Fuel Cell Ejector Set for Condensed Water Suppression
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Solution Overview
Problem
Fuel cell systems face challenges in maintaining power generation performance due to the generation and flow of condensed water into the fuel cell stack when low-temperature fuel gas is supplied, leading to decreased efficiency.
Innovation Solution
A fuel cell system with an ejector set comprising two parallel ejectors, where the controller adjusts the usage ratio of each ejector based on the fuel gas temperature, switching to a lower circulation gas ratio when temperatures are low to minimize condensed water generation and flow into the stack.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If heat exchange between fuel gas and cooling water is used to increase fuel gas temperature, then fuel gas temperature can be increased, but the temperature increase is insufficient when cooling water temperature is not sufficiently high
Solution Approach 1:
An ejector is introduced as an intermediary device to mix high-temperature circulation gas with low-temperature fuel gas, achieving temperature increase without direct thermal contact between fuel gas and cooling water. The circulation gas acts as a thermal mediator, transferring heat to the fuel gas through mixing rather than conventional heat exchange
Solution Approach 2:
The system changes the temperature parameter of fuel gas by mixing it with circulation gas at different temperatures. The ejector creates a mixed gas with an intermediate temperature that is higher than the original fuel gas temperature, effectively adjusting the temperature parameter without relying on cooling water temperature
2Productivity
If fuel cell stack operates in high load condition to rapidly consume high-pressure fuel gas, then fuel consumption rate increases, but fuel gas temperature remarkably decreases due to adiabatic expansion
Solution Approach 1:
The system performs preliminary heating of fuel gas by mixing it with pre-heated circulation gas before the fuel gas enters the fuel cell stack. This preliminary action prevents the fuel gas from undergoing severe adiabatic cooling during high-load operation, maintaining temperature above the dew point
Solution Approach 2:
The circulation gas, which has been heated by passing through the fuel cell stack, is fed back to the ejector to mix with incoming fuel gas. This feedback mechanism continuously provides thermal energy to the fuel gas, compensating for temperature drops during high-load operation
3Quantity of substance
If low-temperature fuel gas is supplied to ejector and mixes with circulation gas containing moisture, then condensed water is generated in ejector and outlet port, but condensed water may enter fuel cell stack and decrease power generation performance
Solution Approach 1:
The ejector mixes fuel gas with circulation gas in controlled ratios to achieve a mixed gas temperature that remains above the dew point. By adjusting the mixing ratio parameter, the system prevents condensation while still utilizing circulation gas for thermal management and fuel efficiency
Solution Approach 2:
The system converts the potentially harmful cold fuel gas into a beneficial component by mixing it with warm circulation gas in the ejector. The low-temperature fuel gas, when mixed properly, contributes to overall system efficiency while the mixed gas temperature is maintained to prevent condensation, turning a harmful condition into a beneficial mixing process
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 solution effectively suppresses the generation and flow of condensed water into the fuel cell stack, thereby maintaining power generation performance even at low fuel gas temperatures.
Implementation Method 1
an ejector set which supplies mixed gas containing the fuel gas and the circulation gas to the fuel electrodes of the fuel cell stack
Implementation Method 2
A fuel cell is a power generation device that generates electrical energy by electrochemical reaction between hydrogen (H2), which serves as fuel gas, and oxygen (O2), which serves as oxidant gas
Implementation Method 3
a membrane electrode assembly (MEA) and, as needed, two separators sandwiching the membrane electrode assembly... a solid polymer electrolyte membrane having proton (H+) conductivity
Implementation Method 4
the hydrogen supplied from the flow path and the gas diffusion layer is protonated by the catalytic activity of the catalyst layer
Implementation Method 5
fuel gas released from the fuel gas supplier of the system, such as a fuel tank, is cooled down by adiabatic expansion, and the temperature of the fuel gas is remarkably decreased
Data Source
AI summary
To suppress the generation of condensed water and suppress the flow of the condensed water into a fuel cell stack. A fuel cell system comprising: a fuel cell stack, an elector set, a fuel gas supplier which supplies fuel gas to the ejector set, a circulation flow path, a mixed gas supply flow path, a temperature detector which detects a temperature of the fuel gas, and a controller, wherein the ejector set includes at least two ejectors in parallel, which are a first ejector that supplies first mixed gas to the fuel electrodes of the fuel cell stack, and a second ejector that supplies second mixed gas, in which a content ratio of the circulation gas is smaller than the first mixed gas, to the fuel electrodes of the fuel cell stack.