Environmental Engineering Reference
In-Depth Information
Fig. 6.23 C
v
profiles versus
time during a R40 cycle and
b R47 cycle
Fig.
6.28
do not affect the cell uniformity neither during minimum power nor
during transient phases. On the other hand, during R47 the excursions outside the
optimal working region have comparable duration with respect to R40, but the
higher accelerations involved in the cycle determine some peaks of C
v
overcoming
4% in correspondence with the transient phases (Fig.
6.23
b).
A detail of individual cell voltages for the peak at 410 s is shown in Fig.
6.24
,
where three instants are reported, the one just before the acceleration, the time
corresponding to the maximum acceleration, and just after voltage stabilization. It
is possible to observe that several cells are responsible of the C
v
value higher than
4% and that all cells show a lower voltage during acceleration with respect to the
stabilized values.
This behavior seems related to the different dynamic response of stack and air
compressor, as evidenced in Fig.
6.25
a and b, where air flow rate and stack power
