Kwadwo Poku Owusu

Kwadwo Poku Owusu
Department of Mechanical & Manufacturing Engineering
Supervisors: Dr. David C. S. Kuhn & Dr. Eric Bibeau

Outline
� Icing and Icing Measurement
� Research Objectives
� Design Approach
�� EExperimental i t l and d Numerical N i l Procedures P d
� Results and Discussion
� Conclusions

Icing and Icing Measurement
� Atmospheric Icing
� Effects of Icing
� Methods of Ice Detection
�� CCommercial i l I Ice DDetection t ti PProbes b

Atmospheric Icing
� Icing Precipitation
� Icing from Sea Water Spray
� Wet Snow Accumulation
�� IIn‐cloud l d IIcing i
[Ahti 2005]

In‐cloud Icing
� Rime Icing
� ‐5°C 5 to ‐12°C
� Low Liquid Water
Content (LWC)
� Feathery in appearance
� L Low ddensity it

In‐cloud Icing cont’d
� Glaze Icing
� 0°C 0 C to ‐5°C 5 C
� High Liquid Water
CContent t t (LWC)
� Clear in appearance
� High density

Effect of Icing on Wind Turbines
� Decrease of power due to modification in
the h aerodynamics d i of f the h blade bl d
� Increased fatigue of the components due to
imbalance in the ice loads
� Chunks of ice thrown off from the blades
can cause serious injuries to people and
wildlife as well as damage g to property p p y

Methods of Ice Detection
� Direct methods ‐ Detects property change
caused by y the accretion of ice. Such
properties include mass and dielectric
constant
� Indirect methods ‐ Based on detecting
weather conditions that lead to icing such as
humidity or detecting the effect of icing
such suc as reduction educt o in power po e ge generated e ated
[ Homola et. al., 2005 ]

Commercial Ice Detection Probes
� Labko Ice Detector 3210C
� Uses Ultrasonic l i Sensitive S i i
wire to detect icing
� Rosemount Model 0871
LH1 Icing Sensor
� Uses Ultrasonic
Vibrating Probe to
detect Icing
Sensor
part
Control
unit
Vibrating
probe p

Research Objectives
� Develop an ice accretion measurement method suitable for
use on meteorological towers based on the changes in
capacitance and resistance between two electrically
charged cylindrical probes
� Use theoretical models to study the changes in capacitance
with ice accretion, and validate these studies using
“modelled” ice growth in a laboratory setting
� Test the proposed method under simulated rime and glaze
ice conditions in the icing wind tunnel

Design Approach
� Conceptual Design
� Measure ice accretion
based on the changes
in capacitance and
resistance between
two electrically
charged cylindrical
probes during an icing
event
Trajectory of air
Supercooled water drops
Sensing
electric
field

Design Approach cont’d
� Numerical Design
� Design icing probe using QuickField simulations
�� Numerically study the variation of capacitance with simple
geometric “modelled” ice shape to define probe design
� Validate numerical results with experimental results based on
acrylic y model of ice
� Experimental Design and Construction
� Construct an ice accretion probe prototype with ancillary equipment
and define the measurement method based on the numerical design
� Experimental Evaluation
� Test the proposed method under simulated rime and glaze ice
conditions di i in i the h iicing i wind i d tunnel
l

NNumerical i l and d EExperimental i l
Procedure

Numerical Electric Field Simulation:
Governing G i Equations E ti
∂
∂ x
⎛
⎜
⎝
ε
x
ε = x ε y
ρρ
U
=
=
∂ U
∂ x
=
charge
electric
⎞
⎟
⎠
+
∂
∂ x
dielectric
⎛
⎜
⎝
density
potential
ε
y
∂ U
∂ y
constant
⎞
⎟
⎠
=
(C/sq (C/sq.m) m)
(V)
−
ρ

Electric Field Boundary Conditions
� Cylinders are defined as
floating g conductors i.e.
equal but opposite potentials
� U= 0 on the external
boundary
� Dielectric constant of 3.1 for
ice was used
� Charges of ‐1C and +1C are
specified
A typical computation domain

Acrylic Model of Ice
Acrylic cylinder sleeves Aluminum probe with acrylic sleeve

Icing Wind Tunnel
Inner duct of the wind icing tunnel

Probe Orientation
Wind and
supercooled
water drop
direction
d
s
d
s
Wind d aand d
supercooled
water drop
direction
Inline orientation Parallel orientation

