High Speed Imaging Study on the Spray Characteristics of Dieseline at Elevated Temperatures and Back Pressures

Dieseline combustion as a concept combines the advantages of gasoline and diesel by offline or online blending the two fuels. Dieseline has become an attractive new compression ignition combustion concept in recent years and furthermore an approach to a full-boiling-range fuel. High speed imaging with near-parallel backlit light was used to investigate the spray characteristics of dieseline and pure fuels with a common rail diesel injection system in a constant volume vessel. The results were acquired at different blend ratios, and at different temperatures and back pressures at an injection pressure of 100MPa. The penetrations and the evaporation states were compared with those of gasoline and diesel. The spray profile was analyzed in both area and shape with statistical methods. The effect of gasoline percentage on the evaporation in the fuel spray was evaluated. The blend ratio shows large impacts particularly in liquid phase area, on the liquid core length and the gas-to-liquid ratio (by area) at higher temperatures. It was found that the liquid phase areas and liquid core lengths produce a profile with relatively stable values in the late stage at 700 K and 820 K. A higher temperature or a higher gasoline percentage can advance the turning point time to the stable value. The atmospheric gas density mainly affects the penetration and propagation speed and has a minor impact on the gas-to-liquid ratio.