| The energy crisis, global warming, environmental pollution and other factorshave contributed to the electric vehicles to become the future of automotivedevelopment. Battery pack needs thermal management to ensure its safety andhigh performance. In addition, after power system changing, the vehicle thermalcharacteristics changed a lot correspondingly, which impacts a lot on the airconditioning, especially for heating. Electric vehicles are not only required toprovide comfortable driving environment in cabin, but also required to thermalmanage the battery pack, motor, inverter and other electrical components in ahappy working condition. The performance of thermal management systems andenergy efficiency will directly determine the electric car’s mileage, ridingcomfort and driving safety. Researching and development on thermal systemsand control systems with high energy efficiency, energy saving, stability androbustness will have a high practical significance for the development andpromotion of electric vehicles. Therefore, on the basis of the analysis of currenthigh protential electric vehicle thermal management system options, one electricvehicle thermal management system built and then the performance and energyefficiency optimized by means of theory analysis and experience study. The maincontents and results are as follows.1) The Analytic Hierarchy Process (AHP) engineering evaluation model was builtfor the analysis of electric vehicle thermal management solutions. Some highpertential electric vehicle thermal management options were analysised in thispaper. With the support of expert group decision making knowledge, to carryout the sort of electric vehicle thermal management system solutions based on customer request and its function. Based on the quantitative analysis oftechnical, cost, performance, control, and other factors for each options, thebest engineering application solution for electric vehicle thermal managementsystem abtained. The analysis results show that the independent battery airconditioning unit for the battery thermal management has obvious advantages.Subsequently, through the experimental comparison of two theraml systemswith air-cooled battery and coolant-cooled battery. We found that two thermalmanagement solutions meet the requirement of engineering applications.Relatively speaking, the Coolant-cooling scheme has better air conditioningcooling and heating features, and better battery SOC consumption thanair-cooled scheme.2) The CFD model for HVAC module air side performance analysis was found inthis paper by using the theory of numerical analysis and experimentalvalidation. The maximum error of the model for flow rate is3%. And themaximum temperature error is1.4℃. With the help of CFD analysiscombining with experiment study, the HVAC module designed for electricvehicle was optimized on account of energy saving. The airside resistance,heat pick-up reduced, and the KPI of evaporator improved without decreasingthe comfort index. After optimization, airflow enhanced11%and coolingcapacity enhanced16.6%on full cold mode.16.5%and11.1%enhancementrespectively for airflow and heating capacity as well on full heating mode.Which greatlly improved the energy efficiency of HVAC module.3) The thermal sensing comfort index TCI for passenger, battery and electricalparts established in this paper. And then a feedforward neural networkestablished for forcasting thermal comfort of monitoring components. On thebasis of the characteristics of electric vehicle thermal systems and energysaving goal, combined with the theory of fuzzy neural network control, onefuzzy neural network model for electric vehicle thermal control established inthis paper. TCI index is the control target and HV electric compressor, HV PTC heater, electric water pump, blower, actuator, solenoid valve and etc. arecontrol objects. The main strategy is to find a matching point between allcontrol objects according to TCI index. Which make cabin, battery and HVcomponents reaches set temperature quickly, smaller temperature fluctuations,and lower SOC consumption.4) Based on the purpose of energy conservation, combined with thecharacteristics of the micro-channel evaporator system, one temperaturecontrol system was developed in this paper for electric vehicle cooling system.This temperature control system is more suitable for the micro-channelevaporator air conditioning system of the electric vehicle. The control systemhas better control sensitivity and control response characteristics, thetemperature interval can be set in [0,4]. Minimum evaporation temperaturereaches the freezing point of the condensate, lower than the traditional designwhich uses air temperature sensor with [4,5.5], the minimum evaporationtemperature decreased by2℃. Which achieved the maximum coolingperformance of air-conditioning system.5) The optimized HVAC module and thermal management control system basedon energy efficient strategy were used into the electric vehicle thermal systemwe built in this paper. Then experience performed to study the performanceand control robustness. Compared with the pre-optimized thermal system andtraditional benchmark vehicle, the results showed that: optimum design ofthermal system has better control performance and stability, and can quickrespond to user setting. After optimization, the cooling down performance hasbeen improved significantly and the cooling rate as well, the vent outlettemperature decreased2.2℃, breath temperature dropped2.0℃. There wasno big improvement on heating up performance. Moreover, because of controlstrategy on power limiting of the PTC heater and the engine running intervalsand time duration, there was not no significant difference in heatingcharacteristic before and after optimization. However, the consumption of air conditioning system on battery SOC has been significant improved. Theenergy consumption has been decreased by17%and18%battery SOC oncooling down and heating up conditions respectively. |
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