| To solve the increasingly serious problem on air pollution and fossil energy depletion,and in order to prevent the low combustion efficiency of fuel machine because of the low oxygen and high humidity,promoting electric engineering vehicles is a developing direction of engineering vehicles.As the energy source of electric vehicles,the power battery pack is one of the most critical parts of electric vehicles.In order to meet the requirements of the engineering vehicle for working voltage,discharge current and endurance,the battery pack of the electric engineering vehicle usually requires a large number of monomer batteries.And in order to avoid differences and prolong the sevice life of the battery pack,we should use the same kind of monomer battery,and ensure that the monomer batteries work under similar environmental temperature.In addition,as a power battery,the lithium-iron phosphate battery pack has the advantages of higher energy,higher working voltage and longer life expectancy.It is one of the best choices for power monomer batteries.But its thermal performance is not stable,discharge temperature can’t be greater than 60 ℃,and the best discharge temperature is below 35 ℃.However,in some poor working environment,the temperature is easy to rise to greater than 60 ℃.We need cooling system for batteries.The main contents of this paper are as follows:1.Design the battery pack and choose the monomer battery by calculating the working voltage,current,capacity.2.Establish an air cooling system for thermodynamic calculation,and calculate the heat and heat transfer.3.Through Icepak simulation and theoretical analysis,the optimization effect of the structure optimization and the increase of filter plate on the cooling effect of air cooling system is proved.4.Determine the optimization effect of the filter plate on the heat dissipation of the battery pack,and determine the influence of the opening rate on it.In order to let the wind flow more to the area with poor heat dissipation effect,the filter plate should be changed to open hole rate,high battery temperature,and increased porosity in the area with poor heat dissipation.Low battery temperature and low porosity in the area.After this design,the maximum temperature,average temperature and standard deviation were 34.23℃,27.76℃and 1.911℃.,respectively,compared with the distance between the optimized filter plate decreased 14.82 ℃,2.38 ℃,1.060 ℃;The filter plate(opening rate =0.1)was reduced by2.64℃,0.35℃ and 0.102℃.5.On the basis of verifying that the cooling system can meet the heat dissipation under high power condition,the paper puts forward that using fuzzy PID system to control the wind speed in different working conditions.When the power is 30 kW,the wind speed is10m/s,and when the power is 10 kW,2m/s wind speed is used.And the wind speed is adjusted according to the temperature feedback by system itself.The results show that the optimization of filter plate with variable opening rate is even more effective than structural optimization.It provides useful reference for the cooling of battery pack. |
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