Experimental Conditions
Temperature
( o C )
Type of icing
event
Liquid water
content,
‐2 (±2) Glaze 2.0
Ambient
velocity (m/s)
Sensor
orientation
LWC, (g/m 3 ) to ambient
5 (±1)
8 (± 1)
10 (± 1)
5 (±1)
air
1. Inline
2. PParallel ll l
‐10 (± (±2) ) Ri Rime 0.8 8
8 ( ± 1) ) 1. IInline li
10 (±1)
2. Parallel

Schematic of the Probe and Ancillary
Equipment E i t
LLead d wires i
Aluminum
Insulator
Hioki 3522‐50 35 5
Capacitance
meter
RS232 cable
Computer

Results and Discussion

Variation of Capacitance with
Center‐to‐center C Distance Di
Capacitance (pF) (
4.8
4.3
38 3.8
3.3
2.8
2.3
187 1.87 237 2.37 287 2.87 337 3.37 387 3.87
Center -to-center distance,s (cm)
Numerical

Electric Field Distribution
(s=1.87 cm)
Numerical

Capacitance Variation with Electrode
Diameter Di t
4.6
Capacitance C (pF) (
4.4
42 4.2
4.0
3.8
36 3.6
d
s
D
Impinging
water drops
0.89 0.99 1.09 1.19 1.29
Diameter of electrode, D (cm)
Numerical

Capacitance Variation with Ice
Thickness Thi k
Capacitance (pF) (
4.9
4.8
47 4.7
4.6
4.5
44 4.4
inline orientation
parallel orientation
0 0.2 0.4 0.6 0.8 1 1.2
Thickness of modelled ice (cm)
t
Inline orientation
t
PParallel ll l orientation i i
Numerical
t

Capacitance Variation with Size of
Acrylic A li Sleeves Sl
(pF)
Capacitance
5.5
5.0
4.5
4.0
3.5
3.0
25 2.5
acrylic inline case
acrylic parallel case
numerical parallel case
1.27 1.37 1.47 1.57 1.67
Outer diameter of acrylic (cm)
Numerical

Mass M of ice accreted
(g)
Icing Rates for Rime Ice
18
16
14
12
10
8
6
4
2
0
5m/s inline
8 m/s inline
10 m/s inline
5 m/s parallel
8 m/s parallel
10 m/s parallel
Temperature ‐10 o C
LWC 0.8 g/m 3
Thickkness
of ice acccreted
(mm)
14
12
10
8
6
4
5 m/s inline
8 m/s inline
10 m/s inline
5 m/s parallel
8 m/s parallel
10 m/s parallel
0
0 2 4 6 8 10 12 14 16 18 20
0 2 4 6 8 10 12 14 16 18 20
Exposure time (minutes) EExposure pos re time (minutes) (min tes)
Mass Thickness
Standard error bars on the 5 m/s parallel case for both cases
2
Experimental

Mass M of ice acccreted
(g)
Icing Rates for Glaze Ice
35
14
30
25
20
15
10
5
0
5 m/s inline
8 m/s inline
10 m/s inline
5 m/s parallel
8 m/s parallel
10 m/s parallel
Temperature ‐2 o C
LWC 2 g/m 3
0 2 4 6 8 10 12 14 16 18 20
Thickkness
of ice acccreted
(mm)
12
10
8
6
4
5 m/s inline
8 m/s inline
10 m/s inline
5 m/s / parallel ll l
8 m/s parallel
10 m/s parallel
Exposure p time ( (minutes) ) Exposure Time (minutes)
2
0
0 2 4 6 8 10 12 14 16 18 20
Mass Thickness
Standard error bars on the 5 m/s parallel case for both cases
Experimental

Variation of Capacitance with Exposure
Time Ti
Capacitaance
(pF)
5.32
5.12
4.92
4.72
4.52
4.32
4.12
3.92
3.72
3.52
5m/s inline
8 m/s inline
10 m/s inline
5 m/s parallel
8 m/s parallel
10 m/s parallel
13.52
Temperature ‐10 5 / i li
oC Temperature ‐2o Temperature 10 C
12.52 5m/s inline
C
LWC 0.8 g/m3 Temperature 2 C
LWC 2 g/m3 0 2 4 6 8 10 12 14 16 18 20
Exposure time (minutes)
Capacitannce
(pF)
11.52 8 m/s inline
10.52 10 m/s inline
9.52 5 m/s parallel
852 8.52 8 m/s parallel
7.52
6.52
5.52
452 4.52
3.52
10 m/s parallel
0 2 4 6 8 10 12 14 16 18 20
Exposure time (minutes)
Rime ice Glaze ice
Experimental

