Numerical investigation of stratified air/fuel preparation in a GDI engine

• CFD simulations of fuel spray and mixing under GDI conditions.
• Effects of ambient and fuel conditions on fuel atomization is studied.
• Late injection strategy investigated for part load conditions.
• Engine operating conditions affected equivalence ratio near spark plug.

A numerical study has been performed to study atomization and preparation of air/fuel mixture under Gasoline Direct Injection (GDI) conditions. Performance of a single-hole injector was initially investigated and effects of ambient pressure, temperature and temperature of the injected fuel on liquid and vapour penetration lengths were analysed. Subsequently, air/fuel mixture preparation for a multi-hole injector in a simplified GDI engine was investigated. To simulate part load engine conditions, fuel spray and mixing was studied during the compression stroke of the engine. Effect of charge stratification, wall wettability and droplet statics on engine operating conditions like start of injection, injection pulse width, charge inlet temperature, engine RPM and overall equivalence ratio was studied. The droplet phase was tracked using Lagrangian framework and the continuous phase was simulated within the Eulerian framework. Turbulence modelling was performed using the standard k − ε model and ideal gas law was assumed while performing vapour-liquid equilibrium calculations.