Numerical Modelling of Liquid Jet Breakup by Different Liquid Jet/Air Flow Orientations Using the Level Set Method

摘要

This paper presents the numerical results obtained from the numerical simulation of turbulent liquid jet atomization due to three distinctly different types of liquid jets/air orientations; namely, coflow jet, coaxial jet and the combined coflow-coaxial jet. The applied numerical method, developed by the present authors, is based on the solution of the Reynolds-Averaged Navier Stokes (RANS) equations for time-dependent, axisymmetric and incompressible two-phase flow in both phases separately and on regular and structured cell-centered collocated grids using the control volume approach. The transition from one phase to another is performed through a consistent balance of the interfacial dynamic and kinematic conditions. The topological interfacial changes as well as the geometrical quantities of the interface are predicted by applying the level set method. The results show the formation of the ligaments and its breakup into droplets with different sizes are greatly affected with the liquid/air orientation. The proposed combined coflow/coaxial orientation gives the best spray characteristics represented in final fine droplets. In general, the developed numerical method showed a remarkable capability to predict the primary breakup of the liquid jet. The rational preliminary results obtained give the possibility to extend the performed numerical simulation to predict the secondary atomization regime of the coaxial liquid jet under different operating conditions.