Fuel Cell Air Valve Control for Stop-Mode Voltage Stability
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Solution Overview
Problem
Existing fuel cell systems face issues with wear and tear of rubber lip seals and DC motor brushes in air cut-off valves, leading to inefficiencies and increased costs when transitioning to brushless DC motors, necessitating a new control unit.
Innovation Solution
A system comprising an air cut-off valve and an air pressure control valve, controlled by a unit that adjusts their opening degrees to maintain a predetermined lower limit voltage during fuel cell stop mode, using a bypass flow path and airtight disk structure to optimize air flow and pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the air cut-off valve is repeatedly closed to stop the fuel cell, then the fuel cell can be effectively stopped, but the rubber lip seal is worn out and loses its original function
Solution Approach 1:
The control unit implements periodic opening and closing of the air cut-off valve at predetermined time intervals during fuel cell stop mode. This periodic action allows the valve to maintain voltage within the allowable range while reducing continuous wear on the rubber lip seal compared to repeated closing operations.
Solution Approach 2:
The control unit monitors the fuel cell stack voltage and uses this feedback to determine when to open or close the air cut-off valve. This feedback-based control ensures voltage remains within the allowable range while optimizing valve operation to minimize seal wear.
2Reliability
If the air cut-off valve is controlled to avoid opening degree intervals where the rubber lip seal is worn out, then seal durability is improved, but it is impossible to follow voltage
Solution Approach 1:
The control unit acts as an intermediary that coordinates the operation of the air cut-off valve and air pressure control valve. By using the air pressure control valve to assist in voltage adjustment, the system can maintain voltage control accuracy while the air cut-off valve operates in a manner that reduces seal wear.
Solution Approach 2:
The system dynamically adjusts the opening degrees of both valves based on real-time voltage conditions. The air cut-off valve is controlled to avoid wear-prone opening degrees, while the air pressure control valve compensates to maintain precise voltage following capability.
3Reliability
If a DC motor with motor brush changes to a brushless DC motor, then motor reliability is improved, but it requires a new control unit causing excessive cost increases
Solution Approach 1:
The control unit is designed to perform multiple functions: it controls both the air cut-off valve and the air pressure control valve cooperatively. This multi-functionality allows the existing control unit to work with the modified valve system without requiring a completely new control unit, thereby reducing cost while improving reliability.
Solution Approach 2:
The control functions for the air cut-off valve and air pressure control valve are merged into a single cooperative control system. This integration allows the existing control unit to manage both valves, avoiding the need for separate control units and reducing overall system cost while improving motor and valve reliability.
4Measurement precision
If the air cut-off valve is completely opened to maintain voltage within allowable range, then voltage control is improved, but air supply efficiency decreases
Solution Approach 1:
Instead of completely opening the air cut-off valve, the control unit applies partial action by opening it to the extent necessary to maintain voltage within the allowable range. The air pressure control valve provides additional adjustment capability, allowing precise voltage control without the need for full valve opening, thereby maintaining air supply efficiency.
Data Source
AI summary
An apparatus and a method for controlling air supply into a fuel cell stack are disclosed. The apparatus can include an air cut-off valve that adjusts the air supply into the fuel cell stack, an air pressure control valve that adjusts air pressure supplied to the fuel cell stack, and a control unit that cooperatively controls the air cut-off valve and the air pressure control valve, such that a voltage of the fuel cell stack is maintained as a lower limit voltage if entering a fuel cell stop mode.