In the paper, the unsteady behaviour of a turbocharger waste-gated turbine (IHI-RHF3) is investigated following both an experimental and numerical approach. First, an experimental campaign is performed in a specialized test rig operating at the University of Genoa, for different openings of the waste-gate valve and under steady and unsteady flow operations. A proper configuration of the turbine outlet circuit fitted with a separating wall is used to carry out instantaneous measurements downstream the turbine wheel and the waste-gate valve. The above data constitute the basis for the tuning and validation of a 1D turbine model, recently developed at the University of Naples. The procedure geometrically schematizes the entire turbine, starting from few linear and angular dimensions directly measured on the hardware. A preliminary model tuning is carried out on the basis of the characteristic map measured for a completely closed waste-gate valve under steady flow operations. Then, a refined 1D schematization of the experimental apparatus is implemented within the commercial GT-Power® software, including the turbine, the waste-gate circuit and the upstream and downstream measuring stations. In particular, the classical map-based approach is suitably corrected with a sequence of pipes that schematizes each component of the turbine (inlet/outlet ducts, volute and wheel) to account for the wave propagation and storage phenomena inside the machine. A detailed 1D schematization of the waste-gate circuit is also implemented and independently tuned. Finally, the turbine model capability under unsteady flow conditions is tested for different waste-gate openings and pulse frequencies, by applying time-dependent boundary conditions. In particular, the upstream and downstream measured pressure and temperature are imposed at the model ends, and the instantaneous mass flow rate and actual power are numerically evaluated. The results are compared with the experimental data, denoting a good accuracy, and showing some improvements with the respect to the standard turbine modelling in the case of the mass flow rate prediction. On the contrary, the computed actual power shows some inaccuracies, especially at higher pulse frequencies.
|Titolo:||One-dimensional simulations and experimental analysis of a wastegated turbine for automotive engines under unsteady flow conditions|
|Data di pubblicazione:||2015|
|Appare nelle tipologie:||01.01 - Articolo su rivista|
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|Proceedings of the Institution of Mechanical Engineers, Part D_ Journal of Automobile Engineering-2015-De Bellis-0954407015571672.pdf||Documento in versione editoriale||Administrator Richiedi una copia|