Numerical and Experimental Study of Stratified Turbulent Combustion in a Spray-Guided Gasoline Direct Injection Engine

Abstract

Direct Injection (DI) of gasoline into cylinder of a Spark Ignition (SI) engine is widely recognized to be a promising technology capable for significantly reducing fuel consumption and carbon dioxide emissions as compared to a port-fuel injection SI engine. In particular, spray-guided (SG) GDI combustion systems allow for further improvement in fuel efficiency. Moreover, efficient CFD tools for numerical simulations of spray and combustion processes have been becoming increasingly important in engine development. In previous papers, a so-called Flame Speed Closure (FSC) model was implemented into an open source code OpenFOAM ® with the capability of addressing important phenomena in SG GDI engines, e.g. fluctuations in mixture composition and the proper evaluation of combustion temperature for the products. In this paper, the aforementioned FSC model is applied to investigate the stratified turbulent combustion in a SG GDI engine in the frame work of unsteady 3D Reynolds-Averaged Navier-Stokes (RANS) simulations. The computed results are compared with the measured pressure traces obtained in the same research group for both low and medium load conditions. Further on, the calculated Reynolds-averaged progress variable is compared to the experimentally observed images.