Fuel Cell Idling Stop Control via Oxidant Flow Rate Adjustment
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Solution Overview
Problem
Fuel cell systems face challenges during idling stop conditions, including electrolyte membrane degradation, cell voltage decline, and noise vibration (NV) performance deterioration due to high oxidant gas flow rates, especially in low-pressure environments, where existing technologies require discharge resistors and are inefficient in transitioning to idling stop without oxidant gas supply.
Innovation Solution
A fuel cell system with an idling stop control method that supplies oxidant gas at a lower flow rate than during idling power generation, producing lower current and ensuring oxidant off-gas for dilution, while limiting air pump operation in low-pressure environments to maintain NV performance, and includes mechanisms to recover cell voltage by increasing oxidant gas flow rate when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If oxidant gas supply is stopped during idling stop to improve fuel efficiency, then fuel efficiency is improved, but electrolyte membrane degradation occurs due to high potential and cross-leakage reactions
Solution Approach 1:
The system determines whether to execute idling stop in advance by checking if the air pump is operating in a low-pressure environment (e.g., high altitude). If low-pressure conditions are detected, the system prevents idling stop execution beforehand, avoiding the subsequent membrane degradation problem while maintaining fuel efficiency in normal conditions
Solution Approach 2:
The system continuously monitors atmospheric pressure and adjusts idling stop execution decisions based on real-time environmental conditions. When pressure drops below a threshold indicating low-pressure environment, feedback control prevents idling stop, thereby protecting the membrane while optimizing fuel efficiency in normal pressure conditions
2Reliability
If oxidant gas of high flow rate is supplied during idling stop to prevent membrane degradation, then membrane durability is improved, but NV performance deteriorates due to noise and vibration
Solution Approach 1:
The system changes the operating parameters of the air pump based on environmental pressure conditions. In low-pressure environments, the air pump operates at restricted speeds to reduce NV noise, while still supplying sufficient oxidant gas to prevent membrane degradation through cross-leakage reactions
3Loss of energy
If idling stop is executed without checking environmental pressure to improve fuel efficiency, then fuel efficiency is improved, but cell voltage declines due to flooding phenomenon in low-pressure environments
Solution Approach 1:
The system performs preliminary detection of atmospheric pressure conditions before executing idling stop. When low-pressure environment is detected, the system prevents idling stop execution, thereby avoiding cell voltage decline caused by flooding phenomenon while maintaining fuel efficiency in normal pressure conditions
Solution Approach 2:
The system uses real-time atmospheric pressure feedback to control idling stop execution. When pressure indicates low-pressure environment, feedback control prevents idling stop, avoiding voltage instability from flooding while optimizing fuel efficiency when pressure conditions are normal
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 prevents electrolyte membrane degradation, maintains stable cell voltage, and improves fuel efficiency by quickly transitioning to idling stop without the need for discharge resistors, while suppressing NV performance deterioration in low-pressure environments.
Implementation Method 1
the fuel cell generates power by allowing reactant gases to undergo an electrochemical reaction
Implementation Method 2
the fuel off-gas discharged from the fuel cell is introduced into this diluter, and temporarily stays inside the diluter, and then is diluted and discharged. Oxidant off-gas discharged from the fuel cell is used to dilute the fuel off-gas
Data Source
AI summary
A fuel cell system that can quickly transition to idling stop and can suppress degradation of the electrolyte membrane and decline in cell voltage during idling stop, without requiring a discharge resistor to be provided, and a control method thereof are provided. A fuel cell system (1) includes a fuel cell (10) configured by layering a plurality of fuel cell cells that generate power by reactant gas being supplied thereto, and a supply device 20 that supplies reactant gas to the fuel cell (10), in which idling stop control is initiated to supply air of a lower flow rate than during idling power generation to the fuel cell (10), while producing lower current than during idling power generation from the fuel cell (10), in a case of a predetermined condition being established during idling power generation.