Fuel Cell Hydrogen Purging via Dynamic Ejector Control
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Solution Overview
Problem
In fuel cell stacks, the low flow rate of hydrogen during low current generating modes can lead to fuel starvation and impurity accumulation, affecting electrical power production and the lifespan of the stack due to insufficient flow to push impurities through the system.
Innovation Solution
A system comprising an anode supply, ejector, purging arrangement, bypass valve, and controller that controls the flow and pressure of the hydrogen stream to remove impurities and maintain optimal hydrogen recirculation, using a blower to increase flow in low current modes and bypassing it in high current modes to manage water and nitrogen levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If hydrogen flow rate is reduced during low current generating mode, then energy consumption is decreased, but impurity removal capability deteriorates and fuel starvation occurs
Solution Approach 1:
The system dynamically adjusts the hydrogen flow rate based on the operating mode of the fuel cell stack. During low current generating mode, the controller reduces the flow rate to save energy, while during high current mode, it increases the flow rate to ensure adequate impurity removal and prevent fuel starvation. This dynamic adjustment resolves the contradiction by adapting the flow rate to actual operational requirements.
Solution Approach 2:
The controller changes the flow rate parameter according to the current generating mode. By monitoring the operating conditions and adjusting the flow rate parameter accordingly, the system maintains reliable impurity removal during high demand while reducing energy consumption during low demand periods, thus resolving the technical contradiction between energy efficiency and reliability.
2Reliability
If hydrogen flow rate is increased during high current generating mode, then impurity removal capability is improved, but energy consumption increases
Solution Approach 1:
The system employs dynamic control where the hydrogen flow rate is increased only when the fuel cell stack operates in high current generating mode. The controller monitors the operating conditions and adjusts the flow rate accordingly, ensuring adequate impurity removal during high demand while avoiding unnecessary energy consumption during low demand periods.
Solution Approach 2:
The controller adjusts the flow rate parameter based on the current generating mode. During high current mode, the parameter is increased to enhance impurity removal capability, while during low current mode, it is reduced to minimize energy consumption. This parameter adaptation resolves the contradiction between reliability and energy efficiency.
3Productivity
If unused hydrogen is recirculated to the fuel cell stack, then fuel efficiency is improved, but impurity accumulation occurs due to insufficient flow rate
Solution Approach 1:
The system dynamically controls the recirculation of unused hydrogen based on the operating mode. During low current generating mode, the controller reduces the recirculation flow rate to prevent impurity accumulation and fuel starvation, while during high current mode, it maintains adequate recirculation to improve fuel efficiency. This dynamic adjustment resolves the contradiction between fuel efficiency and reliability.
Solution Approach 2:
The controller adjusts the recirculation flow rate parameter according to the current generating mode. By changing this parameter, the system optimizes fuel efficiency during high demand while preventing impurity accumulation and fuel starvation during low demand, thus resolving the technical contradiction.
4Reliability
If blower is activated to increase hydrogen flow during low current mode, then impurity removal is improved, but device complexity increases
Solution Approach 1:
The controller acts as an intermediary that manages the blower operation. It activates the blower only when necessary during low current generating mode to enhance impurity removal, and deactivates it during high current mode when natural flow is sufficient. This intelligent control reduces the need for complex continuous flow management systems while maintaining reliability.
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 system ensures efficient hydrogen recirculation and purging, preventing fuel starvation and cell corrosion, while optimizing blower efficiency by adjusting flow rates based on current generation modes, thereby enhancing fuel cell performance and longevity.
Implementation Method 1
The ejector is configured to combine a purged fuel stream and the supply fuel stream for generating the input fuel stream
Implementation Method 2
a number of fuel cells are joined together to form a fuel cell stack... provides electrical current in response to electrochemically converting hydrogen and oxygen into water
Implementation Method 3
The nitrogen may cross over into the unused hydrogen by diffusion through a membrane in the fuel cell from a cathode side
Data Source
AI summary
A system for delivering an input fuel stream to a fuel cell stack to generate electrical current and to discharge an unused fuel stream is provided. A supply produces a supply fuel stream. An ejector combines a purged fuel stream and the supply fuel stream and controls the flow of the input fuel stream to the fuel cell stack.A purging arrangement receives the unused fuel stream which includes impurities and purges the impurities from the unused fuel stream to generate the purged fuel stream.A bypass valve is capable of delivering the purged fuel stream to the ejector. A blower is capable of delivering the purged fuel stream to the ejector. A controller controls one of the bypass valve and the blower for delivering the purged fuel stream to the ejector based on the amount of electrical current generated by the fuel cell stack.