龙卷旋涡的真空与能量分离特性研究

Vacuum and energy separation characteristics of tornado-like vortices

为深入认识龙卷旋涡的气动特性,探索旋涡的形成条件,该文基于Ranque-Hilsch效应设计了若干旋射管,并通过流场可视化和参数测量,对龙卷旋涡的真空度和能量分离特性进行了研究。结果表明:龙卷旋涡依靠强旋同时产生真空吸引和离心扩张2种相反的效应,维持了很小的射流张角和良好的气动封闭性;旋涡具有对外的屏蔽效应和与环境气体之间的滑移效应,维持了射流中心的高真空区、真空度"火山口"状非均匀径向分布和指数型式轴向衰减特征;旋涡具有很强的能量分离效应,与当地真空度和气流流动方向密切相关;进气压力和高真空度是形成龙卷旋涡的充要条件,压力能转化为旋转动能的比例随压力增高而加大;优化旋射管结构可提高能量转化效率。研究结果为揭示龙卷旋涡的生成机理以及研究旋涡与燃烧之间的相互作用提供了重要依据。

A series of Ranque-Hilsch-effect-based vortex generators were designed for cold-state flow tests of tornado like vortices. Flow visualizations and measurements show that the opposing effects of vacuum abstraction and centrifugal expansion are both derived from the intensive swirling which leads to small jet angles and less aerodynamic leaks than in a normal swirling jet. The vortex provides a slip and shielding effect to the environment, a high vacuum region in the center of the vortex and an inhomogeneous volcano-like velocity distribution with exponential attenuation of the vacuum in the axial direction. Energy separation accuses which is closely related to the local vacuum and flow direction. A high inlet pressure and vacuum are crucial to the vortex generation and the proportion of the energy conversion from pressure to swirling kinetic energy increases with increased pressure, which can be used to optimize the generator structure. The tornado-like vortex generation mechanism can be used to study the interaction between the vortex and combustion in the vortex.