ANALYSIS OF UNSTEADY ENERGY FLUXES IN A TURBOCHARGER BY USING A HOLISTIC MODEL EXTRAPOLATING STANDARD LOOKUP TABLES IN FULL ENGINE OPERATING MAP

摘要

One dimensional modeling can give important insights into the needs of engine and turbocharger design. In this paper a holistic turbocharger model that calculates besides transient effects also heat transfer, friction losses, extrapolated adiabatic turbine and compressor maps has been validated over the range of an entire diesel engine map. Due to its capability of calculating heat fluxes in very different conditions turbocharger maps measured in hot as well as maps measured in cold conditions can be used as input data of the model. The turbocharger model has been validated in a high number of running conditions and has been compared against a reference model to highlight its advantages. Since the model can calculate data that are difficult to measure as complex internal turbocharger heat transfer, entropy, and adiabatic efficiency pulses, these numbers have been analyzed. It has been found out that the analyzed turbocharger loses relatively high amounts of heat especially at its highest efficiency zone. Further, the importance of the isentropic power during the valley in engine exhaust gas flow pulses has been highlighted. Apart from the peak energy a big part of isentropic energy is available in the valley of the pulse. Finally, a specific coefficient has been proposed to quantify the available energy rate in the valley of the pulse.