Design And Performance Research Of High Temperature Proton Exchange Membrane Fuel Cell With Fractal Tree-like Flow Field

The proton exchange membrane fuel cell which using hydrogen as fuel has many characteristics,such as no pollution,high conversion rate,high applicability,has been widely used in the application of fixed power supply,mobile devices and transportation.However,problems of catalyst poisoning and complex water thermal management has hinder its marketization duo to the working temperature below 80 ℃.High temperature proton exchange membrane fuel cell will increase working temperature to 100℃ to 200 ℃,not only solve this problems,but also improve the energy conversion efficiency of the fuel cell.At the same time,it put forward new requirements in the design of fuel cell flow field and material properties.Fractal tree-like structure is a kind of optimized natural network structure,in this dissertation,as the change of the high temperature proton exchange membrane fuel cell flow field design concerns,we design a flow field which based on fractal tree-like structure which makes the fuel cell supply adequate evenly,improve the reaction gas transport properties and fuel cell performance.In this dissertation,main works are as follows:(1)Made a briefly introduce of the design thought of Murray’s law and the tree fractal flow field,calculate the size of flow field according to the Murray’s law and it’s formula,design a new tree fractal structure of flow field with combination of parallel flow field.(2)A steady-state phase and three-dimensional model of high temperature proton exchange membrane fuel cell which based on fractal tree-like structure and traditional parallel flow field has been established,and using computational fluid dynamics numerical calculation method to simulate the polarization curve of the fuel cell,distribution of gas concentration,current density distribution,pressure drop values and distribution.Simulation results show that the design of new type compare to the traditional parallel flow field,the maximum output power density of fuel cell increased by 23.9%,at the same time,has more uniform distribution of gas distribution and the pressure drop.(3)Based on the characteristics of new materials,a high temperature proton exchange membrane fuel cell which fractal tree-like structure flow field has been assembled,and a platform design for fuel cell performance test has been established.The results of fuel cell performance test and numerical calculation show that polarization curve and power density curve has same general trend,and the deviation is very small,has been verified the design of the tree fractal flow field has excellent mass transportation.The flow field structure of fuel cell decided the reaction gas transmission and distribution,has great influence to the fuel cell performance.This dissertation designed a new fractal tree-like flow field structure to reduce the flow resistance and uniform distribution of reaction gas,and improved the fuel cell internal transport properties of reaction gas and the overall performance of the fuel cell,have a significant reference on the design of high temperature proton exchange membrane fuel cell new flow field.