Study On Design And Parameter Matching For Air Conditioning System Of Electric Bus

Electric vehicle (EV) in use will not cause any pollution to the environment, really be able to achieve zero emission. At the same time, electric energy can come through various forms of energy, and in comparison with petrol, the cost of using electric energy is much lower, therefore, EV is a more satisfactory solution to change the dependence of the automobile on oil at present.Like the conventional vehicle, EV also need to provide a comfortable environment for the passengers, so air-conditioning system (ACS) is indispensable. However, because of the great energy consumption, ACS will become a heavy burden to the EV battery when it is working, The range of EV will be seriously affected. Thus developing energy-saving and efficient ACS has gradually become an important topic in the area of the new energy vehicles.Based on an electric bus (EB), this paper studies on the parameter matching and system design for the ACS of the EB. Since the air-conditioner compressor is driven by separate motor, the speed and power of the compressor can be regulated in accordance with the cooling load of the ACS. First, this paper calculates the air-conditioner cooling and heating load according to the EB structure parameters. then, on the basis of the load results, the paper matches the relevant parameters of the ACS and chooses the model of the system. through that process, the air-conditioner energy consumption will be reduced from the source, and it also provides a basis for the further study on the air-conditioning achieving energy consumption of on-demand under a proper control strategy.Firstly, the paper compares the ACS for EV with that for conventional vehicle. It presents the importance of optimizing and correctly matching the parameters of the ACS. On the basis of reading a large amount of literatures, this paper describes the research status of the ACS for EV at home and abroad.Secondly, through collecting the relevant meteorological data and analyzing a variety of environmental disturbance which affect cooling and heating load of the ACS, the paper makes clear the inside and outside ambient parameters for cooling and heating load calculation of the ACS. To the cooling load, the paper first discusses the difference between the heat gain and the cooling load, after builds the mathematical model of the cabin heat gain, the paper converts the heat gain to the cooling load by Z transfer function. To the heating load, the paper builds the model of space heating load and defrosting load. Then, using the above calculation model Combined with the vehicle body structure parameters, the paper calculats the cooling and heating load.Thirdly, the paper analyzes on the advantages and disadvantages of three air conditioning solution for EB such as heat pump air-conditioning, single refrigerant system and electric heating system. Then, it selects the solution of single refrigerant system equipped with electric heating system for the prototype vehicle, that will bring little change to the vehicle body and easy to realize. The paper confirms the driving mode of the air-conditioner compressor, makes a detailed analysis on the technical advantage of selecting the scroll compressor and the brushless DC motor, introduces the speed regulating system and the control principle of the driving motor. At the same time, it also chooses the types of the heat exchangers and the throttle expansion valve, gives the arrangement form of the ACS on the vehicle.Fourthly, starting from refrigeration principle of the air-conditioning, the paper confirms the running condition and the thermodynamic cycle of the system, based on the application conditions of the ACS for the EB. By introducing the Calculation Model of the air-conditioning thermodynamic cycle, combined with the anterior cooling load results, the paper calculates the parameters of the ACS and analyzing the relationship of the Related Parameters. At last, it confirms the selected compress and motor types according to some companys' performance indexes.Finally, the paper constructs the simulation model of the prototype vehicle using Matlab/Advisor, analyzes the affection of the use of the air-conditioning to the power performance and the range of EB. The compress power involved in the simulation is obtained from the average cooling load of the design day, which reflects the power demand of the electric compress based on a speed regulating system. The results of the simulation show that on the one hand, whether the use of the air-conditioning has effect on the power performance or not is determined by output power of the Battery, it is for the reason that the input power of the air-conditioning comes from the battery but not from the vehicle driving motor. On the other hand, the use of the air-conditioning will greatly reduce the range of EB, the degree of the reduction varying with different driving cycle.