Environmental Engineering Reference
In-Depth Information
Fig. 8.24 Different stages of ice formation on the blade before switching the controller on.
a Rime and glaze ice started to form on the blade at t = 0. b Blade slightly covered with rime ice
at t = 17 min. c Blade covered with 5 mm thick rime ice at t = 90 min
20
o
C
V
Ch1
(Volts), 5 Watts/in
2
Heater
Temperature
Ch1
15
10
5
0
Ice starts to melt
-5
-10
0
5
10
15
20
25
30
Time (min)
Fig. 8.25 Time history of voltage and temperature for a selected channel when using distributed
PID control for de-icing, using approximately half of the maximum power capability of the
actuation system with empirically tuned PID gains of K
p
¼
0
:
5 v/(C), K
d
¼
0
:
01 v/(C/s),
K
i
¼
0
:
001 v/(C
s), and closed-loop update rate of 0.5 Hz
the resistive heaters start to increase the local temperature at the leading edge,
2 cm away from the edge of the boundary of the leading edge resistors. Then the
voltage on the resistor decreases as the temperature increases toward the desired
temperature (+2 C). After de-icing and satisfying a no ice condition on both of the
optical channels 1 and 2, the control system automatically shuts down the corre-
sponding resistor 1. This de-icing took about 30 min in an ambient temperature of
