倒角阀座式水压锥阀空化射流动态行为数值模拟

Numerical Investigation of Dynamic Behavior of Cavitating Jet Through Water Poppet Valve with Chamfered Valve Seat Structure

使用可压缩的VOF空化两相流算法对倒角型阀座水压锥阀的空化射流进行了三维瞬态流场仿真。模拟结果揭示,空化结构首先在狭窄的倒角阀座流道内以附着空化的形式出现;在压差为4.4 MPa的工况条件下,空化分布集中在3个区域,阀座流道内及阀芯后沿的附着型空化,阀座流道至阀芯后沿的漩涡空化。射流势核在阀座流道入口及阀芯后沿均有分离流现象,从而诱发附着型空化;而大尺寸漩涡结构主要分布于射流势核的自由剪切层侧,漩涡空化亦相应地集中在自由剪切层侧,壁面侧偶发性形成薄层型漩涡空化。由于整体的空化行为涉及多个不同类型空化的耦合,其动态演变的周期特性受到干扰。阀座流道后部的脱落空化伴有明显的三维漩涡结构,阀芯后沿的漩涡空化与附着空化通过耦合作用形成大尺寸汽泡结构,揭示了后沿下游稀疏分布的大尺寸空化结构的产生过程。通过开展三维瞬态模拟,结合流场结构探索了空化射流的动态特性,从流体力学的层面解释了实验观测到的空化形态及分布规律。

A compressible VOF method is used to simulate the 3-D transient cavitating jet inside a water chamfered poppet valve.Cavitation first occurred as attached cavitation within the chamfered groove.At 4.4 MPa pressure drop,cavitation is mainly distributed in three regions,including the attached cavitation within the chamfered groove,attached cavitation at poppet trailing edge,and vortex cavitation at downstream of poppet trailing edge.The jet potential core involves flow separation at chamfered groove inlet and poppet trailing edge,contributing to the attached cavitation at the corresponding region.And the large-size vortex structure is mainly located within the free shearing layer of the jet potential core,interpreting the concentration of vortex cavitation at the free shearing side.Occasionally,vortex cavitation featured with a thin-layered morphology appears on the poppet wall.Because of the correlation between different cavitation,the dynamic periodicity suffers from remarkable perturbation.The detached cavitation at the rear chamfered groove is accompanied by development of 3-dimensional vortex,while large-size bubble is created through coupling between vortex cavitation and attached cavitation at poppet trailing edge.Through such a 3-D transient simulation,the current study explores the dynamics of the cavitating flow,revealing the mechanisms for the cavitation morphology and distribution.