| After the country puts forward development goals such as low-carbonization,informatization,and intelligence,the continuous optimization of power batteries,drive motors,and electronic control technologies will help the low-carbon process of the automotive industry.New energy vehicles have become an inevitable trend in future automotive development.As the core component of electric vehicles,power batteries have become the focus of attention.Among them,lithium-ion batteries have the advantages of high voltage,high energy density,and long cycle life,and have become the power source of electric vehicles.However,the performance and life of lithium-ion batteries are greatly affected by temperature.Too high or low temperature will affect the performance and life of the battery.Therefore,this article aims to improve the performance and life of the battery system,and the following work is carried out:(1)Select a certain type of soft pack battery as the research object,and determine the battery grouping method and the number of batteries based on the performance parameters of a certain vehicle.Establish the battery cell heat generation model,calculate the battery’s thermal physical parameters,conduct the battery internal resistance test experiment,and simulate the temperature rise simulation of the battery cell at different discharge rates through the CFD simulation software Fluent.And through the battery temperature rise experiment to compare with the simulation results,verify the correctness of the battery cell thermal model.Then the natural temperature rise simulation of the battery pack is carried out.The simulation results show that without the intervention of the cooling system,the temperature and temperature difference of the battery exceed the optimal operating temperature range,which seriously affects the performance and life of the battery system.(2)Four new structures of cooling pipes are designed,and CFD simulation method is used to simulate and analyze the four cooling pipes.Considering factors such as temperature rise,temperature balance and pressure drop,structure four is selected as the research object of this article.Based on the fourth structure of the cooling pipe,four cross-sectional sizes are designed,and simulation analysis is carried out,and it is concluded that the cross-sectional size 2 is the better heat dissipation result.(3)Based on the heat dissipation structure 4 of the cross-sectional size 2 scheme,four kinds of cooling liquids with lower freezing points are used as the research object for simulation analysis,and it is concluded that the 50% glycol aqueous solution has the best heat dissipation performance.The influence of the flow rate on the temperature balance of the battery is studied.As the flow rate of the coolant increases,the balance of the battery is better.When the flow rate is 4L/min,the temperature of the battery can be controlled within the optimal operating temperature range.Fifteen combined charging rate test programs were designed,and the optimal combined charging test program was determined based on the two factors of maximum temperature difference and charging time.In the simulation analysis of ambient temperature conditions,it is concluded that the battery liquid cooling system needs to force the cooling liquid to dissipate heat at an ambient temperature of 35°C.(4)Select the type of executive components,propose a control strategy based on PID algorithm,build a one-dimensional liquid cooling structure and an air conditioning refrigeration circuit,and design the A and B cycle conditions to obtain a good cooling performance of the refrigeration circuit.And set up a heating system to simulate heating in three different low-temperature environments.Finally,build the vehicle power model and integrate it into the battery liquid cooling system.The four vehicle cycle conditions are simulated and analyzed at an ambient temperature of 35°C,and the battery temperature is controlled at the target temperature under the action of the control system. |
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