Fuel Cell Separator Reactant Gas Control for Flooding Prevention
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Solution Overview
Problem
Conventional proton exchange membrane fuel cells (PEMFCs) face issues with flooding and concentration polarization due to excessive reactant gas supply, leading to inefficient operation and increased power consumption, particularly under varying load conditions.
Innovation Solution
A fuel cell separator design with alternately formed reactant gas inlet and outlet through holes and meandering passages to control reactant gas flow, along with end plates equipped with valves to manage gas flow based on operation conditions, ensuring optimal gas supply without excessive gas consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional fuel cell separators supply reactant gas through simple groove-shaped passages, then the structure is simple and easy to manufacture, but flooding and concentration polarization occur due to excessive gas supply and improper flow distribution
Solution Approach 1:
The separator is divided into multiple functional regions: reactant gas inlet regions, outlet regions, and intermediate regions with through-holes. This segmentation allows different parts of the separator to perform different functions - supplying gas at inlet, removing liquid water at intermediate regions, and collecting gas at outlet regions - thereby preventing flooding and concentration polarization while maintaining manufacturing simplicity
Solution Approach 2:
Through-holes are introduced as intermediary structures connecting the inlet and outlet regions. These through-holes serve as intermediate pathways that allow reactant gas to flow through the separator thickness, providing additional gas supply paths and preventing excessive pressure buildup that would cause flooding, while also allowing liquid water to be removed effectively
2Productivity
If reactant gas supply is increased to prevent concentration polarization, then gas supply to electrodes is improved, but flooding occurs and power consumption increases
Solution Approach 1:
Different regions of the separator are designed with different properties: inlet regions have gas supply passages, intermediate regions have through-holes for both gas flow and liquid water removal, and outlet regions have gas collection passages. This local differentiation allows optimal gas distribution without excessive supply, preventing both concentration polarization and flooding while reducing unnecessary power consumption
3Ease of manufacture
If simple groove-shaped passages are used in separators, then manufacturing is easier, but proper reactant gas distribution and water removal cannot be achieved
Solution Approach 1:
The separator is segmented into inlet regions with gas supply passages, intermediate regions with through-holes, and outlet regions with gas collection passages. This segmentation can be achieved through straightforward molding processes, maintaining ease of manufacture while dramatically improving gas distribution and water removal efficiency
Solution Approach 2:
The design transitions from two-dimensional groove-shaped passages on the separator surface to three-dimensional flow paths that extend through the separator thickness via through-holes. This dimensional change enables effective water removal and gas distribution without complicating the manufacturing process, as the through-holes can be formed through simple vertical molding
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 prevents flooding and concentration polarization by adjusting reactant gas supply according to operation conditions, maintaining efficient operation without pressure loss and reactant gas utilization rate deterioration.
Implementation Method 1
A PEMFC uses a proton exchange membrane having a hydrogen ion exchange property as an electrolyte membrane
Implementation Method 2
The PEMFC generates electricity and heat through an electrochemical reaction between a fuel gas containing hydrogen and air containing oxygen
Implementation Method 3
a diffusion layer formed on an outer surface of the catalyst layer and having breathable and electron conduction properties
Implementation Method 4
The PEMFC includes a cooling unit along which a coolant flows and which is installed for one through three unit cells to dissipate heat generated by the operation thereof
Data Source
AI summary
A fuel cell separator, a fuel cell stack having the fuel cell separator, and a reactant gas control method of the fuel cell stack are provided. That is, even when the fuel cell stack operates under the low load operation condition, a reactant gas is supplied to the reactant gas passages of the fuel cell separator, and thus, the length of the passage can be shortened by 50% as compared with the prior art having only one reactant gas passage. Therefore, the reactant gas can be effectively supplied without experiencing pressure loss. Further, in the high load operation of the fuel cell stack, the reactant gas is introduced into the first reactant gas passage of the fuel cell separator and utilized in half of the whole electrode area. Subsequently, the reactant gas is introduced into the second reactant gas passage and utilized in the remaining half of the electrode area. The flow rate of the reactant gas flowing along the passage channels is increased by two times, even when the reactant gas utilizing rate is identical as compared with the reactant gas flow in the low load operation. As a result, the moisture existing in the passage channels can be more effectively discharged and the flooding phenomenon occurring in the high load operation can be prevented. By controlling the reactant gas supply in accordance with an operation condition of the fuel cell stack without experiencing pressure loss and deterioration of the utilizing rate, the flooding phenomenon and concentration polarization phenomenon that occur in the fuel cell stack can be prevented.