Fuel Cell Ejector Control With Parallel Injectors at Low Current
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Solution Overview
Problem
Low current operation in fuel cell systems challenges the efficient recirculation of excess hydrogen due to insufficient pressure difference and inaccurate flow measurement, leading to reduced cell stability and increased pressure fluctuations, which can shorten the lifespan of the fuel cell stack and its components.
Innovation Solution
Implementing multiple parallel injectors that work collaboratively to control hydrogen flow velocity and quantity, allowing for asynchronous injection termination, which eliminates the need for a pump or blower and reduces pressure fluctuations, ensuring consistent humidity delivery and extended component lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single injector is used to deliver hydrogen to the nozzle, then the device complexity is reduced, but the pressure fluctuations increase and cell stability decreases
Solution Approach 1:
The single injector is segmented into multiple parallel injectors (first injector, second injector, third injector) that deliver hydrogen to the nozzle independently. This segmentation allows for distributed flow control, reducing pressure fluctuations and improving cell stability while maintaining manageable system complexity through modular architecture.
Solution Approach 2:
The system changes the operational parameters by enabling asynchronous injection termination among the parallel injectors. The controller can close each injector at different times based on real-time pressure and flow requirements, optimizing hydrogen delivery and stabilizing cell operation without requiring complex mechanical modifications.
2Reliability
If pump or blower is added to enhance hydrogen recirculation, then the hydrogen delivery reliability is improved, but the parasitic power consumption increases
Solution Approach 1:
The system uses the kinetic energy of the hydrogen stream itself to drive recirculation through the ejector effect. The high-velocity hydrogen from the nozzle creates a low-pressure region that draws unconsumed hydrogen back through the recirculation loop, eliminating the need for external pumps or blowers and avoiding associated parasitic power consumption.
Solution Approach 2:
The ejector utilizes pneumatic principles where the accelerated hydrogen stream from the nozzle creates a pressure differential that drives the recirculation of excess hydrogen. This passive pneumatic recirculation system replaces active mechanical pumping, reducing energy losses while maintaining reliable hydrogen delivery to the anode side.
3Quantity of substance
If the injection pulse duration is extended to ensure sufficient hydrogen delivery, then the hydrogen quantity is improved, but the pressure fluctuations increase and component lifespan is reduced
Solution Approach 1:
The system employs periodic injection pulses with optimized duration and timing across multiple parallel injectors. By distributing the total hydrogen quantity requirement across several shorter, coordinated pulses from different injectors, the system achieves sufficient hydrogen delivery while reducing peak pressure fluctuations and extending component lifespan.
Solution Approach 2:
The controller enables partial injection by closing individual injectors at different times during the injection pulse sequence. This allows the system to deliver the required hydrogen quantity through coordinated partial actions of multiple injectors rather than extending a single injection pulse, thereby minimizing pressure fluctuations and reducing mechanical stress on components.
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 approach enhances the fuel cell system's efficiency by maintaining stream momentum, reducing parasitic power consumption, and increasing the lifespan of both the fuel cell stack and injectors by minimizing pressure pulses and injection cycles.
Implementation Method 1
The ejector has a nozzle configured to accelerate and direct the hydrogen into the mixing chamber
Implementation Method 2
The ejector defines a mixing chamber having an outlet that is in fluid communication with the anode side. The ejector has a nozzle configured to accelerate and direct the hydrogen into the mixing chamber
Implementation Method 3
The fuel cell stack is configured to generate power to propel the vehicle. The fuel cell stack has an anode side
Implementation Method 4
The recirculation loop is configured to direct unconsumed hydrogen from the fuel cell stack to the mixing chamber
Data Source
AI summary
A vehicle includes a fuel cell stack, an ejector, a first injector, a second injector, and a controller. The fuel cell stack is configured to generate power to propel the vehicle. The fuel cell stack has an anode side. The ejector is configured to deliver hydrogen to the anode side. The ejector has a nozzle configured to accelerate and direct the hydrogen toward the anode side. The first and second injectors are configured to deliver hydrogen to the nozzle. The controller is programmed to, in response to a command to deliver hydrogen to the anode side, open each of the first and second injectors and subsequently close the second injector while the first injector remains open.