Calculation Accuracy of Pulsating Flow through the Turbine of SI-Engine Turbochargers - Part 1 Calculations for Choice of Turbines with Different Flow Characteristics

Abstract

The paper treats pulsating flow through the turbine of SI-engine turbochargers. In engine design, 1D engine-simulations are very convenient tools for optimization and concept studies. However, they have drawbacks in certain areas. The accuracy, when predicting turbocharger turbine power, is lower than desired. The reason for that is a lack of knowledge about the phenomenon of pulsating flow through the turbine. The background to the problem is described in the paper. This investigation aims at learning more about this unsteady, pulsating flow, on the engine. The method used is to do large parameter changes to several parameters in turbine and manifold designs such as A/R and trim in the turbine and also volume and length of the exhaust manifold. For selection of A/R and trim, as well as an aid in the analysis of measured data, the meanline turbine design software Rital from Concepts NREC [1] was used. Three different turbines were investigated, all with the same mass flow capacity. The three different manifolds were designed to alter the pulsation shape at the turbine inlet. The calculation results show, that through these large parameter changes, it is possible to significantly alter the conditions at both the turbine inlet (shape of pressure and massflow curves) and at the turbine wheel inlet (flow angle and velocity). This has a significant impact on the performance of the turbine and engine.