On the Measurement and Simulation of Flow-Acoustic Sound Propagation in Turbochargers

Hendrik Ruppert; Felix Falke; Stefan Pischinger; Marco Günther; Ralf Stienen

doi:10.4271/2019-01-1488

Most of today’s internal combustion engines are turbocharged by combined radial compressors and turbines for downsizing. This mostly leads to reduced orifice noise of both intake and exhaust systems, but the detailed damping mechanisms remain yet unknown. Intake and exhaust systems are developed with 1D-CFD simulations, but validated acoustic sub-models for turbochargers are not yet available. Therefore the aim of this publication is studying the turbocharger’s silencing capabilities and subsequently develop new acoustic turbocharger models.

The acoustic properties of the turbocharger can be well described by transmission loss. In addition to thermodynamic variations, parameter variations with wastegate and VTG systems were also performed. A total of four turbochargers of very different sizes were investigated. Low frequency attenuation is dominated by impedance discontinuities, increasing considerably with mass flow and pressure ratio. High frequency transmission loss is generated by destructive interferences in the stator, which depend on the stator mass flow distribution and the turbocharger size.

A new generic turbocharger model was developed to model both low frequency impedance discontinuities and high-frequency interferences by combining a generic geometric housing model with dynamically controlled energy terms and conventional turbocharger maps. The high thermodynamic quality is a necessary prerequisite for the high acoustic accuracy achieved. The model could be validated and the accuracy was increased by as much as 5 dB, especially for higher frequencies of engine noise.

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On the Measurement and Simulation of Flow-Acoustic Sound Propagation in Turbochargers 2019-01-1488

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