An Experimental Study On Breakup And Atomization Of Elliptical Power Law Fluid Jets

Liquid jets widely exist in many fields of nature and are extensively employed in engineering applications.The processes of breakup and atomization have important theoretical significance and engineering application background.Power law fluid has been widely used in our daily life.However,due to the complexity of the fluid itself,it is still inadequate to understand of the mechanism of fragmentation.With the prominent problems of energy and environment,some new alternative fuels with power-law fluid rheology have attracted people's attention.New ways for the injection system are needed to improve the atomization of such fuels.Therefore,studies on elliptical power-law fluid jet are not only helpful to enrich the theory of non-Newtonian jet breakup,but also have certain reference meaning for the optimization of the injection systems.Experimental systems that were suitable for elliptical low-velocity jet and high-velocity atomization were designed and constructed,which included: image information acquisition system,liquid transmission and collection system,injection system and control system.Test fluids included self-prepared power law fluid and water.The research includes: Under the conditions of low jet velocity,power-law fluid and water are compared to obtain the influence trends on jet development morphology,jet crushing mechanism,axial switching wavelength and different ovality.Different parameters,which included environmental parameters,physical properties of fluids and the ellipticity of orifice,were studied to acquire the trends of morphology parameters.For low velocity jets,the experimental results show that elliptic jets of power law fluid have obvious oscillation decay phenomenon on jet profiles.Different from “double peak” of water jet breaking curve,the curve of elliptical jet of power law fluid shows “single peak” form.In Rayleigh mode,the breakup scale of elliptical jet is less affected by ellipticity.In Taylor mode,the crushing length decreases with the increase of ellipticity.The slope of the water has nothing to do with the ellipticity,and the axial switching wavelength of the power law fluid has a linear relationship with the jet velocity.Besides,the slope increases with ellipticity.According to the modified one-dimensional dimensionless jet profile model,the larger Weber number causes larger axial switching wavelength and smaller amplitude.Higher ellipticity leads to larger axial switching wavelength,greater amplitude.Larger apparent Reynolds number results in little effect on axis switching wavelength and bigger amplitude;bigger power law index accounts to smaller axis conversion wavelength and smaller amplitude.For atomization of high-velocity jets,the experimental results show that: based on value of ellipticity,atomization process can be divided into three types,which include cylindrical jet atomization,low elliptical jet atomization and high elliptical jet atomization.Jet velocity,ovality,fluid properties and ambient pressure all affect jet atomization.Jet velocity and ambient pressure both promote jet atomization.For the high-viscosity power-law fluid,higher ovality cultivates atomization.For the low-viscosity power law fluid,within a certain range,the increasing ovality promotes crushing,but high ovality restrains breakup.The influences of different parameters on atomization of the low-viscosity power law fluid are similar to those of water.