Fuel Cell Hydrogen Circulation Using Injector-Ejector Valve Switching
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Solution Overview
Problem
In fuel cell systems using a circulation system with an injector and a linear solenoid valve, the suction amount of fuel off-gas by the ejector decreases at low output levels, leading to insufficient hydrogen circulation and accelerated fuel cell performance degradation due to inadequate hydrogen supply.
Innovation Solution
A fuel cell system with a circulation system that includes an injector, a linear solenoid valve, and an ejector, where the linear solenoid valve operates at a higher opening degree than planned when the output is low to increase fuel gas and off-gas circulation, ensuring a minimum hydrogen amount is maintained, and the injector and solenoid valve are used in specific output regions to secure the necessary hydrogen threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the linear solenoid valve is used to supply fuel gas at low output levels, then the fuel gas supply is steady and proportional to the opening degree, but the injection pressure becomes lower than when the injector operates, causing the ejector suction amount to decrease and hydrogen circulation to be insufficient
Solution Approach 1:
The system dynamically switches between injector and linear solenoid valve based on output amount thresholds. The control device determines the output amount of the fuel cell and selectively operates the injector for low output amounts and the linear solenoid valve for high output amounts, optimizing performance across different operating conditions
Solution Approach 2:
The system changes the operating parameters by switching between two different valve types with different flow characteristics. The injector provides high-pressure intermittent flow for low output, while the linear solenoid valve provides steady proportional flow for high output, adapting the fuel gas supply parameters to match the required hydrogen circulation needs
2Quantity of substance
If the injector operates with intermittent flow to supply fuel gas, then the injection pressure is high and ejector suction is effective, but the valve requires pulse control and opening-closing operation which is more complex than linear control
Solution Approach 1:
The control system is segmented into two distinct valve control paths: one for the injector using pulse control for low output amounts, and another for the linear solenoid valve using linear control for high output amounts. This segmentation allows each valve to operate in its optimal control mode without requiring the other to be overly complex
3Loss of energy
If the linear solenoid valve opening degree is kept low at small output amounts, then the fuel gas consumption is reduced, but the injection pressure drops and the ejector cannot secure the necessary circulation gas amount
Solution Approach 1:
The system uses two different valve technologies with different characteristics rather than attempting to optimize a single valve across all operating conditions. The injector is used for low output amounts where high pressure is needed, and the linear solenoid valve is used for high output amounts where steady flow is needed, avoiding the need to compromise either valve's performance
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 secures the necessary hydrogen amount for fuel cell operation, preventing performance deterioration and ensuring appropriate scavenging, even at low output levels, by increasing the circulation flow of off-gas and maintaining the hydrogen stoichiometric ratio.
Implementation Method 1
the ejector suctions the fuel off-gas depending on the injection pressure, mixes the fuel off-gas with the fuel gas, and introduces the mixture into the fuel cell
Data Source
AI summary
An injector of a fuel cell system operates when the output amount of a fuel cell is in a first output region, and a linear solenoid valve operates when the output amount of the fuel cell is in a second output region. When the output amount of the fuel cell is in a third output region that is included in the second output region, the linear solenoid valve opens at such a degree that fuel gas and fuel off-gas necessary to secure a hydrogen amount threshold that is a smallest hydrogen amount necessary for operation of the fuel cell are capable of being introduced from an ejector into the fuel cell.