Effect of Fuel Injection Spray Angle on NOx and Soot Emission in CI Engine Using Unsteady Flamelet Model

Abstract

Effect of piston wall wetting due to misalignment in fuel injection on NOx and soot emissions were estimated using 3D CFD modelling in a CI engine with compression ratio of 18. Eulerian- Lagrangian approach was used in this study where the time history of fuel spray and atomization was modeled in the Lagrangian framework whereas in-cylinder aerodynamics was modeled by solving the 3D Navier Stokes equation in the Eulerian framework. Turbulence was modeled using k-ɛ model. A 6-hole fuel injector was used in this work and only 1/6th sector of the engine volume was modeled assuming uniform fuel injection. Combustion was modelled using by using 246 species and 1062 reactions containing skeletal n-dodecane/n-butanol/NOx/Polycyclic Aromatic Hydrocarbon (PAH) combustion mechanism that was previously developed and reported in open literature (Wakale, Banerjee and Banerjee, 2020). Two fuel injection pressures of 800 bars and 1500 bars and three different fuel spray cone angles of 800, 1200 and 1590 were modeled. It was found that lower spray cone angle increases the propensity of soot formation at lower injection pressure. However, it was found that soot formation is not significantly affected by wall wetting and higher injection pressure.