Advanced sub-model for airblast atomizers

A three-dimensional viscous stability analysis has been carried out to model airblast atomization. The model considers an annular liquid sheet downstream of an airblast atomizer and incorporates essential features, such as three-dimensional disturbances, liquid viscosity, inner and outer air swirl, and finite film thickness. Effects of axial velocity, sir swirl, and liquid viscosity on the growth rates of various disturbance modes have been examined in detail. It has been found that increasing the relative axial velocity between the liquid and the gas phases significantly improves the fuel atomization. The inner and outer air moving together enhances the instability of the liquid sheet more significantly than only the inner or outer air. When air swirl is absent, the axisymmetric mode dominates the breakup process of the liquid sheet. Liquid viscosity is found to have a twofold effect: reduce the growth rates of unstable waves and shift the dispersion diagram toward long waves. Air swirl not only promotes the instability of the liquid sheet, but also switches the dominant mode from the axisymmetric mode to a helical mode. A combination of the inner and outer air swirl improves airblast atomization more significantly than a single air swirl.