Global warming is a climate phenomenon with worldwide ecological, economic and social impact which calls for strong measures in reducing automotive fuel consumption and thus CO 2 emissions. In this regard, turbocharging and the associated designing of the air path of the engine are key technologies in elaborating more efficient and downsized engines. Engine performance simulation or development, parameterization and testing of model-based air path control strategies require adequate performance maps characterizing the working behavior of turbochargers. The working behavior is typically identified on test rig which is expensive in terms of costs and time required. Hence, the objective of the research project "virtual Exhaust Gas Turbocharger" (vEGTC) is an alternative approach which considers a physical modeled vEGTC to allow a founded prediction of efficiency, pressure rise as well as pressure losses of an arbitrary turbocharger with known geometry. The model is conceived to use smallest possible number of geometry as well as material parameters. Thus, conventional expensive and time-consuming application processes can be countered and test rig as well as in vehicle measurements can be reduced. Furthermore, the vEGTC model enables the prediction of different turbocharger behavior caused by geometry variations. Within this paper it is shown in which way the radial compressor as a representative modeling component can be described by zero-dimensional equations: in order to simulate the working behavior of the compressor the geometry, the thermodynamic state of the inlet-air and the turbocharger speed are assumed to be known. The loss mechanisms are devised using analytical and semi-empirical loss correlations. In order to validate the compressor efficiency the heat transfer from the turbine to the compressor is considered. Finally, the simulation output is compared to manufacturer maps of three different turbochargers pointing out the reliability of the model. Thus, a comprehensive validation of the vEGTC model is yielded. The object-oriented language Modelica is used for modeling and the simulations are provided by the Dymola solver.

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In addition to developing fans as aerodynamically efficient as possible, acoustic optimization gains more and more importance for the purpose of reducing fan noise exposure. In order to combine good aerodynamic properties with a silent fan, this experimental research investigates the acoustic and aerodynamic characteristics of an axial fan. In this case, a fan with skewed blades is tested in view of its aerodynamic efficiency and noise exposure in dependence on its tip clearance and stagger angle. For this purpose, six different stagger angles and five tip clearance gaps per angle were measured in a fan test rig (according to ISO 5136). Interpretation of the recorded data shows a clear trend toward higher aerodynamic efficiency and less noise with a down-sizing of the tip clearance gap. As the cost of manufacture rises with the decrease of the tip clearance, the efficiency of these measures can be calculated with the results of this study under consideration of aerodynamic and acoustic aspects.

In this paper, numerical results of the mixing behavior of two mass flows having different temperatures in an elbow, which is located upstream of a turbocharger compressor, are presented. The background for these investigations are the thermal problems and the problems due to droplet impacts, which arise as a result of Low Pressure Exhaust Gas Recirculation for a turbocharger compressor. In these investigations, the temperature distributions resulting at the inlet of the compressor are mainly of interest. Of further interest are the trajectories of possibly arising water droplets in the inflow of the turbocharger compressor. In the first step different injection configurations are calculated without the compressor in order to get a first impression of the mixing behavior of two mass flows in an elbow. Afterwards three of the injection geometries are calculated including the compressor to see the influence of the compressor on the mixing behavior. The results show a strong influence of the direction of the injection and of the relative position of the injection to the elbow unit. Subsequently, visualization tests are made to qualitatively check the mixing behavior of the different elbow geometries.

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