EXPERIMENTAL EXAMINATION OF EXHAUST GAS TURBINE FOR TURBO-CHARGER IN UNSTEADY (PULSATING) OPERATION

Abstract

In this paper the impact losses on the inward part of the rotary bladed wheel of the tur- bine in turbo-chargers and the subsequent decrease in the turbine efficiency were examined by the authors. The essence of their experiments was to establish an unsteady (pulsating) state of operation with the no-load turbo-charger by an electric engine operated rotary-valve installed immediately ahead of the turbine in the inlet duct. During the experiments the amplitude and frequency of the pressure change in the pulsating gas flow could be altered. Certain parameters of the pulsating gas flow and the correlation between the flow and the impaired efficiency of the turbine in pulsating state of operation were examined. Authors were led to the conclusion that the turbine efficiency is impaired due to the pulse of the gas flow. This impaired turbine efficiency was most considerably affected by the amplitude of the pulsating gas flow while frequency of pulse, and a hardly measurable change in efficiency was brought about due to the change in turbine speed. During the experiments the maximum decrease in turbine efficiency was 4.% when the rate of pulse of the gas flow entering the turbine was: ~Jp (Pmax Pmin)' 2 P3 = (Prna-:: 0.5 During our experiments this was the maximum rate of pulse implemented in the gas flow.