Fuel Cell Separator Variable Cross-Sectional Area
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Solution Overview
Problem
In fuel cells, the uneven wet state caused by the configuration of gas and coolant flow passages in separators leads to reduced output voltage, with the gas flow passage becoming dry downstream due to increased pressure loss and inadequate water drainage.
Innovation Solution
The fuel cell design features a separator with a gas flow passage and a coolant flow passage, where the cross-sectional area of the gas flow passage is smaller downstream and larger upstream, and vice versa for the coolant flow passage, to reduce pressure loss and improve water distribution, ensuring a uniform wet state and efficient heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the gas flow passage and coolant flow passage are configured as the front side and back side of the same separator, then the structure is simplified, but the wet state in cells becomes uneven with the gas downstream portion drying out
Solution Approach 1:
The patent applies local quality by varying the cross-sectional area of the gas flow passage at different locations. Specifically, the cross-sectional area is made smaller in the downstream region and larger in the upstream region, creating location-specific flow characteristics that compensate for pressure loss distribution and maintain uniform moisture distribution throughout the cell
Solution Approach 2:
The patent changes the geometric parameter (cross-sectional area) of the gas flow passage along the flow direction. By gradually reducing the cross-sectional area from upstream to downstream, the flow velocity and pressure distribution are optimized to prevent excessive drying in the downstream region while maintaining the simplified single-separator structure
2Device complexity
If the cross-sectional area of the gas flow passage is constant, then the structure is simple, but pressure loss increases and moisture distribution becomes uneven
Solution Approach 1:
The patent applies parameter changes by making the cross-sectional area of the gas flow passage variable rather than constant. The cross-sectional area is designed to be smaller in the downstream region and larger in the upstream region, which optimizes the pressure gradient distribution and reduces overall pressure loss while improving moisture distribution uniformity
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 design enhances the wet state and increases output voltage by reducing pressure loss and preventing flooding and drying, thereby improving the overall performance of the fuel cell.
Implementation Method 1
the cross-sectional area of the concave portion constituting the gas flow passage of the separator is set such that it becomes relatively smaller on a gas downstream side than on a gas upstream side
Implementation Method 2
Cooling water is supplied to a convex portion of the press separator, that is the concave portion on the back surface, to thereby cool an MEA
Implementation Method 3
The hydrogen-containing gas is supplied to the anode-side electrode through a fuel gas flow passage, and is dissociated into electrons and hydrogen ions by the action of a catalyst of the electrode
Implementation Method 4
the hydrogen ions pass through the electrolyte membrane and reach the cathode-side electrode
Implementation Method 5
where the hydrogen ions bond to oxygen and the electrons passing through the external circuit, to thereby produce reaction water
Data Source
AI summary
Provided is a fuel cell, the output voltage of which is improved by making a membrane moist state uniform. An anode-side gas diffusion layer and a cathode-side gas diffusion layer are joined to a membrane electrode assembly, and a separator is joined to the anode-side gas diffusion layer. The separator has a recess portion and a protrusion portion formed to constitute a gas flow path and a refrigerant flow path, respectively. The cross-sectional area of the recess portion is made relatively small at the downstream side in comparison with that at the upstream side, and the cross-sectional area of the protrusion portion is made relatively large at the downstream side in comparison with that at the upstream side, thereby improving the moist state.