Fuel Cell Air Path Isolation for Pressure Fault Protection
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Solution Overview
Problem
Fuel cell systems face damage due to rapid pressure drops and subsequent undesirable reactions from faults like air path leaks or air compressor malfunctions, which can damage components such as the air compressor and valves, unless pressure is managed to maintain the necessary pressure difference between media systems.
Innovation Solution
The method involves monitoring the air path for faults, closing specific valves to isolate the affected region, reducing pressure in the air path, and adjusting it back to normal levels to prevent damage, while ensuring sufficient air flow to dilute hydrogen concentrations and maintain the pressure difference specification across the fuel cell stack.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the first and second valves are closed to maintain pressure in the blocked region, then the pressure difference specification of the fuel cell stack is met, but the pressure in the air path continues to rise and can cause damage to components
Solution Approach 1:
The air path is divided into two separate regions by closing the first and second valves: a blocked region between the valves that maintains pressure for the fuel cell stack, and an upstream region where pressure can be safely reduced. This segmentation allows independent pressure control in each region, resolving the contradiction between maintaining pressure difference specification and preventing high pressure damage.
Solution Approach 2:
The harmful high pressure is extracted from the upstream air path by opening the bypass valve, allowing pressure to be reduced in this region while the blocked region maintains its required pressure. This separates the harmful effect from the necessary function.
2Object-affected harmful factors
If the pressure in the air path is rapidly reduced by opening the bypass valve, then components are protected against high pressure damage, but the hydrogen concentration in the off-gas line may not be sufficiently diluted
Solution Approach 1:
The bypass valve is opened in advance to reduce pressure before the purge valve is activated. This preliminary pressure reduction ensures that when purging occurs, the hydrogen concentration can be safely diluted without creating high pressure conditions, thus preventing both high pressure damage and hydrogen accumulation hazards.
Solution Approach 2:
The system uses periodic purging cycles where the purge valve is activated at specific intervals to dilute hydrogen concentration in the off-gas line, coordinated with the pressure reduction phase. This periodic action ensures hydrogen dilution while maintaining safe pressure levels.
3Object-generated harmful factors
If the purge valve is opened to dilute hydrogen concentration, then safety is improved, but the pressure in the air path increases which can damage components
Solution Approach 1:
By maintaining closed first and second valves during purging, the system segments the air path so that the blocked region maintains stable pressure while the purge operation occurs in the recirculation circuit. This prevents pressure increase in the fuel cell stack region while still achieving hydrogen dilution through the purge valve.
4Stress or pressure
If the air compressor capacity is increased to maintain air supply, then the pressure ratio increases causing higher pressure in the air path, but reducing capacity allows pressure reduction which may insufficiently supply air to the fuel cell stack
Solution Approach 1:
The air compressor is segmented into two operational modes: during fault conditions, it operates to maintain air supply to the fuel cell stack through the blocked region while the bypass valve handles pressure reduction in the upstream region. This allows the compressor to focus on quantity of air supply while pressure management is handled separately by the bypass system.
Data Source
AI summary
The invention relates to a method for protecting components of a fuel cell system (1), the fuel cell system (1) having a fuel cell stack (101), an air path (10), an off-gas line (12), and a fuel line (20) with a recirculation circuit (50), the method comprising the steps of:monitoring the air path (10) for a fault;closing a first valve (61) which is situated in the air path (10) and closing a second valve (62) which is situated in the off-gas line (12);blocking a purge valve (41);reducing the pressure in the air path (10) upstream of the first valve (61);if further operation of the fuel cell system (1) is possible:increasing the pressure in the air path (10) upstream of the first valve (61);unblocking the purge valve (41);opening the first valve (61) and the second valve (62);further operating the fuel cell system (1).