高压环境下剪切稀化非牛顿撞击射流直接数值模拟

Direct numerical simulation of impinging jet with non-Newtonian shear thinning properties at high ambient pressure

高压环境下的撞击射流是液体火箭推进系统中广泛采用的一种燃料雾化方法,其雾化效果将直接决定最终燃烧效率。采用直接数值模拟(DNS)工具,对10MPa高压环境下剪切稀化非牛顿直角撞击射流的三维非定常雾化特征、机理及非牛顿特性进行了研究。结果表明:高压环境下该撞击射流的雾化流场呈圆形辐射状分布并形成Mushroom头部和Ω状的局部凸起,气体中的涡量分布表现为有序贴附区和无序爆炸区两类,液膜向液丝的破碎主要受平均气体力和平均黏性力作用影响,而液丝向液滴的破碎则主要受局部流场参数影响,撞击雾化过程中液体无量纲表面积不断增长并可分为5个阶段。此外,撞击射流头部在局部强剪切力作用下其无量纲黏性系数最低降至仅0.7。

Impinging liquid jets have been widely used in liquid rocket propulsion systems as a fuel atomization method.The breakup efficiency of impinging liquid jets directly determines the mixing and combustion efficiency of the fuel.The present work applies a Direct Numerical Simulation(DNS)tool to study the three-dimensional unsteady impinging jet breakup with non-Newtonian shear thinning properties at high ambient pressure 10 MPa,including the three-dimensional structure,breakup mechanism,and non-Newtonian feature of the liquid.The results indicate that the impinging jet breakup exhibits a radial circular flow structure and forms a Mushroom head and anΩshape local protruding.The distribution of gas vorticity is split into two categories that include the regulated attached region and irregular blasting region.The breakup from liquid sheet to ligament is determined by the average air force and viscous force,whereas the breakup from ligament to droplet is determined by local flow parameters.The dimensionless liquid surface area increases with time and can be divided into five phases.Additionally,the non-dimensional viscosity of the liquid at the impinging jet head decreases to only 0.7 due to high local shear stresses.