Numerical simulation of fuel sprays in diesel engines

Kohei Fukuda


Engine simulations with diesel fuel spray at ultra-high injection pressures ranging from 100 to 300 MPa were conducted in a vertical valve engine geometry using ANSYS FLUENT 13.0. The in-cylinder flow was calculated by RANS models and DES and validated with the experimental data. The fuel spray characteristics such as Sauter mean diameter, spray cone angle, spray tip penetration and fuel/air mixture were studied under the presence of in-cylinder flow. The ultra-high injection pressures assist in the breakup of droplets into smaller size, accelerating atomization, dispersing the spray in a wide cone angle and mixing air/fuel effectively. However, the rate of change in droplet size was reduced by increasing the injection pressure. Also, high air density in the cylinder did not induce the breakup of droplets. The spray simulations failed for the RNG k-[varepsilon] and standard k-ω models and the issue was found to be the sensitivity to of the calculations to grid size and type in the particle tracking methodology.