A Numerical Study on the Effects of FAME Blends on Diesel Spray and Soot Formation by Using KIVA3V Code Including Detailed Kinetics and Phenomenological Soot Formation Models

摘要

The objective of the present research was to analyze the effects of using oxygenated fuels (FAMEs or biodiesel fuels) on injected fuel spray and soot formation. A 3-D numerical study which using the KIVA-3V code with modified chemical and physical models was conducted. The large-eddy simulation (LES) model and KH-RT model were used to simulate fuel spray characteristics. To predict soot formation processes, a model for predicting gas-phase polycyclic aromatic hydrocarbons (PAHs) precursor formation was coupled with a detailed phenomenological particle formation model that included soot nucleation from the precursors, surface growth/oxidation and particle coagulation. The calculated liquid spray penetration results for all fuels agreed well with the measured data. The spray measurements were conducted using a constant volume chamber (CVC), which can simulate the ambient temperature and density under real engine conditions. The numerical results suggest that the liquid penetration length with methyl oleate (MO) tested as a representative of FAMEs, is longer than with diesel fuel, D100 and tends to decrease as the injection pressure is increased for all fuels. In addition, the results show that the ignition delay is shorter while flame temperatures are lower with MO than with D100. With D100, a soot formation phase was observed near the injection nozzle, and soot formation was observed along the contour of the flame. In contrast, early phase soot formation was not observed with MO because oxygen in the fuel plays an important role in reducing the associated reactions and combustion temperatures.