Spray Drop Size Distribution and Velocity Distribution issued from a Prefilming Airblast Atomizer

This work explore the possibility to determine the spray characteristics at early stage of the
atomization process. This approach has been firstly proposed in [7] propose to characterize
the liquid-gas surface in term of surface curvature distribution allowing the determination of
which part of the surface is already representative of the final spray. This innovative approach
is based on numerical simulation but could be extended in principle on experimental imagery
techniques for instance. In this work, the methodology is extended to include surface velocity
measurements to provide the joint distribution of the spray in term of diameter and velocity. The
configuration is representative of an aeronautic injector used in the European project CHAiRLIFT
and focus on the prefilming airblast atomization. Such an atomization process involves
a wide range of length scales. The diameter of the aeronautic atomizer could be three orders
of magnitude higher than the diameter of the smallest droplet. Therefore, performing a CFD
simulation is neither a straightforward nor a cheap process computationally speaking. Thus,
a workflow, which divides the atomizer in less complex processes, is presented in this work
to make the simulation affordable in an industrial perspective. The objective is to compute
the properties that determine the spray behavior for the following combustion process. The
OpenFOAM library is used to perform the simulation. In addition to the numerical strategy to
capture first steps of the atomization process the focus of our presentation will be on the post
processing of the simulation to extract the main features of the spray. The results presented
concern the drop size distribution of the spray and the joint velocity distributions of the droplets.
The post processing methodology is based on an analysis of the surface density joint distribution
for curvatures and velocity. We believe this methodology can be used to enrich the spray
injection models for further reactive spray flame simulations.