A holistic methodology to correct heat transfer and bearing friction losses from hot turbocharger maps in order to obtain adiabatic efficiency of the turbomachinery

Abstract

Turbocharger performance maps provided by manufacturers are usually far from the assumption of reproducing the isentropic performance. The reason being, those maps are usually measured using a hot gas stand. The definition of the effective turbocharger efficiency maps include the mechanical losses and heat transfer that has occurred during the gas stand test for the turbine maps and only the heat transfer for the compressor maps. Thus, a turbocharger engine model that uses these maps provides accurate results only when simulating turbocharger operative conditions similar to those at which the maps are recorded. However, for some critical situations such as Worldwide harmonized Light vehicles Test Cycles (WLTC) driving cycle or off-design conditions, it is difficult to ensure this assumption. In this article, an internal and external heat transfer model combined with mechanical losses model, both previously developed and calibrated, has been used as an original tool to ascertain a calculation procedure to obtain adiabatic maps from diabatic standard turbocharger maps. The turbocharger working operative conditions at the time of map measurements and geometrical information of the turbocharger are necessary to discount both effects precisely. However, the maps from turbocharger manufacturers do not include all required information. These create additional challenges to develop the procedure to obtain approximated adiabatic maps making some assumptions based on SAE standards for non-available data. A sensitivity study has been included in this article to check the validity of the hypothesis proposed by changing the values of parameters which are not included in the map data. The proposed procedure becomes a valuable tool either for Original Equipment Manufacturers (OEMs) to parameterize turbocharger performance accurately for benchmarking and turbocharged engine design or to turbocharger manufacturers to provide much-appreciated information of their performance maps.