Mixture formation analysis of an opposed-piston two-stroke gasoline-direct-injection engine

The effects of different flow forms on an opposed-piston two-stroke (OPTS) gasoline-direct-injection (GDI) engine was studied by analyzing the mixture formation and combustion. Swirl was broken and dissipated gradually and the turbulence kinetic energy (TKE) was small in the compression process; however, tumble was strengthened and the TKE was strong in the compression process. For swirl around X axis (the axis of cylinder) and tumble around Y axis (the vertical direction of injector), droplets were attached to the cylinder liner by the centrifugal force and the mixture distribution was poor. For tumble around Z axis (the direction of injector), the wall film in cylinder liner was thin and mixture distribution was homogeneous. Results showed that since the injector were installed on the wall of the cylinder liner in the OPTS-GDI engine, the spray angle was small and the mixture formation time was short. The 45° oblique axis tumble ratio of 1 was reasonable for the mixture formation and combustion for an OPTS-GDI engine.