Method to correct for permeation uncertainties using a concentration sensor
View Patent ↗A method for determining a rate of accumulation of nitrogen in an anode side of a fuel cell stack. The method includes determining a concentration of nitrogen in an anode loop and determining a number of moles of nitrogen in the anode loop. The method also includes determining a rate of accumulation of nitrogen in the anode loop and determining a permeability factor of nitrogen through fuel cell membranes in the fuel cell stack using the determined rate of accumulation of nitrogen in the anode loop.
1. A method for adapting an anode bleed strategy for a fuel cell stack in a fuel cell system, said method comprising:
determining a concentration of nitrogen in an anode loop of the fuel cell system;
determining a number of moles of nitrogen in the anode loop of the fuel cell system;
determining a rate of accumulation of nitrogen in the anode loop of the fuel cell system;
determining a permeability factor of nitrogen through fuel cell membranes in the fuel cell stack using the determined rate of accumulation of nitrogen in the anode loop of the fuel cell system;
comparing the determined permeability factor of nitrogen to an expected permeability factor of nitrogen to determine a nitrogen permeability gain; and
adapting the anode bleed strategy for the fuel cell system if a predetermined threshold value of the nitrogen permeability gain has been achieved.
2. The method according to claim 1 wherein determining the concentration of nitrogen in the anode loop of the fuel cell system includes determining the concentration of gases in the anode loop using at least one sensor.
3. The method according to claim 1 wherein determining the rate of accumulation of nitrogen in the anode loop of the fuel cell system includes observing the accumulation of moles of nitrogen in the anode loop that occurs between bleed events.
4. The method according to claim 1 wherein determining the permeability factor of nitrogen through the fuel cell membranes in the fuel cell stack using the determined rate of accumulation of nitrogen in the anode loop includes using the equation:
k
N
2
=
2
·
n
.
N
2
·
t
mem
AA
·
N
cell
·
(
P
An
·
(
y
N
2
AnIn
+
y
N
2
AnOut
)
-
P
Ca
·
(
y
N
2
CathIn
+
y
N
2
CathOut
)
where k N 2 is the permeability factor, AA is an active area of the cell, N cell is the number of cells within the fuel cell stack, t mem is a membrane thickness of membrane material that is used to make the membrane of each cell, y N 2 Anin is the concentration of nitrogen in the anode inlet, {dot over (n)} N 2 is the rate of accumulation of nitrogen in the anode side of the stack, P Ca is the pressure of the cathode subsystem, y N 2 CathIn is the concentration of nitrogen in the cathode inlet, and y N 2 CathOut is the concentration of nitrogen in the cathode outlet.
5. The method according to claim 4 wherein the cathode inlet nitrogen concentration and the cathode outlet nitrogen concentration are an assumed value or a measured value.
6. The method according to claim 1 wherein the expected permeability factor of nitrogen is based on a model estimation.
7. A method for adapting an anode bleed strategy for a fuel cell stack in a fuel cell system, said method comprising:
providing an anode bleed schedule based on an expected permeability factor of nitrogen through fuel cell membranes that are between an anode side and a cathode side of fuel cells in the fuel cell stack;
determining a concentration of nitrogen in an anode loop of the fuel cell system;
determining a number of moles of nitrogen in the anode loop of the fuel cell system;
determining a rate of accumulation of nitrogen in the anode loop of the fuel cell system;
determining a permeability factor of nitrogen from a cathode side of the fuel cell stack to the anode side of the fuel cell stack through the fuel cell membranes;
comparing the determined permeability factor of nitrogen to an expected permeability factor of nitrogen to determine a nitrogen permeability gain; and
adjusting the anode bleed strategy for the fuel cell system if a predetermined threshold value of the nitrogen permeability gain has been achieved.
8. The method according to claim 7 wherein determining the concentration of nitrogen in an anode loop of the fuel cell system includes determining the concentration of the gases in an anode loop using at least one sensor.
