Characteristics of radial inward-turbines for exhaust gas turbochargers under nonsteady flow conditions. Effects of waveforms on prediction of turbine performance.

Abstract

This paper deals with effects of waveforms on predicting performances of a radial turbine for turbochargers under pulsating flows. The extensive unsteady tests were conducted with several pulse shapes and pressure amplitudes over a pulse frequency range from 10 to 70 Hz produced by a disk-type pulse generator rig. Five kinds of pulse shapes were simulated for exhaust gas flows from diesel engines. The time-mean method and the quasi-steady flow analysis were carried out to predict the turbine characteristics by using the steady flow turbine performance. As the results, the following points are made clear. For most turbine running conditions, the quasi-steady flow analysis is satisfactorily valid regardless of whether the turbine is effected by the waveform, amplitude and frequency. It is considered that the turbine under pulsating flow conditions works along the curves of steady flow performances except for windage states. The time-mean method predicts the power output fairly well, but grossly overestimates the mass flow rates according to the waveforms.