Fuel Cell System Low Temperature Warm-Up Control
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Solution Overview
Problem
Combining existing technologies for cathode-off gas circulation in fuel cells leads to a difficulty in quickly decreasing the current/voltage characteristic, especially during low-efficiency power generation, as the oxygen concentration in the circulation system does not decrease sufficiently, affecting the fuel cell's performance and warm-up efficiency.
Innovation Solution
A fuel cell system with a stoichiometry decreasing process unit that reduces the oxidant gas supply, accompanied by an oxidant-off gas circulating process unit that reintroduces oxidant-off gases into the supply flow channel, maintaining gas flow volume and preventing flooding, thereby quickly decreasing the current/voltage characteristic and promoting stable power generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the stoichiometric amount of oxidant gases is reduced to perform low-efficiency power generation for warm-up, then the warm-up efficiency is improved, but the current/voltage characteristic cannot be quickly decreased because the oxygen concentration in the circulation system does not decrease
Solution Approach 1:
The system performs preliminary action by reducing the stoichiometric amount of oxidant gases before starting the circulation of oxidant-off gases. This preliminary reduction in oxygen supply prepares the system for rapid IV characteristic decrease once circulation begins, resolving the contradiction by sequencing actions to achieve both warm-up efficiency and quick characteristic decrease.
Solution Approach 2:
The system maintains continuous gas flow through the circulation of oxidant-off gases back to the oxidant gas supply. This continuous circulation ensures that the reduced oxygen concentration is maintained throughout the system, allowing the IV characteristic to decrease quickly while sustaining the low-efficiency power generation mode for effective warm-up.
2Reliability
If oxidant-off gases are circulated to discharge produced water in the cathode, then the power generation stability is improved, but the oxygen concentration in the circulation system does not decrease, making it difficult to quickly decrease the current/voltage characteristic
Solution Approach 1:
The system changes the parameter of oxidant gas supply by reducing the stoichiometric amount before initiating circulation. This parameter change ensures that even though oxidant-off gases are continuously circulated for water discharge and stability, the oxygen concentration remains low enough to enable quick IV characteristic decrease.
3Speed
If the stoichiometric amount of oxidant gases is reduced, then the current/voltage characteristic decreases, but the gas flow volume decreases, causing flooding in the cathode
Solution Approach 1:
The system merges the oxidant-off gas discharge flow channel with the oxidant gas supply flow channel through the oxidant-off gas introducing flow channel. This merging allows the circulated gases to maintain sufficient flow volume for preventing cathode flooding while the reduced stoichiometric amount ensures the IV characteristic decreases quickly.
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 decreases the current/voltage characteristic and facilitates rapid warm-up by ensuring sufficient gas circulation and water discharge, enhancing the fuel cell's power generation stability and efficiency.
Implementation Method 1
a fuel cell which comprises an anode and a cathode and which generates power when a fuel gas and an oxidant gas are supplied to the anode and the cathode, respectively
Data Source
AI summary
The present invention provides a fuel cell system that can quickly decrease a current/voltage characteristic. A fuel cell system includes an introduction piping which connects a discharging piping and a supply piping in communication with each other, and which introduces part of oxidant-off gas in the supply piping, and a circulation on-off valve provided in the introduction piping. The fuel cell system decreases the supply amount of air by an air compressor when a fuel cell is activated at a low temperature to decrease the air-stoichiometry of the fuel cell, and opens the circulation on-off valve to introduce the oxidant-off gas in the supply piping through the introduction piping, thereby causing the oxidant-off gas to circulate.