Determination of the Realistic Turbocharger Efficiency With Pulsating Gas-Flow Compared on a 4-Cylinder Engine PUBLIC ACCESS

[+] Author Affiliations
Ferdinand Trenc, Matej Čer, Frančišek Bizjan

University of Ljubljana, Ljubljana, Slovenia

Aleš Hribernik

University of Maribor, Maribor, Slovenia

Paper No. 98-GT-358, pp. V002T04A005; 5 pages
  • ASME 1998 International Gas Turbine and Aeroengine Congress and Exhibition
  • Volume 2: Aircraft Engine; Marine; Microturbines and Small Turbomachinery
  • Stockholm, Sweden, June 2–5, 1998
  • Conference Sponsors: International Gas Turbine Institute
  • ISBN: 978-0-7918-7863-7
  • Copyright © 1998 by ASME


Small single or twin entry radial turbines are mostly used to drive compressors of the turbocharged internal combustion engines. There are two general possibilities to feed the turbine of a four-stroke, 4-cylinder turbocharged Diesel engine: 1) by preserving most of the available exhaust kinetic energy, or 2) by mixing exhaust pulses from all cylinders in one common manifold. In the first case, better utilization of the dynamic pulse energy increases efficiency of the turbine; highly unsteady mass flow of the exhaust gasses, on the other hand, and thus periods of partial exhaust flow admission at the turbine inlet simultaneously reduces this gain in the turbine efficiency. More steady mass-flow of the exhaust gasses is created in the case of the exhaust system 2), however some kinetic energy is lost during the mixing phase in the common exhaust manifold. Calculation of the overall turbocharger and turbine efficiency is normally based on average values of the measured pressures and temperatures. As the result apparent efficiencies are obtained; the more the flow is pulsating, the bigger is the difference between the real and the apparent efficiency. The ratio between these two efficiencies is known as the energy pulsation factor β. It depends generally on the “pulse intensity”-pressure deviation from its mean value, shape of the pressure pulse, number of the individual pulses feeding separate gas turbine inlets, turbocharger, and can be successfully used to determine real efficiency of a turbocharger and to define some working parameters of the engine.

A field of β factors for different engine running conditions and for the 4-cylinder engine with 2-cylinder group pulse system (rarely applied), and the commonly applied exhaust system with 4-cylinder group and moderate pressure fluctuation is presented in the paper. Influence of the dynamic exhaust temperatures on the β value is discussed as well.

Copyright © 1998 by ASME
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