The Numerical Simulation of the Atomization of a Kerosene Film in an Air-Assist Atomizer with a Prefilmer

Using the volume of fluid (VOF) method in the approximation of 2D axisymmetric swirling flow, the primary atomization of a kerosene film in an air-assist centrifugal atomizer of an aircraft engine operating in cruise mode has been studied. The evolution of the system is simulated using Reynolds-averaged nonstationary equations of viscous fluid flow on meshes with different cell sizes (0.78125, 1.5625, 3.125, and 6.25 µm); mesh convergence was achieved at 1.5625 μm. Kelvin–Helmholtz instability, which causes waves on the surface of the fuel film, was revealed. After the detachment of the film from the prefilmer edge, the thinning of the film near the trough of the wave leads to its breakup at this location. This film atomization regime is consistent with one of the regimes revealed in an air-assist atomizer operating under standard conditions in a combustion chamber. A specific feature of this regime is that some fuel ligaments formed as a result of the atomization are thrown radially into the stagnant zone. As a result, two spray cones appear in the atomizer. It should be noted that in a 2D axisymmetric formulation only the primary atomization can be analyzed, correctly, but not the subsequent formation from the fuel ligaments of droplets of complex shape close to spherical. Interest in the problem of the atomization of the fuel film in air-assist atomizers during the operation of the aircraft engine in cruise mode is due to the lack of information about this process, both numerical and experimental.