Vehicle model for transient simulation of a waste-heat-utilisation-unit containing extended PowerTrain and Fluid library components

Abstract

DLR Institute of Vehicle Concepts uses MODELICA for vehicle simulation. One major application is the power train analysis with regard to fuel consumption, emission and performance. The multidomain approach of MODELICA has already been a benefit when describing alternative vehicle concepts like fuel cell vehicles and hybrid vehicles. This paper describes the first approach modelling another concept of low-emission vehicles, i.e. a vehicle powered by an internal combustion engine (ICE), where a waste-heat-utilisation-unit in the exhaust system is applied. The recovery and conversion of waste heat in the exhaust system of ICE-powered vehicles is very attractive, because as a rule of thumb about one third of the fuel energy is emitted with the exhaust to the ambient. There are several approaches to convert exhaust energy into useful energy, e. g. applying a thermal engine, which is powered by the exhaust. Another possibility are thermoelectric devices, which convert heat into electricity. However, in almost all concepts for waste heat utilisation a heat exchanger in the exhaust system has to be integrated and additionally a heat sink has to be provided to run the complete process. As an example for a waste-heat-utilisation-unit a thermoelectric device is considered in this paper. To predict the performance of such a thermoelectric device in vehicle operation the PowerTrain library [1] has been extended with elements of the Fluid library for representation of the exhaust system. Most imortant a special heat exchanger model has been developed which describes the thermoelectric device. The paper gives an overview over the modelling approach of the complete system and the component models respectively. Finally, first results of simulation runs are given.