Fuel Cell Ejector Pressure Control via Pump Integration
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Solution Overview
Problem
In fuel cell systems with an ejector downstream a fuel pump, the pressure of the fuel-off gas is often reduced due to inefficiencies in the performance of the ejector and pressure increase ratio, leading to reduced efficiency and increased power consumption, particularly in varying load regions.
Innovation Solution
A fuel cell system configuration that includes a pressure regulating valve upstream of the ejector, a fuel pump in the fuel circulation flow path, and a control means to manage the pressure increase of the fuel gas supplied to the ejector, ensuring the pressure increase ratio between the ejector and fuel pump is set within predetermined ranges based on the fuel cell's operation state, thereby maintaining efficient pressure increase of the fuel-off gas without the need for additional flow paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the ejector is used to circulate fuel using pressure energy, then power consumption is reduced, but the ejector cannot respond to rapid load variations due to nozzle response delay
Solution Approach 1:
The patent combines both the fuel pump and ejector in the fuel circulation system. The fuel pump provides rapid response to load variations, while the ejector operates in parallel to reduce power consumption during steady-state operation. This merging allows the system to leverage the advantages of both devices across different operating conditions.
Solution Approach 2:
The system dynamically switches between fuel pump and ejector operation based on load conditions. The control unit activates the fuel pump during transient conditions requiring rapid response, and relies on the ejector during steady-state operation to minimize power consumption. This dynamic operation optimizes both response speed and energy efficiency.
2Stress or pressure
If the fuel pump increases pressure of fuel-off gas, then circulation is improved, but power consumption increases in operation regions where efficiency is lowered
Solution Approach 1:
The ejector utilizes pneumatic principles by using the pressure energy of the fuel gas itself to drive the circulation of fuel-off gas. The high-pressure fuel gas expands through the nozzle, creating a low-pressure region that draws in and propels the fuel-off gas through the diffuser, eliminating the need for external mechanical power input in steady-state operation.
Solution Approach 2:
The system changes operational parameters by switching between pump-driven and ejector-driven modes based on operating conditions. During transient states, the fuel pump maintains high pressure increase capability. During steady-state operation, the ejector takes over, changing the pressure generation mechanism from mechanical to pneumatic, thereby reducing power consumption while maintaining adequate circulation.
3Reliability
If both fuel pump and ejector are provided to cover different operation regions, then system performance is improved, but device complexity increases
Solution Approach 1:
The control unit serves multiple functions by managing both the fuel pump and ejector operations. It determines operating conditions, selects the appropriate circulation device, and coordinates their operations to optimize system performance across all load regions. This multi-functionality reduces the need for separate control systems for each device.
Solution Approach 2:
The system performs preliminary assessment of operating conditions to determine whether the fuel pump or ejector should be activated. The control unit continuously monitors load variations and proactively switches between devices before performance degradation occurs, ensuring optimal operation throughout transient and steady-state conditions without requiring complex real-time adjustments.
4Stress or pressure
If the ejector performance is not optimized, then pressure of fuel-off gas is reduced, but additional flow paths or components are needed to compensate
Solution Approach 1:
The control unit continuously monitors the pressure and flow conditions of the fuel-off gas and adjusts the operation of the fuel pump and ejector accordingly. When the ejector performance causes pressure reduction, the control system detects this and compensates by adjusting pump operation or switching modes, maintaining optimal pressure without requiring additional hardware 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 configuration ensures that the pressure of the fuel-off gas is efficiently increased across all load regions, simplifying the system and reducing power consumption by preventing pressure loss and optimizing the performance of both the ejector and fuel pump.
Implementation Method 1
an ejector that is provided in the fuel supply flow path, the ejector merging the fuel gas supplied from the fuel supply source with a fuel-off gas exhausted from the fuel cell and supplying the resulting gases to fuel cell
Implementation Method 2
a fuel pump that is provided in the fuel circulation flow path, the fuel pump pressurizing the fuel-off gas in the fuel circulation flow path and sending the fuel-off gas toward the fuel supply flow path
Implementation Method 3
a fuel cell that is supplied with an oxidant gas and a fuel gas as reactant gas and generates electrical power through an electrochemical reaction between the reactant gas
Data Source
AI summary
A fuel cell system including an ejector that merges a hydrogen gas to be supplied from a hydrogen tank to a fuel cell with a hydrogen-off gas exhausted from the fuel cell and supplies the resulting gases to the fuel cell. A hydrogen pump that pressurizes the hydrogen-off gas in a hydrogen circulation flow path and sends the hydrogen-off gas toward a hydrogen supply flow path and a control unit that controls, when the pressure of the hydrogen-off gas in the hydrogen circulation flow path is increased by the ejector and the hydrogen pump, the pressure of the hydrogen gas to be supplied to the ejector and the pressure increase of the hydrogen-off gas realized by the hydrogen pump so that the pressure increase of the hydrogen-off gas realized by the ejector is 0 or higher.