Weakly nonlinear instability of an annular liquid sheet subjected to unequal inner and outer gas streams

Instability and breakup of annular liquid sheet are encountered in fuel injectors used in gas turbine engines. A weakly nonlinear stability analysis has been carried out for annular liquid fuel sheet subjected to unequal inner and outer gas velocities by a perturbation expansion technique with the initial amplitude of the disturbance as the perturbation parameter. The liquid sheet is considered to move at a uniform axial velocity and is subjected to inner and outer gas streams of differing axial velocities. The breakup length is calculated, and the effect of the various flow parameters is investigated. It is found that the break-up length is reduced by an increase in the liquid velocity and the gas velocities. The inner air stream is more effective in disintegrating the sheet than the outer air stream.