Numerical study on the atomization characteristics of diesel sprays from non-cylindrical nozzles

The combustion and emission performance of diesel engines largely depend on the in-cylinder fuel atomization quality, with injection pressure, ambient pressure, and nozzle geometry being key influencing factors. Recently, non-cylindrical nozzles have gained attention for their potential to promote jet breakup and improve atomization characteristics. To systematically investigate the effects of injection pressure and ambient pressure on the jet atomization characteristics of non-cylindrical nozzles, this study establishes a numerical model based on the Gerris platform, employing the Volume of Fluid (VOF) method and Adaptive Mesh Refinement (AMR). Simulations are conducted for four nozzle configurations: cylindrical, tapered, diverging, and elliptical. The variations of spray penetration distance and Sauter Mean Diameter (SMD) are examined under different injection pressures (80–160 MPa) and ambient pressures (0–12 MPa). Results show that increasing injection pressure increases spray penetration distance and decreases SMD. For example, at an ambient pressure of 3 MPa, when the injection pressure rises from 80 to 160 MPa, the spray penetration distance of the diverging nozzle increases from approximately 60 to 88 mm, while its SMD decreases from about 12.9 to 11.7 μm, similar trends are observed for the other nozzles. Increasing ambient pressure reduces spray penetration distance but enhances gas-liquid interaction, leading to a decrease in SMD and improved atomization quality. At a fixed injection pressure of 120 MPa, raising the ambient pressure from 0 to 12 MPa reduces the spray penetration distance of the tapered nozzle from about 54 to 51 mm and decreases its SMD from roughly 9.8 to 8.7 μm, similar trends are observed for the other nozzles. In conclusion, both injection pressure and ambient pressure significantly affect jet atomization from non-cylindrical nozzles, and proper selection of nozzle geometry can optimize atomization performance under different operating conditions.