Study On The Structural Design Of Carbon Fiber Composite Flywheel Rotor In Large Tension Winding

The composite flywheel energy storage system stands out from many energy storage technologies for the characteristics of high energy density,light weight,high efficiency,long life and no pollution.Due to its high specific strength,high specific stiffness and absence of high frequency eddy current power loss,carbon fiber composites have become the preferred material for the manufacture of flywheel rotor rims.The composite material flywheel rotor produced by the tension-free winding process has low radial strength and can not fully exert the high specific strength characteristics of the composite material.The use of multi-ring interference assembly technology can improve the radial stress distribution of the rotor,but the machining and interference assembly have serious damage to the composite material,and the composite material rim is prone to defects such as damage,crack,burr,avalanche and delamination.The large tension winding technology can not only effectively improve the radial stress of the flywheel rotor,but also avoid damage to the composite material rim by the press-fitting process.Therefore,it is of great significance to study the large tension winding technology to fabricate high performance composite flywheel rotors.In this paper,suitable materials are selected according to the material requirements of the high-speed flywheel rotor,and the comprehensive mechanical properties of the aluminum alloy,the epoxy resin casting body and the three kinds of composites were tested,and the basic material parameters are provided for analytical analysis and numerical simulation analysis.At the same time,the analytical method of axisymmetric flywheel rotor is established based on the assumption of plane stress,and the expressions of stress and strain of the flywheel rotor in large tension winding preparation and high-speed rotation are deduced.The influence of the tension,material collocation and material thickness distribution on the rotor stress distribution at 30000 RPM is analyzed,the best tension system and the thickness of the three kinds of composites are determined.The three-dimensional composite flywheel rotor model was built using ANSYS finite element software.The filament winding tension was applied by the equivalent temperature field method.The winding and curing process were simulated by the element deletion method and the restarting analysis skill.And the contact elements ensure effective transmission of radial stresses.The distribution of the equivalent stress of the shaft and hub and the distribution of the compressive stress at the contact surfaces of the materials are analyzed during the winding process and high-speed rotation.For the insufficiency of the initial design scheme,optimizing the hub structure and improving the connection of the shaft and the hub to improve the stress distribution of the flywheel rotor.Through analytical analysis and numerical simulation analysis,the optimal geometry and process parameters of the flywheel rotor were obtained.The energy density of this composite rotor is 49.7 Wh/kg at operating speed.Four thin-wall composite flywheel rotor test pieces were fabricated by using large tension winding technology.The strain radial stress and the trend of the compressive stress of the rim and hub contact surfaces during the preparation process were measured using strain gages and thin-film pressure sensors.The test value is basically the same as the analytical value and the simulation value.The finite element model in this paper has a high accuracy and is suitable for the simulation analysis of a large tension winding composite material flywheel rotor.Finally,the composite flywheel rotor sample was fabricated based on process parameters and flywheel rotor geometry.