Simple tank-to-wheels analysis tool for future vehicle powertrains

Abstract

The future powertrains have to be properly assessed in early stages of vehicle design using simple and fast but reliable tools. The aim of the paper is to develop a simulation tool suitable for any of current transient cycles for finding of upper limits of tank-to-wheel efficiencies of recent or future vehicle powertrains in different concepts of vehicles to assess their potential, to find gaps between the state-of-the-art and to find ways to bridge them. The simulation philosophy and procedure may be described in the following steps. The testing cycle power demands on vehicle movement are analyzed and the optimum operation efficiency of a primary mover (engine, fuel cell, electric motor) is assigned to them. Dynamic torques at powertrain are accounted for. Speed, speed slip (driving machine/wheels) and load dependencies of transmission efficiency are simulated by simple models. In the case of a hybrid solution, charging and discharging efficiencies of energy accumulators and additional losses (e.g., in converters and inverters) are considered. The clear modular structure of the simulation tool enables the researcher to amend new features of powertrain components. The links to more detailed simulation tools are prepared. The simulation tool is described by regression and algebraic models (based on the results of higher level simulation tools) in a way giving immediate response during sensitivity analysis. The examples of tool calibration for different powertrains and results comparing powertrain potential are presented for lower medium class passenger car. The current simulation tool creates a useful link between detailed and accurate but CPU time demanding 1-D tools, based on partial differential equations, and rules-of-thumb, used sometimes for initial potential assessments. Moreover, the described tool does not require detailed data on the powertrain during early stage of design but it shows its potential for further development