Variable Cross-Section Manifold for Fuel Cell Flow Uniformity
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Solution Overview
Problem
In fuel cell systems, the dispersion of wet states among cells in a stack lamination direction is exacerbated by pressure loss in manifolds, leading to uneven moisture distribution, flow rate differences, and temperature variations, which can decrease cell voltage and output.
Innovation Solution
A fuel cell system with detection means to identify wet state dispersion and control means to adjust the flow rate of a cooling medium, as well as gas flow rates and pressures, to equalize humidity across cells, thereby suppressing wet state dispersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If the manifold size is restricted to meet mounting requirements on mobile objects, then the size and weight are reduced, but the pressure loss increases and distribution uniformity deteriorates
Solution Approach 1:
The patent applies local quality by making the manifold cross-sectional area variable along its length. Specifically, the cross-sectional area is increased at locations where pressure loss is greater (typically toward the outlet end) to compensate for the cumulative pressure drop, thereby maintaining more uniform flow distribution to each cell despite the overall compact size.
2Manufacturing precision
If the manifold cross-sectional area is increased to improve flow distribution, then the distribution uniformity improves, but the moisture discharge capability deteriorates
Solution Approach 1:
The patent applies local quality by making the manifold cross-sectional area variable along its length. Specifically, the cross-sectional area is increased at locations where pressure loss is greater (typically toward the outlet end) to compensate for the cumulative pressure drop, thereby maintaining more uniform flow distribution to each cell despite the overall compact size.
Solution Approach 2:
The patent introduces grooves as intermediary structures on the inner surface of the manifold. These grooves facilitate moisture discharge by providing dedicated pathways for condensate to flow back toward the inlet, preventing moisture accumulation while maintaining the cross-sectional area needed for uniform flow distribution.
3Manufacturing precision
If pressure loss in the manifold is reduced to improve flow distribution, then the distribution uniformity improves, but the manifold size increases
Solution Approach 1:
The patent applies local quality by making the manifold cross-sectional area variable along its length. Specifically, the cross-sectional area is increased at locations where pressure loss is greater (typically toward the outlet end) to compensate for the cumulative pressure drop, thereby maintaining more uniform flow distribution to each cell despite the overall compact size.
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 reduces wet state dispersion, maintaining optimal fuel cell performance by ensuring uniform moisture distribution and flow rates, thereby preventing voltage drops and output limitations.
Implementation Method 1
a flow rate of a cooling medium for cooling the unit cells
Implementation Method 2
a flow rate of a cooling medium for cooling the unit cells
Implementation Method 3
a fuel cell that generates electricity through an electrochemical reaction between a fuel gas and an oxidizing gas
Data Source
AI summary
An ECU estimates a dispersion among wet states of cells arranged in a lamination direction of a fuel cell. When it is determined that the dispersion among the wet states is equal to or exceed a threshold, the ECU controls a flow rate of a coolant, flow rates of gases, and pressures of gases to suppress the dispersion among the wet states below the threshold. The ECU controls the flow rate of the coolant with higher priority than the other parameters.