A general procedure is developed to optimize the geometry, rotor material and operational parameters of a mechanically driven flywheel system with respect to the total power loss. Using a fixed energy storage capacity, an optimal outside rotor radius exists for every rotor mass because of the counteracting influence of the air friction losses with the bearing and seal friction losses. In view of system packaging, the outside rotor radius will normally not be taken at its optimum, but decreased to a more preferable dimension at the cost of an increase of the total power loss. Without changing the outside rotor dimensions the total power loss can be reduced by using a ring-shaped rotor, with an optimum inner to outer radius ratio of approximately 0.7 and by using a material with a higher density. There is no optimal rotor mass: the total power loss is decreasing with an increasing rotor mass. However for automotive application the maximal allowable rotor mass is restricted. Once the geometry is known, the housing geometry and vacuum system can be optimized. For the EUT-I flywheel system the optimal ratio of side plane gap width to outer radius and ratio of circumferential gap width to outer radius is approximately 0.05. With obtained values for the power needed to drive the vacuum pump and the air leakage through the static and dynamic vacuum seals, an optimum for the air pressure pair is found near 1 mbar.
Design optimization of a compact flywheel system for passenger cars
Optimierung des Designs eines kompakten Schwungradspeichers für Pkw
1999
13 Seiten, 8 Bilder, 1 Tabelle, 7 Quellen
Conference paper
English
Design Optimization of a Compact Flywheel System for Passenger Cars
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