Analyse und Modellierung zweiflutiger Turbinen unter Berücksichtigung der Wastegateströmung

Stadermann, Max; Pischinger, Stefan (Thesis advisor); Wirsum, Manfred (Thesis advisor)

Aachen (2020) [Dissertation / PhD Thesis]

Page(s): 1 Online-Ressource (3, xi, 99 Seiten) : Illustrationen, Diagramme

Abstract

This work investigates the interaction of the turbine bypass (wastegate) with the turbine wheel and the combustion engine. A particular focus is on a extended modelling for the 1D engine process simulation of the double entry turbine under consideration of the wastegate behavior during unequal admission (unequal inlet pressure in the two scrolls).Due to the high complexity of the double entry turbine the wastegate is initially being investigated for a single entry turbine. The results can be summarized as follows: • For the quantification of the flow behavior of the wastegate independence of the wastegate angle and the adjacent pressure ratio, two methods were examined. Measurements with blocked turbine volute, where only the wastegate is admitted. Measurements with a complete turbine stage, where the waste gate mass flow is measured as the difference between the impeller and the total mass flow. With closed Wastegate, the impeller mass flow corresponds to the total mass flow. Both methods lead to comparable results. • The flow of the wastegate shows a not negligible dependence on the turbine pressure ratioΠT,ts, which shows an increase of up to ∆A3,s = 25% (ΠT,ts = 1,2–>ΠT,ts = 3). • The turbine efficiency and flow rate of the wheel can usually be considered independent from the opening angle of the wastegate. The investigations on the double entry turbine based on these findings can be summarized as follows: • The isentropic area of flow A31,s changes for small (e.g. θWG = 6◦) wastegate angles by up to 600% depending on the pressures in both scrolls (the scroll pressure ratio). • The asymmetrical discharge through the two wastegate channels results in a shift of the flow condition upstream of the turbine wheel. • By using the newly developed model, the simulated pressure trace matches the measurement and the deviations in the gas exchange work is reduced by 40%. • Additionally, the model enables the prediction of the wastegate angle to improve the setup of engine control units.

Identifier

  • REPORT NUMBER: RWTH-2020-10177

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