Environmental Engineering Reference
In-Depth Information
Fig. 7.51 a Stack voltage
and current acquisition versus
time during the dynamic
cycle characterized by the
maximum stack current vari-
ation of 50 A/s. Air manage-
ment strategy N.3.
b Stoichiometric ratio and air
flow rate acquisition versus
time for the experiment of (a)
a
80
Stack Current
Voltage Current
250
75
200
70
150
65
100
60
50
55
50
0
0
10
20
30
40
50
60
Time [s]
b
40
5
35
4
30
25
3
20
2
15
10
1
Stoichiometric Ratio
5
Air Flow Rate
0
0
0
10
20
30
40
50
60
Time [s]
Fig. 7.52 C
v
profiles versus
cycle length for the experi-
ments of Figs.
7.50
and
7.51
4
25 A/s
50 A/s
3,5
3
2,5
2
1,5
1
0
10
20
30
40
50
Time, s
ramps the voltage profiles suggest a regular stack operation, with minimum voltage
values always higher than 52 V (Figs.
7.50
aand
7.51
a). Regarding R profiles the
steady state values are reached after\5 s from the beginning of the stationary phase
for both ramps, while an appreciable difference is observed only at the end of the
acceleration step, in particular at 50 A/s a slight and fast reduction (R \ 2) is evi-
denced (Fig.
7.51
b). The calculation of C
v
evidences that this management strategy
makes possible the regular stack working also for 50 A/s, as shown in Fig.
7.52
,in
fact the C
v
values never overcome 2.5 also during the fastest acceleration phase.
