The Flywheel Energy Storage System Of The Vacuum Device Research

With the rapidly expanding of solar power, wind power and other new energy, and with the increasing demand for peaking power, clean energy storage UPS and rail transportation, the flywheel energy storage technology has become a hotspot of current research prospects and its application are extremely broad.Nowadays, domestic and foreign flywheel energy storage system are using an external vacuum devices to vacuumize the flywheel energy storage system, which has many disadvantages such as energy loss, taking up space and restricted by the installation location. In this paper, the original idea "self-pumping vacuum devices for flywheel energy storage system" is put forward.In the paper, the whole program of self-pumping vacuum device is determined that the self-pumping vacuum device consists of a pump rotor with a helical blade, built-in pump and retaining net and so on, and the shaft makes the pump rotor and flywheel rotor link together as a flying coaxial system, and the pump rotor is divided into three regions the turbine blades area, the connecting transition area and the spiral groove area. This program makes the self-pumping vacuum device compacted, low power expended, fast vacuumized and low cost. According to the structure of self-pumping vacuum device and theoretical model of two-dimensional molecular pump exhaust, the formula of the device’s pumping speed under different flow pattern is derived.In the paper, the finite element analysis software ANSYS is used to simulated the pump rotor of self-pumping vacuum device. The simulation shows the stress distribution and deformation of pump rotor’s different speed, and when the operating speed reaches its maximum speed (36000r/min), the maximum stress is87.5MPa, which occurred at the circumference where the axle hole of pump rotor is connected with the fly, and is much less than the yield limit. The maximum radial displacement is0.762mm, which occurred at the inner hole on the top of the pump rotor, and it’s determined that the space between the pump rotor and the built-in pump body is lmm. According to the requirements of the interference fit and the stress magnitude of the simulation, it’s further determined that the amount of interference size of the pump rotor and the fly wheel ranges 0.03mm～0.055mm.In order to better simulate gas flow of exhausting in the pump rotor spiral tank of self-pumping vacuum device, in the conditions of viscous flow and slip flow, the simulation uses computational fluid dynamics (CFD method); in the conditions of free molecular state and the transition state, the simulation uses the direct simulation Monte Carlo (DSMC method). Through simulating and calculating the self-pumping vacuum device, we can get the results of pumping speed and the relationship between the calculation pumping speed and the revolving speed, and it’s obtained that in the high vacuum, the self-pumping vacuum device exhausts efficiently, and the better pumping speed of this device ranges from12000r/minto60000r/min.After testing the pump rotor displacement of the working self-pumping vacuum devices and comparing the test results against the theoretical data of pump rotor displacement, it shows that the maximum error rate of the experimental results and theoretical results is17.1%. Through the experiments of the external vacuum system and the self-pumping vacuum system vacuumizing the flywheel energy storage, it’s obtained that the maximum error of the test data and simulation results of the self-pumping vacuum device’s pumping speed is13%, and it demonstrates the best preceding working speed of the self-pumping vacuum device. From the experiments of these two systems vacuumizing the flywheel energy storage, it indicates that the self-pumping vacuum system costs12%of the time external vacuum system costs to reach0.01Pa. The results of the energy consumption test show that the energy loss of the self-pumping vacuum system is29.2%of the external vacuum system’s, and compared against the external vacuum system, the self-pumping vacuum system reduces34.86%energy consumption of the flywheel energy storage system.Research shows that the self-pumping vacuum devices for flywheel energy storage system has many advantages such as structure compacted, short vacuumizing time and small energy loss.