Dual-Ejector Fuel Cell Startup Purging for Inert Gas Removal
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Solution Overview
Problem
Existing fuel cell systems face challenges in quickly purging inert gases, such as air and nitrogen, from the fuel electrodes during startup, leading to inefficiencies and potential residual inert gases remaining in the system.
Innovation Solution
A fuel cell system incorporating a dual-ejector setup with a controller that adjusts the usage ratio of first and second ejectors based on pressure thresholds to efficiently purge non-fuel gases by varying the mixed gas composition and flow rates, ensuring rapid and thorough removal of inert gases without the need for a hydrogen pump.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single ejector is used to supply fuel gas to the fuel cell stack, then the device complexity is reduced, but the purging efficiency of inert gases deteriorates
Solution Approach 1:
The single ejector is divided into two separate ejectors (first ejector and second ejector) that operate in parallel. Each ejector handles different aspects of the purging process, with the first ejector primarily responsible for rapid inert gas removal and the second ejector supplying additional fuel gas to ensure complete purging, thereby resolving the contradiction between device simplicity and purging efficiency.
Solution Approach 2:
The system dynamically switches between different ejector configurations based on operating conditions. During startup purging, both ejectors operate simultaneously with optimized flow rates to maximize inert gas removal. During normal operation, the system transitions to using only the first ejector, thereby adapting the system complexity to the actual operational needs and resolving the contradiction.
2Productivity
If fuel gas flow rate is increased to accelerate inert gas purging, then the purging speed improves, but the fuel gas consumption increases
Solution Approach 1:
The system optimizes the flow rate parameters of both ejectors based on the purging stage. During the initial rapid purging phase, the first ejector operates at high flow rate to quickly remove most inert gases. As purging progresses, the flow rate is dynamically adjusted downward, and the second ejector compensates to maintain effective purging while reducing overall fuel gas consumption, thus resolving the contradiction.
Solution Approach 2:
The dual ejector configuration ensures continuous effective purging action throughout the process. The first ejector maintains primary purging function while the second ejector provides supplementary fuel gas flow to prevent inert gas recirculation, ensuring uninterrupted purging efficiency without requiring excessive fuel gas flow rates at any single point, thereby resolving the contradiction between purging speed and fuel consumption.
3Reliability
If a hydrogen pump is installed to enhance inert gas circulation and purging, then the purging completeness improves, but the device complexity and cost increase
Solution Approach 1:
The invention extracts and eliminates the need for the hydrogen pump by using the dual ejector configuration to achieve the same purging completeness. The ejectors create sufficient gas flow and pressure differential to circulate and remove inert gases effectively without requiring an additional active pumping component, thereby resolving the contradiction between purging completeness and device complexity.
Solution Approach 2:
The system uses its existing fuel gas supply infrastructure (the two ejectors) to perform the circulation and purging function that would otherwise require a separate hydrogen pump. The ejectors self-regulate the gas flow to achieve complete inert gas removal, making the system self-sufficient and eliminating the need for additional components, thus resolving the contradiction.
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
The system effectively purges inert gases from the fuel electrodes in a short time, enhancing startup efficiency and reducing residual inert gas presence, even without a hydrogen pump, thereby improving fuel cell system performance and cost-effectiveness.
Implementation Method 1
uses such inverse circulation properties of an ejector, that by setting the supply amount of fuel gas at the starting moment to the range where the fuel gas flows inversely from an ejector through a circulation passage to a fuel cell
Data Source
AI summary
To provide a fuel cell system configured to, at the time of starting the fuel cell system, purge gas other than fuel gas from the fuel electrodes of a fuel cell stack in a short time. A fuel cell system comprising: a fuel cell stack, an ejector set, a fuel gas supplier, a circulation flow path, a mixed gas supply flow path, a pressure detector which detects pressure information of a fuel electrode side of the fuel cell stack, a fuel off-gas discharger which discharges the fuel off-gas, in which a concentration of the fuel gas is a predetermined concentration or less, to the outside, and a controller, wherein the ejector set includes a first ejector and a second ejector in parallel, the first ejector being an ejector which supplies first mixed gas to the fuel electrodes of the fuel cell stack, and the second ejector being an ejector which supplies second mixed gas, in which a content ratio of the circulation gas is larger than the first mixed gas, to the fuel electrodes of the fuel cell stack.