Investigation of the interaction mechanisms between closely spaced sprays from micro-hole nozzles
A computer code for the dispersed liquid phase is constructed in an Eulerian-Fluid-Lagrangian-Particle spray simulation program. Various sub-models for spray droplets, which include droplet injection, droplet tracking, inter-phase momentum coupling, droplet breakup, droplet collision and droplet turbulent dispersion, are implemented.
An adaptive meshing method for collision calculation in sprays is presented. The adaptive mesh is shown to be capable of producing higher spatial resolution than the conventional mesh. At the same time the mesh can maintain an adequate sample of computational parcels in each cell to ensure statistically accurate results. The random orientation of the mesh avoids any artifacts associated with a fixed mesh, leading to reduced grid dependency of collision calculation.
Satellite droplet formation resulting from ligament stretching during collision can significantly reduce the spray drop size. An existing satellite droplet formation model has been improved to reflect the experimental findings that the satellite droplets are much smaller than the parent droplets. The improved model is shown to produce better agreement with the experimental data.
Micro-hole nozzles of various configurations are simulated and the results are discussed. The possible interaction mechanisms between the closely spaced sprays are identified and their relative significance is assessed. It is found that the collisions between droplets from different holes are largely responsible for the droplet size variation with different nozzle configurations. The results obtained in this work are very important in facilitating the design and manufacturing of the micro-hole nozzles.