Fuel Cell Shut-down Time Measurement via Dual Timer Logic
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Solution Overview
Problem
Fuel cell systems face significant degradation due to hydrogen/air fronts during start-up, leading to rapid carbon corrosion and reduced lifespan, as existing solutions like quick hydrogen introduction or slow air purging are insufficient in preventing catalyst and carbon particle degradation.
Innovation Solution
Implementing a method using a stand-by timer and a shut-off timer to accurately determine the shut-down time of a fuel cell system, allowing for optimized gas composition prediction and sequencing during start-up, thereby minimizing hydrogen/air front-induced degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If hydrogen is introduced quickly into the anode flow channels at system start-up, then the time for air removal is reduced, but catalyst and carbon particle degradation occurs due to hydrogen/air front reactions
Solution Approach 1:
The system performs preliminary actions during the shut-down phase by sealing the anode flow channels to trap residual hydrogen and prevent air ingress. This preliminary protection allows the system to start up faster without exposing the catalyst to degrading hydrogen/air front reactions, as the sealed environment maintains hydrogen presence in the anode channels during the critical start-up transition period
2Reliability
If air is purged slowly from the anode flow channels during shut-down, then catalyst degradation is minimized, but the shut-down time increases
Solution Approach 1:
The invention extracts the harmful air from the anode flow channels during shut-down by maintaining a sealed environment that prevents air ingress. Instead of slow purging, the system actively removes air by sealing the channels while hydrogen is still present, then maintains this sealed state during start-up. This extraction approach protects the catalyst from degradation without extending shut-down duration, as the sealing action is rapid rather than gradual
3Reliability
If the anode flow channels are sealed during shut-down to prevent air ingress, then hydrogen/air front degradation is prevented, but the system complexity increases
Solution Approach 1:
The system uses multi-functional existing components (compressor, valves, plumbing) already present in the fuel cell stack to achieve the sealing function. The compressor, which normally supplies air to the cathode, is repurposed to seal the anode channels by redirecting its output. Existing valves and plumbing are configured to enable the sealing mode without requiring entirely new hardware. This universal use of existing components prevents degradation while minimizing the increase in system complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method provides an accurate time count for fuel cell system shut-down, enabling an efficient and safe start-up sequence that reduces catalyst and carbon particle degradation, potentially extending the fuel cell stack's lifetime beyond the current 100 shut-down and start-up cycles.
Implementation Method 1
The engine controller unit enters a shut-down mode upon detection of a key-off event, and a current time value is captured and stored in a non-volatile memory of the engine controller unit
Implementation Method 2
The processor of the engine controller unit is programmed to calculate a time difference between the current time value and a present time value, and the calculated time difference corresponds to the total shut-down time of the fuel cell system
Implementation Method 3
When a fuel cell system is shut down, un-reacted hydrogen gas remains in the anode side of the fuel cell stack. This hydrogen gas is able to diffuse through or cross over the membrane and react with the oxygen in the cathode side.
Implementation Method 4
The fuel cell stack receives a cathode reactant gas, typically a flow of air forced through the stack by a compressor.
Data Source
AI summary
A method for providing an accurate time that a fuel cell system has been shut-down so that the gas constituents in the anode and cathode side of the fuel cell stack can be known for an efficient next system start-up sequence. The method uses two timers, a stand-by timer that provides a time count for how long the fuel cell system has been off, but the vehicle ignition is still on, and a shut-off timer that provides a time count of how long the vehicle ignition has been off. The two time counts are added to give a complete time count of how long the fuel cell stack has been shut-down.