Browse Publications Technical Papers 2005-01-3812
2005-10-24

Calculation Accuracy of Pulsating Flow through the Turbine of SI-engine Turbochargers - Part 2 Measurements, Simulation Correlations and Conclusions 2005-01-3812

This paper is a continuation of SAE-Paper 2005-01-0222 presented at the 2005 SAE World Congress, denoted Part 1 in this text. In Part 1 three turbines were selected from calculations and three manifolds with different geometries were designed. This paper, Part 2, covers the results from engine-simulations and measurements on these nine different combinations of turbines and manifolds. It was shown that the possibility of maintaining isentropic power was the most important property, overshadowing any differences in turbine efficiency. The isentropic power was inversely dependent on both manifold volume and turbine throat area.
The GT-Power models of all nine setups were calibrated against the measured data. The need for efficiency and massflow multipliers is described. The efficiency multiplier depended on mass flow through the turbine, with a distinct minimum value (0.7-0.8) around 0.03 kg/s and higher around that. The efficiency multiplier could not be shown to depend on pulsation amplitude of the turbine inlet flow. The mass flow multiplier was almost linear with engine speed.
The on-engine turbine efficiency was calculated from a combination of measured and simulated data. Different approaches for this calculation were tested, among which also mass storage was included. The chosen method used equal massflow in and out from the turbine at every instant and a floating average over 30 CAD.
To enable explanation of the different behaviors on the engine, detailed measurements were conducted on the three turbines in a steady-state turbine flow rig. These measurements were used to calibrate separate turbine simulation models in the software Rital, which were used to describe the internal flow of the turbines.
The three methods of estimating the on-engine turbine efficiency were compared. GT-Power and Rital showed similar trends for the efficiency, but the on-engine measured efficiency gave lower values for the first, most energetic, part of the exhaust pulse.
Furthermore, the three manifold types were analyzed and the benefits from each of them sorted out.

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