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This investigation represents work on a model to determine heat flows on turbochargers. Recently, a power-based method has been developed to compare adiabatic and hot gas tests from radial turbines and compressors. Moreover, this method has shown the ability to correct standard measurements in terms of heat flows. In this investigation, a wastegate turbocharger has been investigated from a small gasoline engine. For validation purposes of the isentropic efficiencies, a conjugate-heat-transfer (CHT) simulation has been carried out on the turbine. Results have shown that isentropic efficiencies fit well for values of turbine inlet temperatures of 600 °C between corrected data and the simulation. For other temperatures, the differences between the determined values and CHT are greater. The differences rise with higher temperatures generally. So, the objective of the investigation is to improve the existing method for determining turbocharger heat transfers. Hence, an additional dependency of turbine inlet temperatures has been implemented in the approach and tested for T3 = 400 °C, 600 °C, 800 °C, and 950 °C. The modification has shown better results and smaller differences to CHT simulation. Especially, at low speeds where the former approach has had big differences, the modification improves the distribution for the investigated turbine inlet temperatures.

Heat transfer and inhomogeneous flows in the turbine inhibit the calculation of the isentropic efficiencies from hot gas test data using conventional methods. In previous works the basis for such a calculation has been built such as special measurement devices and a power-based approach for calculating the heat flows. The main objective of the present work is the calculation of the isentropic turbine efficiencies and further development of the approach for obtaining isentropic compressor efficiencies from hot gas test data. The turbocharger is described aerodynamically and thereby the friction power can be calculated by setting up the power balance. For validation of the compressor, adiabatic measurements are used as well as CFD simulations for the turbine. Reasons for the latter are changing inlet conditions that do not allow the transfer of adiabatic data to diabatic or hot conditions.

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