Environmental Engineering Reference
In-Depth Information
frequency fixed for the purge strategy described in the previous paragraphs. Its
pressure changes from 40 kPa at minimum power (0.7 kW) to 34 kPa at maximum
constant power (8.5 kW) and drops to 28 kPa for each purge action.
The profile of the stoichiometric ratio, plotted in Fig.
7.29
, evidences that
R decreases below 1.5 throughout all the fast acceleration phases, indicating
limitations of the compressor to supply enough air in the transient phases, while
resulted 1.9 during steady state phases.
The function of the hydrogen purge and stoichiometric ratio control is high-
lighted in Figs.
7.30
,
7.31
, showing the C
v
values and the individual cell voltages
Fig. 7.28 Hydrogen inlet
pressure versus time during a
sequence of eight fast load
variations from 0.7 to 8.5 kW
0.005
0.004
0.003
0.002
0.001
0
0
150
300
450
600
750
900
Time [s]
5
Fig. 7.29 Stoichiometric
ratio versus time during a
sequence of eight fast load
variations from 0.7 to 8.5 kW
4
3
2
1
0
0
150
300
450
600
750
900
Time [s]
Fig. 7.30 Coefficient of var-
iation (C
v
%) versus time
during a sequence of eight
fast load variations from 0.7
to 8.5 kW
2.5
2
1.5
1
0.5
0
0
150
300
450
600
750
900
Time [s]
