Environmental Engineering Reference
In-Depth Information
Fig. 7.44 a Stack voltage
and current acquisition versus
time during the dynamic
cycle characterized by the
maximum stack current vari-
ation of 25 A/s. Air manage-
ment strategy N.4.
b Stoichiometric ratio and air
flow rate acquisition versus
time for the experiment (a)
a
80
250
Stack Current
Stack Voltage
75
200
70
150
65
60
100
55
50
50
45
0
0
10
20
30
40
50
Time [s]
b
30
5
4
25
3
20
2
15
Stoichiometric Ratio
Air Flow Rate
1
10
0
0
10
20
30
40
50
Time [s]
Fig. 7.45 C
v
profiles versus
cycle length for the experi-
ments of Figs.
7.42
,
7.43
, and
7.44
4
3,5
2 A/s
10 A/s
25 A/s
3
2,5
2
1,5
1
0,5
0
0
50
100
150
200
250
300
Time, s
This behavior is evidenced in Fig.
7.46
, where the individual cell voltages
corresponding to five significant instants of the cycle are reported, in particular just
before acceleration (t = 0 s), just after acceleration (t = 10 s), two instants of the
stationary phase (t = 20 and 34 s), and at the end of deceleration step (t = 45 s).
An evident problem of stack malfunctioning is observed at t = 10 s, especially for
the last 10 cells, due to difficulties of air compressor in assuring the necessary
