Spray-evaporation characteristics of n-pentanol/n-dodecane binary fuel at ultra-high injection pressure

Abstract

The spray and evaporation characteristics of the fuel directly affect the combustion and emission performance of the engine. In this work, the atomization and evaporation characteristics of the n-pentanol/n-dodecane binary fuel were investigated by varying the injection pressure (100–300 MPa). Process of breaking, atomization, evaporation and oil-gas mixing were measured by schlieren technique. The liquid phase length of the spray was measured using the Mie scattering method. Numerical simulations were performed in a constant volume combustion chamber to further investigate the effects of injection pressure. The findings demonstrate that n-pentanol/n-dodecane binary fuel has slightly more liquid penetration than pure n-dodecane fuel, which may be attributed to n-pentanol's higher density. The results also show that the ultra-high injection pressure notably improved the spray penetration and reduced the droplet size that led to fragmentation of the fuel droplets and effectively improved the atomization characteristics. Moreover, a substantial reduction of over 20% in droplet size was observed with the increase in injection pressure from 100 to 200 MPa. However, it has been observed that the reduction in droplet size due to an increase in injection pressure diminishes when the pressure exceeds 200 MPa. In such cases, the size reduction is less than 10%, which implies that the impact of ultra-high injection pressure on size reduction is restricted. Although the impact of ultra-high injection pressure on fuel evaporation under evaporative conditions is limited, it can enhance fuel air mixing performance through intensified turbulence activity within the spray, thereby promoting greater air roll-up.