Research On Thermal Management System Of High-power Proton Exchange Membrane Fuel Cell

To cope with environmental and energy problems,China has carried out extensive research on new energy and its applications under the guidance of "carbon peaking" and "carbon neutrality".Proton Exchange Membrane Fuel Cell（PEMFC）is a type of fuel cell that uses hydrogen to generate electricity.It has advantages like high energy conversion efficiency,zero pollution and no emissions,and high specific power.It is widely used in transportation,energy storage,power backup and so on.PEMFC is developing towards higher power driven by many factors such as policy and demand at present.PEMFC Liquid-cooled thermal management system（TMS）is also widely used in application.One-dimensional numerical simulation and experimental verification are used to analyze the heat generation and temperature characteristics of PEMFC,and a liquid-cooled TMS is designed according to its heat dissipation requirements in this research.Taking the temperature of coolant inside PEMFC stack and parasite loss as the evaluation index,the effects of different TMS control strategies are discussed.In the process of analyzing the heat generation and temperature characteristics of PEMFC,the output voltage of PEMFC is analyzed firstly based on the electrochemical reaction principle of PEMFC,and a function of the output voltage with the current density as the independent variable is established.The specific model of PEMFC output voltage is obtained from the V-I-P test data of PEMFC stack used in the research.On this basis,the output power model and heat power model of PEMFC are established according to the principle of energy conservation,and the stack temperature model is established according to the physical properties of the PEMFC stack.After that,the PEMFC is tested in a PEMFC test system,and the test conditions are used to simulate with the Simulink models of the PEMFC’s output voltage,output power,heat power,and stack temperature.By comparing the simulation and test results,the maximum error of output voltage is 6.124%,the maximum error（absolute value）of output power is 8.58%,and the maximum error of stack temperature is 4.59%.In order to meet the heat dissipation requirements of the PEMFC,a liquid-cooled TMS based on the heat power of the PEMFC under rated power is designed accordingly.The design process includes system architecture design,selection of cooling medium and key components including radiator,thermostat,pump and fan.The heat transfer performance of the selected radiator under the design condition is verified using three-dimensional simulation.It is shown that the error between the simulation value of the radiator outlet air temperature and the design value was 8.24%.According to the designed TMS,a simulation model using CRUISE M is established,a test rig is built and preliminary control strategy is devised.The results of experiment and simulation under the same conditions are compared,it is indicated that the simulation model of the PEMFC TMS has an error of 3.12% for the temperature of the cooling liquid at the stack inlet and 1.81% for the temperature of the cooling liquid at the outlet of the stack under the steady-state operating conditions of the stack.In order to formulate a reasonable control strategy for the designed PEMFC TMS,it is concluded that PEMFC temperature is mainly affected by fan speed,and the temperature uniformity is affected by pump speed through simulation analysis.In order to control the PEMFC temperature characteristic,the coolant temperature and coolant pressure are selected as the control basis respectively,and PID controller and fuzzy logic controller are selected as control method.According to the control bases and control methods above,four different control strategies are devised.Then simulations of different control strategy schemes are carried out,and results obtained are compared.It is concluded that the control strategy that adjusting pump speed according to cooling liquid pressure at stack inlet and adjusting fan speed according to temperature difference using fuzzy logic controller is more beneficial to the performance and safety of the PEMFC stack and more economical.A favorable reference for the development of matching and control of the liquid-cooled TMS of high-power PEMFC in practical application is provided in this research.