Mean-Line Modelling of a Variable Geometry Turbocharger (VGT) and Prediction of the Engine-Turbocharger Coupled Performance

Abstract

Mean-line modelling approach which has generally been applied to fixed geometry turbocharger turbines has been extended to predict the performance of the variable geometry turbine for different inlet blade angles. The model uses an initial assumption of turbine inlet pressure which was iteratively corrected based on outlet pressure boundary condition. The model was implemented in MATLAB and stable and convergent solutions were obtained using relaxation techniques for different operating conditions. Experiments were done on a state of the art transient diesel engine test bed using the same VGT turbine in the turbocharger at different engine torques and speeds. Using experimental data the model was calibrated for the aerodynamic blockage in the fixed nozzle and rotor blade passages. Results revealed that turbine overall pressure ratio can be predicted accurately if a blockage factor varying with nozzle blade orientation is used in the model.

Numerical Simulation of Two-Stage Variable Geometry Turbine

“…The preliminary analytical approach for the design of a VTG turbocharger is a necessity. A mean-line design approach is used to predict main geometry turbine features [1][2][3]. This is a quick and reliable method that predicts turbine performance at the mean-line height of the turbine blades.…”