Advanced sub-model for airblast atomizers

A three-dimensional viscous stability analysis has been carried out to mode l airblast atomization. The model considers an annular liquid sheet downstr eam of an airblast atomizer and incorporates essential features, such as th ree-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 exami ned in detail. It has been found that increasing the relative axial velocit y between the liquid and the gas phases significantly improves the fuel ato mization. The inner and outer air moving together enhances the instability of the liquid sheet more significantly than only the inner or outer air. Wh en air swirl is absent, the axisymmetric mode dominates the breakup process of the liquid sheet. Liquid viscosity is found to have a twofold effect: r educe the growth rates of unstable waves and shift the dispersion diagram t oward 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 airb last atomization more significantly than a single air swirl.