Experimental Study On Breakup Characteristics Of Sheet Formed By Impinging Jets

The research on breakup mechanism of the liquid jet is not only a traditional fluid mechanics problem,but also of great theoretical research value and engineering application background.In which the liquid sheet formed by two impinging jets is a classic method of jet atomization for its simple structure,low cost,excellent atomization and has been widely applied to many fields including aeronautics and astronautics.For this paper,the breakup progress and characteristic of the liquid sheet were studied under the condition of speed less than 20 m/s.A set of experimental facility composed of sub-systems like liquid feeding system,jet impinging system,data acquiring system was built to characterize the breakup of liquid sheets formed by impinging jets.High-speed photography was used to investigated the atomization behavior of water,glycerol solution and non-Newtonian power-law gelled fluids which show a shear-thinning behavior.The breakup characteristics including stripping breakup length,length of liquid film,width of liquid film and aspect ratio were defined and extracted from the optical shadow pictures.The impact on the breakup of liquid film of different factors,such as jet impact angle,shape of nozzle orifice,viscosity,momentum ratio of the two jets etc ware analyzed.Breakup regime of symmetric and antisymmetric impinging involved Newtonian and non-Newtonian fluid was researched.Various breakup characteristics of different fluids were compared.Present results indicate that both impact angle and jet fluid contribute to the breakup regime.The breakup regimes of water include closed rim pattern,open rim pattern and completely breakup pattern;for glycerol solution,different density contribute to different breakup regime.As to Carbopol gel,liquid ligament and drop pattern is observed.Experimental results show that the shape of nozzle orifice has a good effect on the process of breakup.For round nozzle orifice,the smaller the diameter is,the better atomization is.Whtat's more,rectangle nozzle orifice is better at promoting the breakup of impinging jet under the same condition than other shape of nozzle orifice.