Numerical study on the morphology of a liquid-liquid pintle injector element primary breakup spray

Abstract

Primary breakup in a liquid-liquid pintle injector element at different radial jet velocities is investigated to elucidate the impingement morphology, the formation of primary breakup spray half cone angle, the pressure distribution, the liquid diameter distribution, and the liquid velocity distribution. With a sufficient mesh resolution, the liquid morphology can be captured in a physically sound way. A mushroom tip is triggered by a larger radial jet velocity and breakup happens at the tip edge first. Different kinds of ligament breakup patterns due to aerodynamic force and surface tension are captured on the axial sheet. A high pressure core is spotted at the impinging point region. A larger radial jet velocity can feed more disturbances into the impinging point and the axial sheet, generate stronger vortices to promote the breakup process at a longer distance, and form a larger spray half cone angle. Because of the re-collision phenomenon the axial sheet diameter does not decrease monotonically. The inner rim on the axial sheet shows a larger diameter magnitude and a lower velocity magnitude due to surface tension. This paper is expected to provide a reference for the optimum design of a liquid-liquid pintle injector.

概要

目的

针对液/液针栓式喷注器单元, 研究其在不同径 向射流喷注速度下的一次破碎形态, 并阐明在一 次破碎下喷雾半锥角的形成、压力场分布、喷雾 粒径分布与速度场分布.

创新点

通过流体体积函数转换离散相(VOF-to-DPM) 模型, 结合网格自适应(AMR)技术还原了针栓 式喷注器单元液/液撞击的一次破碎形态.

方法

1. 通过VOF-to-DPM 模型完成一次破碎过程中对 液相的捕捉; 2. 采用计算流体动力学后处理 (CFD-post)模块进行后处理, 得到一次破碎下 喷雾半锥角的形成以及压力场、喷雾粒径与速度 场的分布云图; 3. 在仿真计算过程中使用AMR 技术减少计算量, 节约时间成本与计算资源.

结论

1. 速度大的径向射流在穿透轴向液膜后会形成一 个蘑菇状的头部; 扰动在蘑菇状顶端下方形成 涡, 有助于蘑菇状顶端边缘破碎的发生. 2. 气动 力和表面张力对轴向液膜破碎过程中产生的直 液丝和环状液丝的破碎起到重要作用; 由于液滴 的聚合现象, 轴向液膜的直径在破碎过程中并不 是单调递减的. 3. 喷雾半锥角的大小和径向射流 速度的大小成正比; 次破碎首先发生在轴向液 膜前沿、径向射流头部以及撞击点附近. 4. 在表 面张力的作用下, 轴向液膜内边缘的速度较小, 直径较大; 当径向射流的速度增大时, 轴向液膜 内边缘的速度值减小得更加明显.