Study On The Performance And Optimization Design Of Fuel Cell System For Electric Vehicles

Optimization design and performance evaluation of the fuel cell system is animportant research direction for the fuel cell electric vehicle. Therefore, based onstructure, properties and function of the proton exchange membrane fuel cell stackand the fuel cell auxiliary system, this study puts forward the calculation theory andmethod of proton exchange membrane fuel cell system for vehicle, constructed acomplete output performance model of the fuel cell system, conducted optimizationresearch point at the output performance of the fuel cell system, tested and validatedthe method and numerical model. The main research and innovations are as follows:First of all, the fuel cell stack is a key component of the proton exchangemembrane fuel cell system. Design and research of the system involvesmulti-disciplinary field of electrochemistry, physical, mechanical and electronics.Therefore, a comprehensive analysis of the advantages and disadvantages about themodeling theory and method of the proton exchange membrane fuel cell stack isconducted, this study takes the fuel cell stack output performance as main objectivesof research, from the perspective of fuel cell stack, developed the theory and methodof the voltage, activation overvoltage, ohmic overvoltage and concentrationovervoltage of the fuel cell stack, so as to build the output performance model offuel cell stack. This model combines the advantages of modeling methods both theexperience model and theory model, the measured data of a fuel cell was ensured theaccuracy of the model, and mathematical formula of the theoretical model wasimproved the versatility and portability of the model, laid the foundation for thenumerical model and design optimization of the fuel cell system.Second, a complete fuel cell system consistes of a fuel cell stack and fuel cellauxiliary system. The fuel cell system in addition to the fuel cell stack, there mustalso be a fuel cell auxiliary system, such as cooling system, humidification system,oxygen and hydrogen supply system etc.. The performance of the fuel cell systemdepends not only on the fuel cell stack, but also on the fuel cell auxiliary system.These auxiliary system not only guarantee the normal operation of the fuel cell stack,also seriously affected the output performance of the fuel cell system. However, thereare few quantitative research about the auxiliary system effect on fuel cell systemperformance in existing numerical model of fuel cell system. Therefore, based on structure and function of the proton exchange membrane fuel cell auxiliary system forvehicle, this paper analyzes the main mode and mechanism of the fuel cell heating andcooling, improved the theory and calculation method of the fuel cell heating andcooling, developed the fuel cell heating and cooling numerical model. From point ofview the performance of the fuel cell auxiliary system, provided the theory and thecalculation method of air compressor, cooling water pump, cooling fan andhumidifying pump of the fuel cell auxiliary system, build a quantifiable performancemodel of the fuel cell auxiliary system. The model fully reflects the performance ofthe components of the fuel cell auxiliary system for fuel cell vehicle, providedcollaborative optimization research on effective, had better practicability anduniversality, developed the new theory and method for the design optimization of fuelcell auxiliary system.Third, based on the fuel cell stack model and the auxiliary system model, acomplete output performance model of the proton exchange membrane fuel cellsystemfor vehicle was build in this dissertation, The optimization method using feasiblemultivariable for proton exchange membrane fuel cell system of fuel cell vehicle wasproposed, and the sequential quadratic programming and interior point method weredeveloped to optimize the output performance model of fuel cell system. Theoptimization results show that the fuel cell system model is effective to optimize theoperating parameters of the fuel cell system, the output power of the fuel cell systemoptimized is increased by26%, provides a valuable theory basis and calculationmethod for performance improvement of the whole fuel cell vehicle and designoptimization operating parameters of fuel cell system of electric vehicle.Fourth, using the test platform and fuel cell vehicle at the fuel cell laboratory inUniversity of Victoria, Canada, comparative experiments were conducted for the fuelcell vehicle before and after the optimization. The experimental research shows that,the comprehensive dynamic performance of the fuel cell vehicle optimized haveimproved markedly, using the calculation method, numerical model and optimizationmethods of the fuel cell system proposed in this paper, the maximum accelerationincreased by25%, the maximum speed increased by7.3%among them, and thecorrectness and effectiveness of the fuel cell system numerical model andoptimization methods was further verified.