Spray and evaporation characteristics of n-pentanol-diesel blends in a constant volume chamber

Due to its excellent physicochemical property and renewable characters, pentanol is considered to be one of the most promising alternative biofuels applying to mobile vehicles. The objective of this study is to reveal the effects of pentanol addition to diesel in different ratios (0%, 20%, and 40% in volume) on the spray and evaporation characteristics under various injection and ambient conditions. The experiments were conducted in a premixed combustion heated constant volume combustion chamber with two different optical arrangements, high-speed schlieren technique and diffused back-illumination technique. The result shows pure diesel has a longer spray tip penetration and a smaller cone angle compared to pentanol blends under non-vaporizing conditions. With the increasing of ambient density, the difference of penetration characteristic between each blend becomes negligible but the gap of spray angle is still distinct. Compared to non-vaporizing condition, there is a downward trend for spray tip penetration of pure diesel under high temperature above 800 K while an increase trend for pentanol blends. The spray cone angles are unaffected by ambient temperature except increasing the blend ratio of pentanol to 40%. Air entrainment analysis such as spray volume and fuel equivalence ratio distribution were obtained by measured and model predicted respectively. The result shows pure diesel has a poor air-fuel mixing compared to pentanol blends. It also warned that the risk of liquid impingement on the wall becomes higher when the pentanol blend ratio reaches 40% at low temperature combustion conditions.