BREAKUP OF ANNULAR VISCOUS-LIQUID JETS IN 2 GAS STREAMS

Linear stability theory is applied to study the breakup process of an annular viscous liquid jet exposed to both inner and outer gas streams of unequal velocities. The absolute liquid and gas velocities are con sidered in this temporal instability analysis. It is round that not on ly the velocity difference across each interface, but also the absolut e velocity of each fluid is important for the jet instability, althoug h the effect of absolute velocity is secondary compared with that of r elative velocity. A high-velocity coflowing gas stream is found to sig nificantly-improve atomization performance, A high-velocity gas inside of the annular liquid jet promotes the jet breakup process more than the gas of equivalent velocity outside of the jet. For equal liquid an d gas velocities, surface tension, liquid, and gas density exhibit eff ects on wave growth rates different from those when a velocity discont inuity is present across interfaces. However, the viscous damping effe ct on jet instability always exists for the cases with and without vel ocity differences at high Weber numbers. The liquid inertia, density r atio, and high gas velocity all contribute to better atomization perfo rmance, whereas surface tension and liquid viscosity increase the resu lting droplet size.