Flywheel Based Mechanical Hybrid System: Simulation of the Fuel Consumption Benefits of Various Transmission Arrangements and Control Strategies

Abstract

Flywheel based mechanical hybrid technology is under development for Motorsport, Automotive and Commercial Vehicle applications. Originally a European development, North American mechanical hybrid applications are now underway. The mechanical hybrid system recovers kinetic energy from the vehicle during braking to a high-speed, rotating flywheel via a variable drive system. When compared to an electric motor / battery arrangement, the mechanical hybrid system offers benefits in cost, weight, package, efficiency and ultimately fuel consumption. A number of UK Government funded projects applying flywheel based mechanical hybrid systems are ongoing, developing the technology and building mechanical hybrid equipped demonstrator vehicles. Participants include OEM’s Jaguar Land Rover, Ford, JCB and Optare using advanced technology from Allison Transmission Inc, Flybrid Systems, Ricardo, SKF and Torotrak. The Torotrak torque controlled, variable drive technology is a key component within the mechanical hybrid system. As part of the development process, all aspects of the mechanical hybrid system are under investigation (such as the required energy storage, rates of energy recovery, etc) including the variety of different physical architectures for the variable drive system. Multiple configuration options are available including direct drive, epicyclic shunted, range extended CVT and epicyclic shunted IVT arrangements. In addition, the flywheel and variable drive system can be connected to the powertrain in a variety of different locations from engine to transmission to final drive. This paper describes the simulation of the mechanical hybrid system with focus on the impact on the fuel consumption benefit, over multiple drive cycles, of the variable drive configuration, the location of the variable drive & flywheel system and the control strategy options.