Effect of fuel spray inclinations on spray characteristics in a port fuel injected engine - A CFD study

In order to achieve good fuel spray characteristics, proper placing of the fuel injector in the intake manifold in port fuel injected (PFI) gasoline engines is very crucial. In automotive PFI engines, vehicle layout may be a constraint to mount the fuel injector in best possible location and inclination. In general, PFI engines use straight spray fuel injection. However, if there is a vehicle layout constraint, then inclined fuel spray may be suitable which is not very common. Hence, it is important to understand the effect of fuel spray inclination on fuel spray characteristics. In this study, a CFD analysis has been carried out for the four inclinations of fuel spray and the results are compared. The geometrical modeling of the fuel injector is done using ProE software. It is meshed with polyhedral cells and mesh refinement is done wherever required. Inlet air velocity and exit pressure of intake pipe at wide-open-throttle conditions are used as boundary conditions. In this study, droplet size distribution, sauter mean diameter (SMD), fuel penetration and evaporation rate are analyzed. Also available actual mass flow rate of the fuel injector with straight fuel spray are compared with numerical predictions. From the analysis of the results, it is found that straight fuel spray is preferable in terms of good fuel spray characteristics. However, if vehicle layout does not permit it, then 5° inclined spray may be used, without compromising much on fuel spray characteristics. © 2013 SAE International.