Experimental Investigation On Breakup Characteristics Of Power-law Fluid Jets

As a non-Newtonian fluid,Power-law fluid has a wide range of applications in aerospace,chemical,agricultural and other fields.As a gas-assisted atomizing nozzle,the annular nozzle can effectively promotes the breakup process of low-pressure liquid jets.Researchers are currently studying the breakup characteristics of Newtonian fluid annular jets,and the researches about breakup characteristics of Power-law fluid annular jets is insufficient.In addition,the current researches about Power-law fluid mainly focuses on the investigation of low-pressure liquid jets,and the researches on high-pressure liquid jets is also insufficient.In this paper,a low-pressure annular jet experimental system and a high-pressure cylindrical jet experimental system are built.The high-speed camera measurement system and PIV measurement system are used to study the breakup regimes and breakup and atomization characteristic parameters of the jets and sprays.The experimental results of the low-pressure annular jets of Power-law fluid show that both Newtonian fluid jets and Power-law fluid jets have Christmas tree breakup regime,bubble breakup regime and wave-assisted breakup regime.And there is no essential difference between the two fluids in the breakup mechanism.The breakup condition is significantly deteriorated as the viscosity of the Carbopol gel increases.The surface wavelength of the jets increases as the liquid velocity increases and decreases as the gas velocity increases.Based on the empirical formula given by Lozano et al and the theoretical analysis of the annular jets,the formula relating the dimensionless wavelength to the gas velocity,liquid velocity and fluid rheological properties is proposed,The dimensionless surface wavelength in the equation increases linearly with the increase of the parameter T.The experimental results of the high-pressure cylindrical jets of Power-law fluid show that the high-pressure jet spray of Newtonian fluid(water,diesel)and Power-law fluid(Carbomer solution)has similar morphological characteristics.The increase of injection pressure and background pressure and the decrease of orifice diameter are beneficial to the high-pressure jet breakup and atomization process of Power-law fluid.The increase of the viscosity of Newtonian fluid and Power-law fluid is adverse to the breakup and atomization process of the liquid jets.The velocity of at the axis of the orifice is continuously attenuated along the direction of the jets,and the velocity of the droplet at the cross section of the sprays exhibits a Gaussian distribution.The larger the jet pressure and the diameter of the orifice,the higher the velocity of the droplet.Under the same injection pressure and background pressure conditions,the velocity of water,diesel,Carbopol 0.15 wt.%,Carbopol 0.25 wt.% gradually increased,and the relationship between the velocity of the four fluids was consistent with the viscosity of the fluids.For the Power-law liquid jets under a certain injection pressure,the consistency coefficient K is still the dominant factor controlling the viscosity of the Power-law fluid,and the Power-law index n has a relatively small effect on the viscosity of the Power-law fluid.