Modeling the spray characteristics of blended fuels for gasoline direct injection applications

Methanol and ethanol are considered as potential candidates for alternative fuels in spark-ignited engines and flex-fuel vehicles. Alcoholic fuels have higher latent heat of vaporization (h(fg)), lower boiling-point temperature and higher-octane numbers help the engine run under higher compression ratios, resulting in better efficiency and fuel economy. A numerical study is carried out to understand the spray-breakup and vaporization characteristics of binary blended fuel and ternary fuel blend compared to single-component fuel for gasoline direct injection (GDI) system. Multiple simulations were carried out by substituting individual fuel properties of isooctane with those of ethanol to understand the relative importance and effect of fuel properties on spray characteristics. The spray characteristics of pure isooctane fuel and their blends with ethanol and methanol are studied and compared, and the charge cooling effects for alcoholic fuels have been observed. The Spray G operating condition has been taken from the Engine Combustion Network (ECN) for this study. The simulated data for isooctane has been validated with the experimental data from the ECN, and a similar model setup has been used for pure and blended fuel sprays. The discrete-phase modeling (DPM) approach is carried out, and the Unsteady Reynolds-Averaged Navier-Stokes (URANS) RNG (Renormalization) k-E turbulence model is considered in understanding the spray characterization. The blended methanol fuels have higher penetration lengths compared with ethanol ones. The penetration of the blended fuels (binary and ternary) is slightly lower than the isooctane. The ternary blends showed spray characteristics similar to those of E85, and it indicates that the ternary blended fuel has the potential to be used as a drop-in fuel for a GDI-based flex-fuel vehicle.