Design And Optimization Of Structure And Material Of Composites Flywheel Rotor For Electric Vehicle

The flywheel, as a new perfect battery for energy storage system, has more advantages such as being environmentally friendly, green, lightweight, efficiency, and long working life than other traditional energy storage systems. It could be used in the fields of electric automobile, navigation engineering and aerospace engineering, electric power balance, and so on. Therefore, it is considered as a promising and excellent energy storage system and has been a focus for study.In order to obtain higher energy density, the flywheel is made of high strength CFRP (carbon fiber reinforced plastic) and aluminum alloy. Lately, the limited speed of flywheel rotor has been increased to 200,000 rpm, and the energy storage density has been increased to 134 Wh/kg. Moreover, the theoretic energy storage density could reached 306 Wh/kg.Nowadays, the key problems of evalucated model of the composite flywheel rotor are that resulted from the lack of mechanical theoretic foundation, more costly material cost, complex manufactured process, and the shortage of reliability study and test and so on.For the model of flywheel rotor in the thesis, the weight of aluminum hub is 13.5 kg, and the weight of composite rim is 14.5 kg. Moreover, the multi-ring s flywheel rim was made by filament winding process. The inner rings were made of T300 carbon fibre, and the outer rings were made of M40J carbon fiber.Then, according to the basic theory of elastic mechanics and composite mechanics, basic equations and Fortran program for the multi-ring composite flywheel rotor were presented. By the evaluation program. Different results obtained from different thickness and materials of the rings were compared and analyzed. By the analysis, it was found out that the key control factor determined the speed limit and storage energy was the poor transverse tension strength of the composites. Therefore, if only fibers of high longitudinal tension strengths were used in the rim, high rotate speed and high energystorage density of flywheel rotor would not be achieved.On the other hand, for the pre-press stress being threw by the hub was inserted after cooling with liquid nitrogen, the poor transverse tension strength of the multi-ring flywheel rotor could be counteracted. So the rotate speed and energy storage density can be increased efficiently.Finally, based on the elasto-plasticity theory, plastic design and analysis for metal hub of flywheel was performed. Then, numerical simulation and evaluation for the total flywheel system was performed by the FEM software. By plastic design, the speed limit of the flywheel was 42038 rpm, with the energy storage value of 3.6 KWh, and the energy storage of 129 Wh/kg (which is 49% more than elastic design ).