Model of Aerodynamics and Heat Transfer of a Turbocharger

This thesis deals with the modeling of aerodynamics and heat transfer of a turbocharger for passenger cars. It aims to quantify the heat transfer of a turbocharger and to improve the 1D simulation by considering the effects of heat transfer. The first part involves a measurement study of a turbocharger on a hot gas test bench under both adiabatic and diabatic conditions to obtain the turbocharger aerodynamic characterizations as well as the heat transfer behavior under different thermal conditions. In the second part, a numerical analysis of heat transfer is carried out by using conjugate heat transfer (CHT) simulation for the turbine and compressor, respectively. With respect to the turbine CHT simulation, a new approach (i.e., combined-CHT) is proposed to improve the resolution of the external convection while maintaining the computational cost. The combined-CHT simulation is shown to offer reliable modeling of the turbine heat transfer with a computational cost comparable to that of the ordinary single-CHT simulation. As for the compressor CHT simulation, an analysis of the influence of heat transfer on the characterization process is carried out. The measured compressor efficiency is observed to be up to 15 percent lower than its actual value under these conditions. In the third part, a new 1D/3D-FEM (Finite Element Method) model is developed for the turbocharger, combining the 1D model for the flow field and 3D FEM model for the turbine housing and compressor housing. It aims to consider the heat transfer in a 1D simulation, which is usually employed for the engine simulation. The estimated turbo speeds and compressor outlet temperatures from the two models are comparable, while the 1D/3D-FEM model is shown to greatly reduce the error of the estimated turbine outlet temperatures. Furthermore, the 1D/3D-FEM model is expected to be applicable to turbochargers with a variety of configurations in different operating scenarios.