Generalized Liquid Film Atomization Theory

The increase of the fuel burning area required by most practical combustion processes in order to guarantee the minimum energy density rate release for their start up and operation is normally achieved by the proper choice among several existing types of atomizers. For instance, impinging and multi-impinging jets atomizers are used in rocket combustion chambers, while splash-plate atomizers find their use when wall film cooling is required. Pressure swirl atomizers, either of simplex or duplex kind, along with Y-Jet or Spider Jet atomizers are used in industrial applications and in turbine combustion chambers. Notice, however, that all the types of atomizing devices listed above have one point in common: they are of pre-filming kind, i.e., before the droplet spray is generated, a liquid film is formed. This liquid film is broken into unstable ligaments which contract under the action of surface tension forming the droplets. Once the film thickness is estimated, the droplets’ SMD (Sauter Mean Diameter) can be calculated, yielding a crucial parameter for the combustion chamber design. However, although this mechanism of droplet formation has been under study for several decades, most of the available results, are based upon experimental data, valid for a special type of atomizer under the given specific conditions only. This work offers a generalized theory for theoretically estimating the SMD of sprays generated by liquid pre-filming atomizers in general.