EXPERIMENTAL CHARACTERISATION AND MODELLING OF TURBOCHARGER HEAT TRANSFERS UNDER STEADY AND TRANSIENT CONDITIONS

摘要

In the field of the automobile propulsion, environmental issues (drastic reduction of greenhouse gases) and diminishing fossil fuels supplies enhance the need of fuel consumption reduction. To reach this goal, it is possible to increase the engine specific power at constant rotational speed (Downsizing). The degradation of the transient engine performance limits the expected benefits of downsizing. Engine manufacturers try then to improve turbocharger matching using simulation codes. An analysis of the models included in those codes shows that the turbochargers performance calculations are based on a simple interpolation in the turbochargers maps. In that case, the major assumption is that compression and expansion are adiabatic. For highly turbocharged engines, experiments on test bench show that this assumption is not acceptable. As a consequence, simulate codes provide inaccurate results for certain operating points. In this context, this study proposes new methods to experimentally specify and to model heat transfers in turbochargers and evaluates the incidence of heat transfers on the turbocharger performances. The experimental set up developed in the laboratory aims to understand and evaluate the repartition of heat transfers in the different parts of the turbocharger and then to propose a model of this repartition. Finally, the influence of heat transfers on the turbocharger performances is investigated for steady and transient running conditions.