Shock-force mitigation systems and methods for electrochemical fuel cell stacks
Presented are shock-force mitigation systems for fuel cell stacks, methods for making/using such systems, and electric-drive vehicles equipped with such systems. A fuel cell system includes multiple electrochemical fuel cells that are stacked face-to-face along a stack axis to define a fuel cell stack. A push plate abuts each longitudinal end of the fuel cell stack; these push plates translate rectilinearly along the stack axis inside a fuel cell stack housing. An end plate is located in facing spaced relation to each push plate to define a plate pair at each end of the stack. An active or passive force-modifying device is interposed between the two plates in each plate pair; these devices modify stack forces experienced by the fuel cell stack. For an active shock-force mitigation system, each force-modifying device may include a bladder system, spring, and/or linear actuator; an electronic system controller controls activation of the bladders/actuators.
1. A fuel cell system, comprising:
a plurality of electrochemical fuel cells stacked face-to-face along a stack axis to define a fuel cell stack with opposing first and second longitudinal ends;
first and second push plates abutting the first and second longitudinal ends, respectively, of the fuel cell stack and movable along the stack axis;
first and second end plates located in facing spaced relation to the first and second push plates, respectively, to define first and second plate pairs;
first and second force-modifying devices interposed within the first and second plate pairs, respectively, and configured to modify a stack force imparted to the fuel cell stack;
a memory device storing stack aging data associating each of a plurality of fuel cell stack lives with a respective one of a plurality of seal creep levels; and
an electronic system controller connected to the memory device and operable to control the first and second force-modifying devices based on the stack aging data.
2. The fuel cell system of claim 1 , wherein the first and second force-modifying devices include first and second bladder systems or linear actuators, wherein the electronic system controller is communicatively connected to and operable to control the first and second bladder systems or linear actuators.
3. The fuel cell system of claim 2 , further comprising a shock sensor operable to detect onset of a shock event that causes the stack force to be imparted to the fuel cell stack and output a sensor signal indicative thereof to the electronic system controller.
4. The fuel cell system of claim 3 , further comprising an electronic real-time clock operable to track a monitored stack life of the fuel cell stack and output a clock signal indicative thereof to the electronic system controller.
5. The fuel cell system of claim 4 , wherein the system controller is programmed to:
receive, from the shock sensor, the sensor signal indicating onset of the shock event;
responsive to detection of the shock event, determine an estimated degree of fuel cell stack aging using the monitored stack life and the stack aging data;
determine if a severity of the stack force resulting from the shock event reaches a predefined threshold; and
responsive to the severity of the stack force reaching the predefined threshold, transmit a command signal to the first and second bladder systems or linear actuators to modify the stack force based on the estimated degree of fuel cell stack aging.
6. The fuel cell system of claim 5 , wherein the command signal causes the first and second bladder systems or linear actuators to:
decrease the stack force by a first predetermined amount for a first predetermined duration if the degree of fuel cell stack aging is less than a predefined early-stage threshold; and
increase the stack force by a second predetermined amount for a second predetermined duration if the degree of fuel cell stack aging is greater than a predefined late-stage threshold.
7. The fuel cell system of claim 6 , wherein the first and second predetermined amounts and the first and second predetermined durations vary depending on the monitored stack life and the severity of the stack force resulting from the shock event.
8. The fuel cell system of claim 1 , wherein the first and second force-modifying devices include first and second biasing members each compressed between a respective one of the first and second plate pairs.
9. The fuel cell system of claim 8 , further comprising:
a fluid source fluidly connected to the fuel cell stack; and
a fluid injection device controlling injection of fluid from the fluid source into the fuel cell stack,
wherein the electronic system controller is communicatively connected to the fluid injection device and operable to command injection of the fluid into the fuel cell stack at a predefined pressure for a predefined deploy time in response to detection of a shock event causing the stack force.
10. The fuel cell system of claim 8 , further comprising first and second travel limit blocks each located between a respective one of the first and second plate pairs and configured to limit a travel length of the first and second push plates along the stack axis.
11. The fuel cell system of claim 10 , further comprising first and second travel limit shoulders disposed between the fuel cell stack and the first and second push plates, respectively, and configured to limit a travel direction of the first and second push plates along the stack axis.
