development of an intrusive array probe sensor for ... 4a to 7a/4a2 coombes james.pdf · probe...

Development of an Intrusive Array Probe Sensor for Monitoring Particle Size, Velocity and Concentration in a

Coal/Biomass Multi-phase Flow By

James Coombes Under supervision of:

Professor Yong Yan Of

Contents • Introduction to the array probe sensor concept

• Motivation of research

• State of current research

• Operating principal of electrostatic sensors

• Current design of the array probe sensor

• Testing and results

Testing facilities at the University of Kent

Experimental results

• Conclusion

• Future plans

Motivation of Research • Being able to online monitor the pulverized fuel in real time for the

whole cross section of the pipe before it enters the furnace would allow more effective control systems to be developed to improve efficiency of the burning process consequently reducing emissions and fuel consumption

• The ability to practically measure the complex parameters inside a multiphase flow for validation of CFD (Computational Fluid Dynamic) models

State of Current Research

Particle Velocity

Particle Concentration

Particle Size Distribution

Electrostatic ● ● ●

Capacitive ● ●

Digital Imaging ● ● ●

Piezoelectric ● ●

Radiometric ● ●

Ultrasonic ●

Array Probe Sensor Concept

Array Probe Sensing Area

Advantages: • Sensing area covers cross section of pipe • Simple to install on existing systems • Able to measure particle velocity,

concentration and particle size

Disadvantages: • Intrusive

Particle Velocity Using Electrostatic Sensors

Yan et al. (1995) Meas. Sci. Tech.

𝑉𝑒𝑙𝑜𝑐𝑖𝑡𝑦 =𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒

𝑇𝑖𝑚𝑒

Current Sensor Design Electrostatic Sensor Array

Mounting Spool • 2” Pipe Bore compatible

with both test rigs in the University of Kent

• Either vertical or horizontal orientation for sensor

Electrostatic Sensor Array

Current Sensor Design

Mounting Spool • 2” Pipe Bore compatible

with both test rigs in the University of Kent

• Either vertical or horizontal orientation for sensor



Array Electrodes • 5 pairs of electrodes set

10mm apart to improve correlation coefficient

• Electrodes are formed on PCB (0.8mm) simplifying manufacture


Array Sensor Housing • Earthed housing to reduce

noise in pre-amp • Small cross sectional area

only 2.5mm thick • 45 degree knife edge on the

leading edge to deflect impacting particles away from sensing electrodes

• Eventually will be ceramic coated to improve durability


Current Sensor Design Block diagram of Electrostatic Sensor

Array Measurement System

Testing Positive Pressure Pneumatic Bulk Solid Conveyor

Test Rig

Currently being modified for use with pulverised coal

Adjustable Vacuum plant to convey pulverised material around the system.

Adjustable vibration feeder for input of powdered material.

Removable horizontal pipe spool for mounting sensors

Removable Vertical pipe spool for mounting sensors

Testing Negative Pressure Bulk Solid Conveyor Test Rig

Particle flow

Material Under Test

(Pulverised coal will be tested in the future)

Pulverised Biomass Pellets

0

5

10

15

20

25

30

Equ

ival

ent

Vo

lum

e (%

)

Particle Size (um)

Particle Size Distribution

Biomass Pellets (Spruce/Pine)

Typical Electrode Output

-1.5

-1

-0.5

0

0.5

1

1.5

0 1 2 3 4 5 6 7

Ou

tpu

t Si

gnal

(V

)

Time (ms)

Electrode Output Signals

Upstream

Downstream

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

0 1 1 2 2 3 3

Co

rrel

atio

n F

un

ctio

n

Time (ms)

Cross Correlation

Results - Horizontal Pipe

0

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10 15 20 25

Pip

e C

ross

Sec

tio

n (

mm

)

Velocity (m/sec)

Velocity Profile 0°

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Pip

e C

ross

Sec

tio

n (

mm

)

RMS Charge Level (%)

RMS Profile 0°

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Material Under Test Pulverised biomass fuel

pellets (Spruce/Pine)



0

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50

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Pip

e C

ross

Sec

tio

n (

mm

)

Correlation Coefficient

Correlation Coefficient Profile 0°

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Pip

e C

ross

Sec

tio

n (

mm

)

Standard Deviation of Correlation Coefficient (%)

Standard Deviation Profile 0°

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e C

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Velocity (m/sec)


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e C

ross

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RMS Profile 90°

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e C

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)



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Results - Vertical Pipe



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Pip

e C

ross

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RMS Profile 0°

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0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

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e C

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n (

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0.00

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Results - Vertical Pipe



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Pip

e C

ross

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tio

n (

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0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

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e C

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Conclusion • Experimental data collected from tests carried out on the horizontal

pipe clearly show that the electrostatic cross sectional array sensor is capable of measuring the velocity profile and particle concentration profile on a developed air/solid flow.

• Data collected on the vertical pipe does not show a developed velocity profile due to the proximity of the sensor to the pipe bend. However the particle concentration profile shows that the particle concentration is highest along the pipe wall due to the centrifugal forces of the particles traveling in the pipe bend.

• Correlation coefficient values stay constant for the cross section of the pipe on both horizontal and vertical with exception to 0° horizontal where the quality of the coefficient improves in the centre of the pipe and more turbulence closer to the pipe wall caused by gravity.

Future Plans • Incorporate piezoelectric impact sensors onto the sensor array

and investigate coating the sensor in a ceramic material to improve durability

• Conduct experiments using coal and coal/biomass mixtures.

• Construct an array sensor for a larger pipe diameter for testing on an industrial system (coal fired power station)

Thank you for your time.

Do you have any question?

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