Quantitative investigation on the spray mixture formation for ethanol-gasoline blends via UV–Vis dual-wavelength laser absorption scattering (LAS) technique

This study investigated spray mixture formation of ethanol-gasoline blends (E0, E85 and E100) under direct-injection spark ignition-like (DISI-like) condition in a constant volume vessel. An ultraviolet (UV) – visible (Vis) dual-wavelength laser absorption scattering (LAS) technique was used to quantitatively measure the liquid and vapor phase distributions. The toluene with the similar physical properties to gasoline and high absorption for ultraviolet, especially for a boiling point close to the distillation temperature of 50% mass, was employed to determine the gasoline distribution. Likewise, the ethanol distribution was determined by methyl ethyl ketone (MEK). The results show that E100 evaporates faster than E0 under high temperature condition. A similar temporal variation and level of liquid penetration length are observed for E0 and E100. In E85 spray, ethanol component has a faster evaporation than high boiling point (HBP) components in gasoline before end of injection (EOI). Meanwhile, the HBP component vapor mainly presents downstream the spray. Due to lower boiling point and higher vapor diffusivity, the ethanol component shows a larger dispersion at radial distance of the spray, as a result, it covers the inner HBP component vapor. Furthermore, the evaporation ratio of E85 increases higher than E100 at EOI and slightly after EOI, which is probably attributed to the azeotrope mixture yielded by ethanol and gasoline. This effect, however, remains insignificant until the EOI. In addition, the non-uniform distribution of blending fraction in E85 is clearly identified under different injection pressures. In the case of P_inj = 20 MPa, the dense HBP component vapor at tip region becomes significant. Meanwhile, the higher blending ratio of ethanol component presents a narrow region at spray periphery. The injection pressure shows less impacts on HBP component evaporation in E85. Whereas the evaporation of ethanol component remarkably decreases under a lower injection pressure.