Fuel Cell Hydrogen Recirculation Ejector
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Solution Overview
Problem
Conventional fuel cell systems with fuel recirculation types face challenges in efficiently recirculating hydrogen-containing off-gas at low flow rates, leading to system complexity and reduced compactness due to the need for additional control mechanisms.
Innovation Solution
A fuel cell system with a flow rate determination unit and a gas feeding pressure varying mechanism that adjusts the pressure of hydrogen-containing gas to ensure effective recirculation regardless of flow rate changes, using a pressure regulating valve and an ejector or hydrogen recirculation blower to manage the recirculation process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fuel pump is installed to recirculate hydrogen-containing off-gas at low flow rates, then recirculation effectiveness is improved, but system complexity increases
Solution Approach 1:
The ejector is designed to automatically recirculate hydrogen-containing off-gas using the kinetic energy of the incoming hydrogen gas flow itself, without requiring an external fuel pump. The system uses its own operating fluid (hydrogen gas) to create the suction effect through the ejector nozzle, achieving self-service recirculation that eliminates additional active components and simplifies the system
Solution Approach 2:
The ejector utilizes pneumatic principles where high-velocity hydrogen gas flow through the nozzle creates a pressure differential (Bernoulli effect) that draws in and mixes with the hydrogen-containing off-gas. This pneumatic recirculation mechanism replaces mechanical pumping, reducing system complexity while maintaining recirculation effectiveness across varying flow rates
2Use of energy by moving object
If the flow rate of hydrogen gas is reduced, then energy consumption is decreased, but recirculation effectiveness deteriorates
Solution Approach 1:
The ejector design dynamically adapts to varying hydrogen gas flow rates. The nozzle geometry and diffuser angle are optimized to maintain effective recirculation across a range of operating conditions. As the hydrogen gas flow rate changes, the ejector automatically adjusts its suction capability, ensuring continuous effective recirculation without requiring active control mechanisms
Solution Approach 2:
The system utilizes parameter changes in the hydrogen gas flow (velocity, pressure) to maintain recirculation effectiveness. By designing the ejector with specific geometric parameters (nozzle diameter, diffuser angle, mixing chamber dimensions), the system maintains optimal performance across varying flow rates, allowing energy consumption to be reduced while preserving recirculation effectiveness
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 simplifies the system, enabling effective recirculation of hydrogen-containing off-gas across varying flow rates and achieving compactness by varying the anode pressure to maintain stable power generation and improve fuel economy.
Implementation Method 1
an ejector to inhale or taking in the above hydrogen-containing off-gas by making use of a negative pressure generated by the flow of the above hydrogen gas
Implementation Method 2
a cell unit that generates power/electricity by separating hydrogen-containing gas and oxygen-containing gas from each other and in flowing contact with each other
Data Source
Figure 1(A)~1(B)
Figure 2
Figure 3(A)~3(B)
AI summary
The fuel cell system is simplified and made more compact in addition to causing the favorable recirculation of hydrogen-containing off-gas regardless of the increase or decrease in the flow rate of hydrogen-containing gas. The fuel cell system is provided with: a cell unit (11) that generates electricity by means of separating hydrogen-containing gas and oxygen-containing gas from each other while placing in flow contact to each other; and a recirculation mechanism for recirculating to the cell unit (11) hydrogen-containing off-gas discharged from the cell unit (11). The fuel cell system has a flow rate determination unit(C1) that determines whether or not the hydrogen-containing gas fed to the cell unit (11) is less than a predetermined flow rate; and a gas feeding pressure varying mechanism (C2) that cause the pressure of the hydrogen-containing gas to vary to increase and decrease when it is determined that the hydrogen-containing gas fed to the cell unit is less than the predetermined flow quantity.