Fuel Cell Pressure-Pulse Purging for Fast Water Removal
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Solution Overview
Problem
Existing fuel cell systems face challenges in efficiently and effectively removing water during purging and drying processes, which can lead to dehydration of the electrolyte membrane and potential mechanical stress, especially during cold starts, requiring a method to minimize membrane dehydration and accelerate the drying process.
Innovation Solution
A method involving increasing and then abruptly reducing purge and back pressures in the fuel cell system using valves to create high flow velocities and shear forces, effectively removing water from the system by converting stored energy into purging pulses, with the option to repeat this process for enhanced efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional purging processes are used during purging and drying mode, then water removal is achieved, but the process takes excessive time and may cause membrane dehydration
Solution Approach 1:
The patent applies periodic action by implementing pulsed purging cycles where the purging valve alternates between open and closed states. During each cycle, pressure builds up in the anode chamber and is then abruptly released, creating repeated pressure pulses that effectively remove water. This periodic operation achieves thorough drying in reduced time compared to continuous low-pressure purging
Solution Approach 2:
The patent changes the pressure parameter dynamically during the purging process. Pressure is increased to a predetermined setpoint during the charging phase, then abruptly reduced to atmospheric pressure during the discharge phase. This parameter change creates high-velocity gas flow that enhances water removal efficiency while controlling the process to prevent membrane dehydration
2Productivity
If high air flow with low humidity is used for cathode side purging, then water removal is achieved, but mechanical stress builds up on the electrolyte membrane
Solution Approach 1:
The patent applies preliminary action by building up pressure gradually to a predetermined setpoint before releasing it. The pressure control unit ensures the pressure reaches the optimal level before the purging valve opens, maximizing the effectiveness of each pressure pulse. This preliminary pressure buildup allows for more controlled and less aggressive water removal compared to immediate high-flow purging
Solution Approach 2:
By using periodic pressure pulses rather than continuous high-flow purging, the patent reduces cumulative mechanical stress on the membrane. The intermittent nature of the pressure pulses allows the membrane to relax between cycles, preventing the buildup of excessive stress that would occur with sustained high-velocity gas flow
3Measurement precision
If measurement technology is used to detect HFR drop for determining purging endpoint, then purging effectiveness is improved, but measurement errors lead to unwanted membrane dehydration
Solution Approach 1:
The patent implements feedback control by using the high-frequency resistance (HFR) measurement to monitor the purging process in real-time. The control unit adjusts the purging duration and intensity based on HFR changes, automatically terminating the process when the membrane reaches optimal dryness. This feedback mechanism eliminates the need for operator judgment and prevents over-drying
Solution Approach 2:
The patent replaces manual or mechanical purging control with an automated electronic control system that uses electrical measurements (HFR) to govern the purging process. This substitution of mechanical control with electronic measurement and control provides more precise and reliable termination criteria, eliminating measurement errors associated with manual methods
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
This method significantly shortens the time required for drying and purging the fuel cell system while minimizing the risk of membrane damage, ensuring a quick, reliable, and component-friendly water removal process.
Implementation Method 1
increasing the purge pressure in the anode portion to a predefined purge pressure setpoint, increasing the back pressure in the cathode portion to a predefined back pressure setpoint and subsequently reducing the increased purge pressure as well the increased back pressure in pulses
Implementation Method 2
converting stored energy into purging pulses... create high flow velocities and shear forces, effectively removing water from the system
Data Source
AI summary
The invention relates to a method for removing water from a fuel cell system (1) comprising a fuel cell stack (2) having an anode portion (3) and a cathode portion (4), a purge valve (5) downstream of the anode portion (3) for controlling a purge pressure in the anode portion (3), and a back pressure valve (6) downstream of the cathode portion (4) for controlling a back pressure in the cathode portion (4), comprising the steps: increasing the purge pressure in the anode portion (3) to a predefined purge pressure setpoint (AP1) with the purge valve (5) closed, increasing the back pressure in the cathode portion (4) to a predefined back pressure setpoint (KP1) with the back pressure valve (6) closed, and subsequently reducing the increased purge pressure as well as the increased back pressure in pulses by opening the purge valve (5) and the back pressure valve (6). Furthermore, the invention relates to a fuel cell system (1) and a computer program product (10) for carrying out a method according to the invention, as well as a storage means comprising a computer program product (10) stored thereon.