Performance Simulation Of Vehicle Fuel Cell Powertrain Systems

Energy and environment crisis stimulate the world automotive industry to find cleaner and more efficient sustainable power sources for transportation. There is an increasing interest in the use of PEMFC (Proton Exchange Membrane Fuel Cell). However, the research about fuel cell vehicle powertrain system is just beginning and the efficiency advantage of fuel cell system (FCS) to traditional ICE is not fully realized. In order to increase the efficiency of fuel cell vehicle powertrain systems, by applying simulation techniques, the dissertation focused on several main factors which influence the efficiency of FCS and fuel cell powertrain systems and studied several improving methods and presented the results of them.At first, based on Matlab/Simulink software environment, a fuel cell simulation platform was set up by using both experimental and electrochemical mathematical methods. According to specific fuel cells, the platform can build specific models which are able to exactly show the influence of various parameters such as pressure, reactant stoichiometry, humidity and temperature to fuel cells' performance. The good fitting with real test data indicated the effectiveness of the built models.Based on the fuel cell simulation platform above, the parameters optimization of fuel cell air systems and application of turbocharger as an energy recovery were studied as methods to decrease the air system's parasitical power and increase the FCS' efficiency. The results indicated that for better system efficiency and greater peak power output, the air pressure need increase as the load increases, while the air stoichiometry should be kept in the range of 1.5~2.5; the application of turbocharger can effectively improve the FCS' performance and the max improvement of efficiency and peak power are 5% and 15% respectively, and the efficiency improvement is greater at heavier load. In addition, a humidifying-cooling coupling system model was set up to gain deeper understanding of air system parameters optimization. The results showed that the air pressure will decrease and the stoichiometry will increase when the humidifying-cooling coupling system was added into the FCS models. A fuel cell vehicle powertrain system configuration without high power DC/DC converter is also studied in contrast with the configuration which has high power DC/DC converter in order to avoid the disadvantages of high power DC/DC converter in efficiency, security and reliability. In the former case, the fuel cell output voltage can be narrowed at low load by adjusting the FCS' working parameters. The results showed that comparing with the configuration with high power DC/DC converter, the new configuration can improve the powertrain system efficiency by 1.5%~5% and promote the peak power by 2.5%, while still satisfy the motor input voltage in the permitted range.The performance of fuel cell powertrain systems can be improved by applying air system exhaust energy recovery and parameters optimization and elimination of high power DC/DC converter between FCS and driving motors. The conclusions above provide useful reference to the developing direction of fuel cell vehicle powertrain systems.