Investigation On The Breakup Mechanism Of The Liquid Jet Under Longitudinal Disturbance

The research on breakup mechanism of the liquid jet is not only a traditional fluid mechanics problem,but also a topic with great theoretical res earch value and engineering application background.However,up to now the breakup mechanism of the liquid jet has not yet been well understood.In the present work,an investigation using the method of theory and experiment has been conducted on the break up of a free liquid jet and a liquid jet subject to disturbance.In this paper,combined with the basic fluid mechanics equations,the dispersion equations of Rayleigh and Weber have been deduced respectively.The mathematical expressions of the maximum disturbance growth rate and the optimum disturbance wavelength also have been obtained.A liquid jet experimental system mainly consisting of liquid jet driving system,exciting system and photographing system has been designed and established.A longitudinal vibration produced by the vibration exciter applied on the nozzle,and the effects of vibration frequency and vibration amplitude on the breakup of the liquid jet were investigated.The experimental analysis of free liquid jet shows that there are three modes of interaction between the main droplet and the satellite droplet: satellite merging with rear main droplet;no merging condition;satellite colliding with rear main droplet,and then merging with forward main droplet.The liquid jet has different forms of surface wave under different liquid jet velocity.In the low range of jet velocity,the breakup length of the liquid jet increases linearly with the increase of jet velocity,and as the decreases of nozzle diameter,the slope of the increase of breakup length decreases.In addition,the smaller the nozzle diameter,the wider range of the jet velocity where the breakup length increases linearly.Comparing with the breakup of free liquid jet,the breakup of the liquid jet subject to disturbance has the characteristics of periodicity and repeatability.The breakup length decreases with the increase of vibration amplitude.When the vibration frequency increases,the breakup length first increases and then decreases.what's more,the value of the vibration frequency under which the breakup length is the most shortest is equal to the value of the optimum frequency.The mode of the formation of droplet is different under different wavelength.This paper summarizes three modes: short-wavelength breakup mode(?/d<5),medium-wavelength breakup mode(5.0 < ?/d < 11.1),long-wavelength breakup mode(?/d>11.1).At the appropriate range of frequency and jet velocity,uniform droplets can be produced.With the increase of the nozzle diameter,both the range of frequency producing uniform droplet and the range of jet velocity producing uniform droplet decrease.The liquid with higher viscosity can break into uniform droplet in a more wider range of frequency and jet velocity producing uniform frequency.When the vibration frequency keeps a constant,as the increasing of the vibration amplitude,both the upper and lower limits of vibration frequency producing uniform droplet increase,while the range of the frequency producing uniform droplet almost remains unchanged...