An innovative losses model for efficiency map fitting of vaneless and variable vaned radial turbines extrapolating towards extreme off-design conditions

Abstract

[EN] Pulsating flow in automotive turbocharger turbines makes it necessary to know performance characteristics in difficult to measure off-design conditions. Physically based extrapolation models can be used to extrapolate towards unmeasured map regions. However, for model parameter fittings common maps have low numbers of measurement points per speedline available. Measurements with different variable geometry turbine (VGT) openings amplify the available data and help to characterize the turbine in a wider aerodynamic range. Nevertheless, physical models able to fit the data of several speeds and VGT positions with the same set of fitting parameters are rare. Thus, a model that is capable of fitting all speeds and VGT positions simultaneously and with the capability of extrapolating reliably towards low pressure ratios, unmeasured speeds, and VGT openings has been developed. The model is based on novel and commonly used loss correlations combined in an innovative way and has been validated in a wide range of pressure ratios towards extreme off-design conditions. By deactivating stator passage effects, the model can also extrapolate efficiency maps of vaneless turbines. The set of loss models is able to reproduce the measured data in a good quality for tested turbines with a very reduced number of fitting coefficients. (C) 2019 Elsevier Ltd. All rights reserved.