| As an auxiliary power source,supercapacitors are widely used in trams due to their high power density,excellent low temperature resistance,fast charge and discharge,and environmental protection.They provide convenience for tram power input and bring some problems.Supercapacitors work under extreme fluctuations or extreme temperatures will produce thermal effects,and the internal temperature will rise rapidly in a short time.The applicable temperature range of supercapacitors is generally 233.15～343.15 K.When the temperature exceeds the device allowable,the maximum temperature will seriously affect the electrical performance and service life of the device itself.It can be seen that temperature is an important parameter affecting the output performance of supercapacitors.A reasonable thermal management system can ensure the thermal stability of supercapacitors under steady-state operation of trams and dynamic traction braking,improve the electrical performance of supercapacitors and service life.Therefore,solving the thermal management problem of supercapacitors for trams is of great significance to the safety,stability and economy of the vehicle’s power system.In order to ensure that the supercapacitor works within a suitable temperature and a small temperature difference range,by analyzing the structure and working principle of the supercapacitor,a electrochemical-thermal coupling model of the supercapacitor is established,and its electrochemical performance and thermal characteristics are simulated and analyzed.Designed air-cooled thermal management system and coupled thermal management system for its thermal behavior,and use COMSOL and MATLAB to optimize the parameters affecting the heat dissipation effect,improve the temperature control and average temperature performance of the thermal management system.It has important practical significance for improving the electrical performance and service life of supercapacitors.This paper relies on national key R & D plan tasks(NO.2017YFB1201004-12),taking Maxwell48 V module as the research object,the method of theoretical research,simulation analysis and experiment is used to study the supercapacitor thermal management system for trams.The main research contents and innovation points are as follows:(1)The electrochemical-thermal coupling model was established based on the structure and working principle of supercapacitor.Aiming at the problem of high computational complexity and time-consuming calculation of the thermal-electric coupling model when optimizing the thermal management system,a simplified method of the electrical-thermal coupling model is proposed.Under the same conditions,the simplified model can simplify the electric-thermal multiphysics heat conduction problem into a single-physics problem solution.The error of the calculation result does not exceed 0.65% and the solution speed is effectively improved,laying a foundation for the next optimization of the thermal management system.(2)Build an experimental platform,the accuracy of the model was verified through experiments.On this basis,the electrochemical characteristics and thermal properties of the supercapacitor were analyzed,and the influence curves of changes in electrolyte concentration and temperature on the internal resistance during charging and discharging were obtained.The effects of thermal convection coefficient and ambient temperature on the maximum temperature of supercapacitors were studied.The temperature field distribution of supercapacitors under different space structures is calculated by simulation.The results show that the cubic structure is the best when considering the cooling efficiency and the average temperature performance,the hexagonal structure is better when the space utilization and the cooling efficiency are considered.(3)The best and worst goals of thermal management were formulated.The structure of the air-cooled heat management system and the coupled thermal management system were designed and modeled.The temperature control and average temperature performance of the two thermal management systems were simulated and analyzed.The maximum temperature of the supercapacitor module after the system is cooled is 41.9℃,and the maximum temperature difference is 14℃.Compared with the supercapacitor module under natural convection,the steady-state temperature is reduced by 33.5℃.The maximum temperature of the supercapacitor module using heat pipe-phase change material is used for heat dissipation.It is 28℃,and the maximum temperature difference is 3℃.The results show that the temperature control performance of the air-cooled heat management system has reached the worst target,and the average temperature performance is poor.The temperature control and average temperature performance of the coupled thermal management system are good,but it still needs to be optimized compared to the optimal target.(4)Analyzed the sensitivity of the parameters that affect the heat dissipation effect of the thermal management system.Combined COMSOL and MATLAB to optimize the parameters of the thermal management system to obtain the Pareto non-inferior solution set.Used the ideal point method TOPSIS to sort the non-inferior solutions to obtain the optimal solution.The supercapacitor adopts air-cooled heat dissipation,and the maximum temperature and maximum temperature difference after optimization are reduced by 39.5%and 86.1% respectively compared with before optimization;Using coupled heat dissipation,the optimized maximum temperature and maximum temperature difference are reduced by11.4% and 20%,respectively.The optimization results prove the effectiveness of the joint optimization method,which has certain guiding significance and reference value for the optimization of the actual thermal management system. |
PDF Full Text Request