Study On Ammonia Working Medium Automobile Air Conditioning System And Its Control Strategy Of Electric Vehicle

In 2006, European Union passed the Instruction of Automotive Air Conditioning System. According to the instruction, since 2011, all new cars sold in Europe must use the refrigerants which GWP value is less than 150. But until 2017, all cars sold in Europe must use low GWP value refrigerants.At present, R134 a refrigerant is widely used in automobile air conditioning system, but its GWP value as high as 1430, far more than the specified value of European Union, will be eliminated in the near future, but adopt what kind of refrigerant to replace R134 a is not yet clear. At present, around the world, researchers mainly study and discuss these potential refrigerants, such as R1234 yf, C02, R152 a etc. But through study, found that these refrigerants are not the ideal alternative refrigerants. In view of this, this paper puts forward using ammonia as alternative refrigerant of R134 a, and applies to the electric vehicle air conditioning system. Why apply to the electric vehicle air conditioning system, mainly consider that electric vehicles have no fuel system, will be more safe and reliable when using ammonia refrigerant. Based on this, this paper made a study and design of ammonia working medium automobile air conditioning system for electric vehicles.At present, most of electric vehicle air conditioning system control strategy using fuzzy control, but fuzzy control relies on the precise formulation of fuzzy control rules. But for electric vehicles, people's control experience and expert knowledge is very limited, often difficult to establish accurate fuzzy control rules, this may lead control accuracy is not high, and the dynamic quality is poor. In view of this, this paper puts forward using the feedforward fuzzy control strategy as the temperature control strategy of the electric vehicle air conditioning system.In this paper, the research contents and main results are as follows:(1)Made a comparative study for some low GWP value refrigerants, Such as ammonia, R1234 yf, C02, R152 a. Through study, found that ammonia had better energy conservation and environmental protection, at the same time, ammonia is easy to be gained and the price is low, so it can be used as an alternative refrigerant for R134 a in automotive air conditioning system.(2) Made a particular research and design for ammonia working medium automobile air conditioning system of electric vehicle, at the same time, computed its theoretical COP, the theoretical COP is 4.09.(3) Made a research and design of the feedforward fuzzy control strategy for ammonia working medium automobile air conditioning system of electric vehicle. In fuzzy control, the temperature deviation and temperature deviation change rate were inputs, compressor speed revised value was output, 25 control rules were formulated according to the principle of fuzzy control. In feedforward control, made a study and analysis of the disturbed heat load, found that the disturbed heat load was associated with these parameters, the parameters contained vehicle's speed, the temperature of the outside cabin, the temperature of the inside cabin, the sun radiation intensity which is on the ground, time, longitude, latitude, sequence number of the calculated day in a year, the vehicle's driving direction, the number of passengers, electric engine room temperature, the relative humidity of the outside cabin, the relative humidity of the inside cabin.(4)Made a simulation research for the disturbed heat load in Matlab/ simulink, found that the disturbed heat load first increased, then decreased, reached maximum value at about half past 13, about 3550 w. As the number of passengers, vehicle's speed, the relative humidity of the outside cabin increasing the disturbed heat load was increased. With the vehicle's driving direction from the south gradually changed to east, the disturbed heat load decreased.(5)Made a simulation research for the feedforward fuzzy control strategy in Matlab/ simulink. The simulation results showed that feedforward fuzzy control strategy can realize precise control of the cabin temperature.