12. An electric-drive vehicle, comprising:
a vehicle body;
a plurality of road wheels attached to the vehicle body;
a traction motor attached to the vehicle body and operable to drive one or more of the road wheels to thereby propel the electric-drive vehicle;
a fuel cell system attached to the vehicle body and operable to power the traction motor, the fuel cell system including:
a plurality of electrochemical fuel cells stacked face-to-face along a stack axis to define a fuel cell stack with opposing first and second longitudinal ends;
first and second push plates abutting the first and second longitudinal ends, respectively, of the fuel cell stack and movable along the stack axis;
first and second end plates located in facing spaced relation to the first and second push plates, respectively, to define first and second plate pairs; and
first and second force-modifying devices interposed within the first and second plate pairs, respectively, and configured to selectively increase and decrease a stack force imparted to the fuel cell stack;
a memory device storing stack aging data associating a series of fuel cell stack lives each with a respective level of seal creep; and
an electronic system controller connected to the memory device and operable to control the first and second force-modifying devices based on the stack aging data.
13. A method for assembling a fuel cell system, the method comprising:
stacking a plurality of electrochemical fuel cells face-to-face along a stack axis to define a fuel cell stack with opposing first and second longitudinal ends;
abutting first and second push plates against the first and second longitudinal ends, respectively, of the fuel cell stack, such that the first and second push plates are movable along the stack axis;
locating first and second end plates in facing spaced relation to the first and second push plates, respectively, such that the first push plate and the first end plate define a first plate pair and the second push plate and the second end plate define a second plate pair;
interposing a first force-modifying device between the first plate pair and a second force-modifying device between the second plate pair, the first and second force-modifying devices configured to modify a stack force imparted to the fuel cell stack;
connecting an electronic system controller to a memory device storing stack aging data, the stack aging data associating each of a plurality of fuel cell stack lives with a respective one of a plurality of seal creep levels; and
connecting the electronic system controller to the first and second force-modifying devices to control the first and second force-modifying devices based on the stack aging data.
14. The method of claim 13 , wherein the first and second force-modifying devices include first and second bladder systems or linear actuators.
15. The method of claim 14 , further comprising communicatively connecting a shock sensor to the electronic system controller, the shock sensor being operable to detect the onset of a shock event that causes the stack force and output a sensor signal indicative thereof.
16. The method of claim 15 , further comprising communicatively connecting an electronic real-time clock (RTC) to the electronic system controller, the electronic RTC being operable to track a stack life of the fuel cell stack and output a clock signal indicative thereof.
17. The method of claim 13 , wherein the first and second force-modifying devices include first and second biasing members compressed between the first and second plate pairs, respectively.
18. The method of claim 17 , further comprising:
fluidly connecting a fluid source to the fuel cell stack;
fluidly connecting a fluid injection device to the fluid source, the fluid injection device being operable to control injection of fluid from the fluid source into the fuel cell stack; and
connecting the electronic system controller to the fluid injection device, the electronic system controller being operable to command injection of the fluid into the fuel cell stack at a predefined pressure for a predefined deploy time in response to detection of a shock event causing the stack force.
19. The method of claim 16 , wherein the system controller is programmed to:
receive, from the shock sensor, the sensor signal indicating onset of the shock event;
responsive to detection of the shock event, determine an estimated degree of fuel cell stack aging using the monitored stack life tracked by the RTC and the stack aging data stored in the memory device;
determine if a severity of the stack force resulting from the shock event reaches a predefined threshold; and
responsive to the severity of the stack force reaching the predefined threshold, transmit a command signal to the first and second bladder systems or linear actuators to modify the stack force based on the estimated degree of fuel cell stack aging.
20. The method of claim 19 , wherein the command signal causes the first and second bladder systems or linear actuators to:
decrease the stack force by a first predetermined amount for a first predetermined duration if the degree of fuel cell stack aging is less than a predefined early-stage threshold; and
increase the stack force by a second predetermined amount for a second predetermined duration if the degree of fuel cell stack aging is greater than a predefined late-stage threshold.