| With the energy-saving and environmental-protecting ideas deeply rooted in people's minds,electric vehicles will become the mainstream transportation in the future.As the mainstream power source for battery electric vehicles,power lithium batteries have the advantages such as environmental protection,low self-discharge rate,and long cycle life,etc.Lithium-powered batteries are the core components of the vehicle.They generate a lot of heat due to their own characteristics during charge and discharge.If these heats cannot be quickly emitted,the temperature of the lithium battery pack will rise sharply,which will seriously affect the performance and cycle life of the battery pack.Even worse,it may cause thermal runaway problems and the vehicle will burn,which will endanger the safety of vehicles and people.Therefore,it is necessary to perform thermal management of the lithium battery pack.In this paper,with the lithium iron phosphate monomer(Li Fe PO4)as the research object,solid three-dimensional model and heat simulation model are established,and the temperature distribution of the monomer is simulated by the simulation software.Based on the analysis result,the cooling structure and the box structure of the lithium iron phosphate power battery module are designed.Passive air cooling and liquid cooling are used to analyze the heat dissipation of the battery module through CFD software to verify whether the simulation results meet the battery module design goals.The main contents of this paper's research are as follows:(1)The structure of rectangular Li Fe PO4 battery and the movement law of Li+ inside the battery during charge and discharge are introduced.And the heat source and heat transfer characteristics of Li Fe PO4 battery are analyzed.The four basic equations for the computational fluid and the general steps for solving the equation are described.(2)Rationally simplifying the single structure of Li Fe PO4 battery,the heat rate model and three-dimensional model are established.The parameters such as the density of the battery cell,the thermal conductivity in the space direction,the specific heat capacity,and the function expression of the heat generation rate are determined.The fluent software is used to analyze the temperature rise cloud diagrams after the battery cells are discharged at different rates under ambient temperature and natural convection conditions.A battery cell model verification experiment is set up to demonstrate the reliability of the thermal model.(3)With the power and cruising range of battery electric vehicles as the constraint,an entire vehicle model is built in ADVISOR.The vehicle model is simulated under different operating conditions to obtain the curve of relevant parameters of the vehicle and Li Fe PO4 battery modules.At the same time,in order to meet the maximum power of the vehicle as the goal,the relationship between the heat generation rate and the time(q-t)of the battery module under extreme conditions is obtained.(4)The structure of the cooling pipe and the box shape is designed,and the geometric model of the Li Fe PO4 battery module is established.And the thermal management goals of the Li Fe PO4 module are set and the stress intensity of the pipeline is checked.Under compound cooling conditions,the temperature rise of the Li Fe PO4 module is analyzed.The results meet the design goals of the maximum temperature and the monomer temperature difference of the battery pack. |
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