| The crawler operation platform had good stability and obstacle surmounting ability.It can complete many operations such as transfer,picking,pruning and so on in orchards with poor road conditions in Hilly and mountainous areas.Compared with the internal combustion engine crawler operating platform,the pure electric crawler operating platform had no exhaust emissions during use,and had a broader application prospect under the background of energy and environmental issues.However,there are too many batteries in the battery pack of the pure electric crawler platform,which will make the overall weight of the platform too large and difficult to transfer.The small number of batteries in the battery pack will lead to the small capacity of the battery pack.When the operating platform is in high temperature,climbing,heavy load and other working conditions,the battery pack may have insufficient heat dissipation.Therefore,studying the heat dissipation demand of the battery pack of the tracked platform under different working conditions and designing a reasonable heat dissipation system are the key to the wide application of the electric tracked platform in Hilly and mountainous areas.In this paper,a pure electric crawler type operating platform power battery pack suitable for orchard production in Hilly and mountainous areas independently developed by the research group is taken as the research object.Through theoretical analysis,experimental research and CFD simulation,different ambient temperatures(normal temperature 25 ℃ and high temperature 35 ℃),different road conditions(flat road,slope of 14.6 °)and According to the heat dissipation requirements of the battery pack under20 transfer conditions with different load masses(no-load,100 kg,200kg,300 kg,400kg),the active air cooling and phase change material active air cooling systems are designed and studied,and the heat dissipation effects of the battery pack under different transfer conditions of the operating platform after using the two heat dissipation systems are analyzed.The main work and conclusions of this paper are as follows:(1)The thermal model of the power battery of the crawler platform is established by analyzing the heat generation mechanism of the power battery of the crawler platform,testing the internal resistance characteristics of HPPC and calculating the thermal physical parameters of the battery.The temperature rise test of the single battery is designed to verify the thermal model of the battery.The results showed that the simulation temperature rise curve at the battery temperature measuring point had the same trend as the actual temperature rise curve,and the temperature rise error was 9.1%,which indicated that the established battery simulation model could well simulate the heat generation of the battery.(2)By testing the discharge current of the battery pack at different load masses on the level road and ramp of the crawler platform,the temperature distribution of the battery pack under different transfer conditions was simulated.Combined with the optimal working temperature range of the battery pack: the temperature is 20～40 ℃,and the maximum temperature difference is less than 5 ℃,the heat dissipation demand of the battery pack under different transfer conditions was analyzed.The results showed that when the ambient temperature was 25 ℃,the maximum temperature and the maximum temperature difference of the battery pack were in the optimal working temperature range,and there was no need for heat dissipation.When the ramp load was 200 kg,300kg and400 kg,the maximum temperature and maximum temperature difference of the battery pack exceed the optimal operating temperature range of the battery,and the battery pack needed heat dissipation treatment.When the ambient temperature was 35 ℃,the maximum temperature of the battery pack under different load mass conditions on the level road and ramp of the crawler operation platform exceeded 40 ℃,and the battery pack needed heat dissipation treatment.(3)According to the actual structure of the battery box of the crawler operation platform,an active air-cooled cooling system was designed.By analyzing the influence of the inlet wind speed,the vertical spacing of the inlet and outlet and the angle of the inlet and outlet on the cooling effect in the cooling system,the upper and lower spacing of the inlet and outlet and the angle of the inlet and outlet in the cooling system were optimized by using the method of ternary quadratic regression orthogonal combination design.The results showed that when the inlet wind speed was 3m/s,The upper and lower spacing of air inlet and outlet and the angle of air inlet and outlet were 33.4mm and 16.8 °respectively,and the heat dissipation effect was the best.The optimized active air cooling system was used to heat the battery pack of the crawler platform under different working conditions.The results showed that when the ambient temperature was 25 ℃,the designed active air cooling system could meet the heat dissipation requirements of the battery pack under flat road and ramp conditions.When the ambient temperature was35 ℃ and the ramp load mass was 100 kg,200kg,300 kg and 400 kg,the designed active air cooling cooling cooling system was used to cool the battery pack.The maximum temperature of the battery pack still exceeded 40 ℃,which could not meet the use requirements of the crawler platform.(4)According to the heat dissipation requirements of the battery pack of the crawler platform,the EG(expanded graphite)-pw(Paraffin)high thermal conductivity composite phase change material was selected as the heat conducting medium,and a phase change material active air cooling heat dissipation system with an air channel between the phase change materials was designed.By analyzing the influence of the number of air channels and pore size in the phase change material on the heat dissipation effect,it was determined that the number of air channels in the phase change material was 8 and the pore size was4 mm,and the optimized phase change material was used to dissipate the heat of the battery pack.The results show that under natural convection,the heat dissipation of the battery pack with phase change materials could effectively improve the internal temperature consistency of the battery.However,when the crawler operating platform was under the five working conditions of 25 ℃ ramp load of 400 kg and 35 ℃ ramp load of 100 kg,200kg,300 kg and 400 kg,the maximum temperature of the battery pack was still higher than the optimal operating temperature range of the battery.In order to further reduce the maximum temperature of the battery pack under various transfer conditions,active air and phase change materials were added in the battery box to further dissipate the heat of the battery pack.By analyzing the influence of the vertical distance between air inlets and outlets,the angle of air inlets and outlets,and the inlet wind speed on the heat dissipation effect in the active air cooling heat dissipation structure,the upper and lower distance between air inlets and outlets and the angle of air inlets and outlets in the heat dissipation system were optimized by using the method of ternary quadratic regression orthogonal combination design.The results showed that when the inlet wind speed was 2m/s,the distance between air inlets and outlets and the angle of air inlets and outlets were 52.923 mm and 39.357 ° respectively,and the heat dissipation effect of the battery pack was the best.The optimized phase change material active air cooling heat dissipation system was used to dissipate the heat of the battery pack of the crawler operation platform.The operation platform was under the conditions of 25 ℃ and 35 ℃ambient temperature,flat road and ramp,and the working temperature of the battery pack was within the optimal working temperature range to meet the heat dissipation requirements. |
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