Comparative study on the spray and combustion characteristics between diesel and kerosene underlow-temperature combustion (LTC)mode conditions

Abstract

Kerosene, an intermediate component of wide distillation fuel, has drawn increasing attention for low-temperature combustion mode due to its compromise of evaporation and ignition characteristics between diesel and gasoline. This study focuses on the comparison of spray and combustion characteristics between diesel and kerosene under low-temperature combustion mode conditions based on visualization tests in a constant volume chamber. Different injection pressures, ambient temperatures, and oxygen concentrations were tested at a constant ambient density of 16.67 kg/m3. The image processing results reveal that the liquid penetration distance of kerosene shows a maximum reduction of 33.5% compared to diesel with a smaller cone angle and spray area at 160 MPa and 800 K. At the same time, the ignition delay of kerosene is 0.9 ms longer than that of diesel, and the injection and combustion processes of kerosene are separated, making it much more similar to the premixed combustion. An increase in injection pressure improves the spray penetration distance but exerts little influence on the flame lift-off length and ignition delay for both fuels. Kerosene presents a lower spatially integrating natural luminosity, especially at low injection pressure. The liquid spray penetration distance and the ignition delay of kerosene are more sensitive to the increase in ambient temperature. However, the higher ambient temperature presents a greater effect on the SINL of diesel. With the decrease of ambient oxygen concentration, the ignition delay, flame lift-off length, spatially integrating natural luminosity, and soot oxidation rate of both fuels decrease obviously. Especially at 15 vol.% ambient oxygen, kerosene presents a much weaker luminosity. These results imply that kerosene exhibits a very similar trend to diesel in terms of spray and combustion characteristics. Moreover, kerosene has a stronger potential to reduce soot formation than diesel with a better fuel-air mixing process under low-temperature combustion mode conditions.