Effect of Flowfield Non-Uniformities on Emissions Predictions in HSDI Engines
The role of the fluid motion in a diesel engine on mixing and combustion was investigated using the CFD code Kiva-3v. The study considered pre-mixed charge compression ignition (PCCI) combustion that is a hybrid combustion system characterized by early injection timings and high amounts of EGR dilution to delay the start and lower the temperature of combustion. The fuel oxidizer mixture is not homogeneous at the start of combustion and therefore requires further mixing for complete combustion. PCCI combustion systems are characterized by relatively high CO and UHC emissions. This work investigates attenuating CO emissions by enhancing mixing processes through non-uniform flowfield motions. The fluid motion was characterized by the amount of average angular rotation about the cylindrical axis (swirl ratio) and the amount of non-uniform motion imparted by the relative amounts of mass inducted through tangential and helical intake ports in a 0.5L HSDI diesel engine.