Engine simulation programs presently include the simulation of the engine together with its manifolds and the turbocharger. Most of the existing engine simulation models are based on measured turbocharger performance maps. Usually, these maps cover only a limited operating range. Therefore, they cannot be used to simulate the turbocharger performance at every engine rotational speed and are unable to adequately model part-load performance which in passenger cars prevails throughout most of engine operating life.
The present paper aims at providing a physically meaningful method of turbocharger performance prediction. This method takes into account the heat flow in turbochargers as well as the aerodynamic performance of the compressor and the turbine, respectively. It uses the measured performance maps as a basis for the turbocharger performance simulation, extending the compressor performance prediction down to zero rotational speed.
Engine operating points are simulated using the method proposed above at low turbocharger rotational speeds to investigate the effect of heat transfer from the turbine to the compressor on the engine simulation in this operating range. The computational results of both, zero-dimensional and one-dimensional engine process models, show a better match with experimental data than previous engine calculations with non-physically based turbocharger models.