A Procedure to Achieve 1D Predictive Modeling of Turbochargers under Hot and Pulsating Flow Conditions at the Turbine Inlet

Nowadays turbocharging the internal combustion engine has become an essential tool in the automotive industry to meet downsizing technique requirements. In that context turbocharger unsteadiness is huge since both turbine and compressor work under high pulsating flow conditions, being turbocharger behavior prediction more difficult but still key for matching and predicting ICE performance. The well understanding and modeling of the occurring physical phenomena during turbocharger unsteady and off-design operation seems crucial.

In this paper three small radial turbines used in turbochargers from passenger car applications have been tested under high temperature and pulsating flow conditions on the turbine side. A gas stand and a rotary valve installed on the turbine inlet have been used to reproduce pulses with desired characteristics. A beam-forming technique for pressure wave's decomposition has been used to analyze turbine performance in detail.

In order to analyze complex problem of hot pulsating flow on the turbine side, the experiments have been modeled using the 1-D gas-dynamic code OpenWAM™. Several turbocharger sub-models accounting for heat transfer and mechanical losses have been used instantaneously in a quasi-steady way. Besides a turbine geometrical model and an extrapolation methodology to extend turbine adiabatic maps have been applied in order to account for instantaneous efficiency variations and acoustical effects. It has been demonstrated how turbocharger proposed models can be used to well reproduce turbocharger performance working under hot pulsating flow conditions. Accurate results predicting turbocharger averaged parameters and turbine instantaneous performance in both time and frequency domain have been obtained.