Keiji Konishi

Characteristics of Radial Inward Turbines for Exhaust Gas Turbochargers under Unsteady Flow Conditions. Unsteady Turbine Performance by High Temperature Working Gas.

This paper describes some important results obtained through experiments on a small inward radial gas turbine driven by high temperature pulsating flows. The temperature ranges from atmospheric temperature to 800 K. The waveforms of pulsation were nearly sinusoidal and had various pressure amplitude but fixed frequency (50 Hz). A newly designed reduction device, which consists of planetary gears, helped the turbine to work as nearly as in realistic circumstances. Main results are as follows. Even under the high temperature conditions, the turbine characteristics, such as the mass flow rate and the power output, are the same as those under the low temperature pulsating flow conditions as far as the estimations are performed by using ordinary corrected values taking the temperature into consideration. As to the effect of pulsation, the more the amplitude of pressure increase, the less the mass flow rate through the turbine became at the same expansion ratio. Adding these results, the windage states characteristics of the turbine were made clear through experiments.

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

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.