幂律流体环膜射流破碎特征的试验

Experimental Study of the Breakup Characteristics of Power Law Fluid Annular Jets

通过自行搭建的环膜射流试验系统,采用高速摄影技术对牛顿流体(水)与剪切变稀型幂律流体(卡波姆凝胶)环膜射流的破碎模式及破碎特征进行了试验.结果表明:牛顿流体与幂律流体都存在相同的3种射流破碎模式,且两种流体在射流破碎机理上没有本质性的差异.在3种射流破碎模式中,圣诞树状破碎模式下的射流破碎效果最佳,泡状破碎模式次之,波辅助破碎模式下的射流破碎效果最差.且射流破碎效果随卡波姆凝胶黏度的增加而显著恶化;射流的表面波波长随液体速度的增加而增加,随气体速度的增加而减小.与水相比,卡波姆凝胶射流的表面波波长受液体速度的影响更加明显.在高气/液速度比条件下,气/液剪切作用力是影响射流破碎的主导因素.基于环膜射流的理论分析结果和经验公式,提出了量纲为1波长与射流气/液速度、流体流变特性相关联的公式,式中量纲为1波长随参数T的增加逐渐增加.

Through the self-built annular jet system,the high-speed photography technology was used to study the breakup regimes and characteristics of Newtonian fluid-water and shear thinning power law fluid-Carbopol gel annular jet.The experimental results show that both Newtonian fluid and power law fluid have three kinds of jet breakup regimes,and there is no essential difference between the two fluids in the breakup mechanism.Among them,the breakup condition of jet under the christmas tree-like breakup regime is the best,followed by the bubble breakup regime,and the breakup condition of jet under the wave-assisted breakup regime is the worst.Furthermore,the jet breakup condition is significantly deteriorated as the viscosity of the Carbopol gel increases.The surface wave length of the jet increases as the liquid velocity increases and decreases as the gas velocity increases.Compared with that of water,the surface wave length of Carbopol gel is more affected by the velocity of the liquid.Under the condition of high gas-liquid velocity ratio,the gas-liquid shearing force is the dominant factor affecting the jet breakup process.Based on the empirical formula and the theoretical analysis of the annular jet,the formula relating the dimension of 1 wavelength to the gas-liquid velocity and fluid rheological properties was proposed,in which the dimension of 1 wavelength in the equation increases with the increase of the parameter T.