Regenerative Drive for Subway Trains—Part 1: Mechanical Accumulator Design

A regenerative drive system for subway trains is mathematically modeled and numerically evaluated for the Toronto Bloor-Danforth Subway Line. The scope of the study dictates a multipaper presentation of system and component modeling. This first paper designs and optimizes the mechanical accumulator subsystem (bearings, seals, losses) of the vehicle propulsion package. Preliminary design criteria (stress-energy relationships) predict the required performance capability of the one and two accumulator per vehicle systems; the need for high energy densities is of secondary importance compared to the required power density for vehicle operation. Accumulator performance tests suggest ease of integration with the current drive system. Subsequent papers model the external and internal drive systems, and numerically optimize the flywheel control concept and accumulator size; day savings, on a round-trip basis, are predicted in the order of 26 percent.