Decoupling Vehicle Work from Powertrain Properties in Vehicle Fuel Consumption 2018-01-0322
The vehicle contribution to fuel consumption is shown to be proportional to the total work required to drive the cycle due to vehicle mass, tire friction, and aerodynamic drag. The rate of increase of fuel with work is narrowly defined over a wide range of applications because it derives from the marginal efficiency of the engine. The theoretical basis for this prediction is reviewed. Examples from current applications are discussed, where a single powertrain is used across several vehicles. Finally, a proprietary cycle simulation model is used to predict fuel consumption for existing vehicles over a range of road loads and powertrains. The modelling confirms the linear dependence of the fuel consumption on vehicle work. In addition, the linear dependence scales across different powertrain sizes, and therefore performance levels, when the same powertrain technology is used. Variations in vehicle design can therefore be decoupled from the powertrain’s operation, resulting in a convenient simplification of fuel consumption estimation. Separate figures of merit for the vehicle work and for the powertrain efficiency are defined. This is useful in both quality control of experimental results and in upfront estimations of vehicle variants.