Regeneration and Transmission Characteristics to Reduce Fuel Consumption in Heavy Highway Trucks 902226

During the past decade the development of slow speed, turbo-charged and intercooled diesel engines with characteristics to match 9 or 12 speed mechanical transmissions, the use of aerodynamic drag reducing devices, the adoption of radial ply tyres and other mechanically efficient devices has enabled the current semi-trailer tractor to approach the peak of realisable efficiency.

The addition of energy storage is perhaps the only method of further reducing the fuel consumption since the utilisation of the potential energy obtained on downhill running for subsequent hill climbing increases the average speed whilst maintaining the same maximum speed. As an energy storage system is most likely to be incorporated with an effective, continuously variable transmission (CVT), the engine can always be operated at maximum efficiency and at lower engine speeds, thus reducing the wear rate. The use of a non-conventional transmission also has the potential to reconfigure the semi-trailer-tractor layout which may lead to further reductions in the aerodynamic drag, e.g by eliminating the drag due to the vertical slat between the tractor and trailer.

This paper describes the advantages of reducing aerodynamic drag and incorporating energy storage devices of 5 MJ or more with power levels in excess of 2OO kW. The fuel saving potential between 15 and 20% has been determined by the use of Monte Carlo simulation and with realistic CVT efficiencies.