Variation of Capacitance with Mass and
Thickness Thi k for f Rime Ri ice i
Capacittance
(pF)
5.32
5.12
4.92
4.72
4.52
4.32
4.12
3.92
3.72
3.52
5 m/s inline
8 m/s inline
10 m/s inline
5 m/s parallel
8 m/s parallel
10 m/s parallel
Temperature ‐10o Temperature 10 C
LWC 0.8 g/m3 0 2 4 6 8 10 12 14 16
Mass of ice accreted (g)
Capacittance
(pF)
5.32
5.12 12
4.92
4.72
4.52
4.32
4.12
5 m/s inline
8 m/s inline
10 m/s inline
5 m/s parallel
8 m/s parallel
10 m/s parallel
3.92
3.72
3.52
0 2 4 6 8 10 12 14 16
Thickness of ice accreted (mm)
Mass Thi Thickness k
Experimental

Variation of Capacitance with Mass and
Thi Thickness k f for Gl Glaze iice
Capacitance
(pF)
12.52
11 11.522
10.52
9.52
8.52
7.52
6.52
5.52
4.52
3.52
5 m/s inline
8 m/s inline
10 m/s inline
5 m/s parallel
8 m/s parallel
10 m/s parallel
Temperature ‐2o Temperature 2 C
LWC 2 g/m3 0 5 10 15 20 25 30 35
Mass of ice accreted (g)
Capacitaance
(pF)
12.52
11.52
10.52
9.52
8.52
7.52
6.52
5.52
5 m/s inline
8 m/s inline
10 m/s inline
5 m/s parallel
8 m/s parallel
10 m/s parallel
4.52
3.52
0 2 4 6 8 10 12 14 16
Thickness of ice accreted (mm)
M Mass Thi Thickness k
Experimental

Sensitivity of Probe to Ice Accretion‐
Ri Rime ice i
Capacitannce
per Mass (pF/ /g)
0.14
012 0.12
0.10
0.08
0.06
0.04
0.02
0.00
0 2 4 6 8 10 12 14 16 18 20
Exposure time (Minutes)
per Thickness (ppF/mm)
0.30
5 m/s inline inline00.25 25
8 m/s inline
0.20
10 m/s inline
5 m/s parallel 0.15
8 m/s parallel
0.10
10 m/s parallel
0.05
Capacitance
0.00
0 2 4 6 8 10 12 14 16 18 20
Exposure time (minutes)
Mass Thickness
5 m/s inline
8 m/s inline
10 m/s inline
5 m/s parallel
8 m/s parallel
10 m/s parallel
Experimental, Temperature -10 o C
LWC 0.8 g/m 3

Sensitivity of Probe to Ice Accretion‐
Glaze Gl ice i
Capacitaance
per Mass (ppF/g)
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
0 2 4 6 8 10 12 14 16 18 20
Exposure time (minutes)
Mass
Capacitance perr
Thickness (pF/ /mm)
1.68
5 m/s inline
1.47
8 m/s inline
1.26
10 m/s inline
1.05
5 m/s parallel 0.84
8 m/s / parallel ll l 063 0.63
10 m/s parallel
0.42
0.21
0.00
0 2 4 6 8 10 12 14 16 18 20
Exposure time (minutes)
Thickness
5 m/s inline
8 m/s inline
10 m/s inline
5 m/s parallel
8 m/s parallel
10 m/s parallel
Experimental, Temperature -2 o C
LWC 2.0 g/m 3

Resistance Resistance Variation with with Exposure Exposure
Time
Resiistance
(MΩ)
40
35
30
25
20
15
10
5
0
5 m/s rime ice
8 m/s rime ice
5 m/s / glaze l ice i
8 m/s glaze ice
0 2 4 6 8 10 12 14 16 18 20
Exposure time (minutes)
Experimental

OOptimal ti l PProbe b CConfiguration fi ti
Length of cylinder (cm)
Number of cylinders
Center‐to‐center, s (cm)
Diameter Diameter, d (cm)
Orientation to supercooled
water drops
15
2
1.87 8
1.27
Parallel

Conclusions
� A method based on capacitance and resistance can
be use to detect icing as well as distinguishing
bt between the th two t types t of f in‐cloud i l d iicing i
� The sensitivity of the prototype probe depends on
factors such as center center‐to‐center to center distance distance, size of
probe cylinders and location of the ice deposits
�� The sensitivity of the prototype probe to ice
accretion is high in the first few minutes of exposure
�� The icing rates increased with wind speed

Questions ?