9. The method according to claim 7 wherein determining the rate of accumulation of nitrogen in the anode loop of the fuel cell system includes observing the accumulation of moles of nitrogen in the anode loop that occurs between bleed events.
10. The method according to claim 7 wherein determining the permeability factor of nitrogen through the fuel cell membranes in the fuel cell stack using the determined rate of accumulation of nitrogen in the anode loop includes using the equation:
k
N
2
=
2
·
n
.
N
2
·
t
mem
AA
·
N
cell
·
(
P
An
·
(
y
N
2
AnIn
+
y
N
2
AnOut
)
-
P
Ca
·
(
y
N
2
CathIn
+
y
N
2
CathOut
)
where k N 2 is the permeability factor, AA is an active area of the cell, N cell is the number of cells within the fuel cell stack, t mem is a membrane thickness of membrane material that is used to make the membrane of each cell, y N 2 Anin is the concentration of nitrogen in the anode inlet, {dot over (n)} N 2 is the rate of accumulation of nitrogen in the anode side of the stack, P Ca is the pressure of the cathode subsystem, y N 2 CathIn is the concentration of nitrogen in the cathode inlet, and y N 2 CathOut is the concentration of nitrogen in the cathode outlet.
11. The method according to claim 10 wherein the cathode inlet nitrogen concentration and the cathode outlet nitrogen concentration are an assumed value or a measured value.
12. The method according to claim 7 wherein the expected permeability factor of nitrogen is based on a model estimation.
13. The method according to claim 7 wherein the amount of adaptation of the anode bleed strategy is dependent on a predetermined threshold value of the nitrogen permeability gain that has been achieved.
14. A method for determining a rate of accumulation of nitrogen in an anode side of a fuel cell stack in a fuel cell system, said method comprising:
determining a concentration of nitrogen in an anode loop of the fuel cell system;
determining a number of moles of nitrogen in the anode loop of the fuel cell system;
determining a rate of accumulation of nitrogen in the anode loop of the fuel cell system; and
determining a permeability factor of nitrogen through fuel cell membranes in the fuel cell stack using the determined rate of accumulation of nitrogen in the anode loop of the fuel cell stack.
15. The method according to claim 14 wherein determining the concentration of nitrogen in an anode loop of the fuel cell system includes determining the concentration of the gases in an anode loop using at least one sensor.
16. The method according to claim 14 wherein determining the rate of accumulation of nitrogen in the anode loop of the fuel cell system includes observing the accumulation of moles of nitrogen between bleed events.
17. The method according to claim 14 wherein determining the permeability factor of nitrogen through the fuel cell membranes in the fuel cell stack using the determined rate of accumulation of nitrogen in the anode loop includes using the equation:
k
N
2
=
2
·
n
.
N
2
·
t
mem
AA
·
N
cell
·
(
P
An
·
(
y
N
2
AnIn
+
y
N
2
AnOut
)
-
P
Ca
·
(
y
N
2
CathIn
+
y
N
2
CathOut
)
where k N 2 is the permeability factor, AA is an active area of the cell, N cell is the number of cells within the fuel cell stack, t mem is a membrane thickness of membrane material that is used to make the membrane of each cell, y N 2 Anin is the concentration of nitrogen in the anode inlet, {dot over (n)} N 2 is the rate of accumulation of nitrogen in the anode side of the stack, P Ca is the pressure of the cathode subsystem, y N 2 CathIn is the concentration of nitrogen in the cathode inlet, and y N 2 CathOut is the concentration of nitrogen in the cathode outlet.
18. The method according to claim 17 wherein the cathode inlet nitrogen concentration and the cathode outlet nitrogen concentration are an assumed value or a measured value.
19. The method according to claim 14 wherein the expected permeability factor of nitrogen is based on a model estimation.
20. The method according to claim 14 wherein the amount of adaptation of the anode bleed strategy is dependent on a predetermined threshold value of the nitrogen permeability gain that has been achieved.