study the hydrodynamics in a rectangular spouted

bed.

Different flow patterns were observed:

Flow regime transformation was complicated;

Under the same static bed height, the flow

regime was changed with the increase of

superficial gas velocity.

Bed expansion ratio indicated the external spout

velocity, which was helpful to determine flow

regime.

High speed video

Original images

Threshold & logical operations

Jet size/penetration depth

Typical flow pattern

Bed expansion ratio

Jet Voidage

Video extraction

Adaptive threshold & blank image &

Mask

Calculation of jet area

Bed height calculation

Calculation of air/void area

in the jet

Polygon ROI cropping

Dilation & erosion

Denoising

Self-defined aglorism

Jet contour

20Conclusions

The variation of bed expansion ratios with superficial gas velocity were shown for Alumina and

Nylon particles using two different nozzle sizes (0.00962 m and 0.0127 m):

At the onset of the external spout, the bed expanded the same ratio regardless of the static

bed heights under the same nozzle size for both particles;

Comparing to Nylon, the bed expansion ratio of Alumina at the onset of the external spout

was influenced more significantly by the nozzle size.

Future focuses:

Determination of jet sizes and voidage, and fountain height by applying image analysis;

Different parameters such as cone angle, property of bed materials;

Flow regime map construction.

21Acknowledgements

Dr. Ronald Breault (Mentor);

Justin Weber (Research Advisor);

Steve Rowan;

Michael Bobek;

Nicholas Hillen;

Sam Bayham;

determination of flow patterns by image analysis of a

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