多级轴流叶片除雾器阻力与分离性能研究

Research on the Pressure Resistance and Separation Performance of Axial Flow Blade Demister with Multi-Stage

轴流叶片除雾器是海洋船舶机舱进气系统的核心部件,用于去除海面空气中的高浓度盐雾气溶胶,防止对下游设备造成腐蚀。鉴于常规除雾器对雾滴和空气的总体分离机制存在固有局限,提出合理增加轴流叶片级数的改进设想。采用计算流体力学(CFD)理论和方法,对单级、两级和三级叶片除雾器内的气液两相流场进行数值模拟,重点考察进气流速范围1~7m/s、雾滴粒径10~100μm时,叶片级数对阻力和分离效率特性的影响。研究发现:1)叶片下游未被分离的雾滴主要集中于近壁面的薄层区域内,通过串联叶片可进一步挤压高浓度区范围,促进二次分离;2)增加叶片级数具有压力缓释作用,使得下游的流动能耗减小,额外阻力增幅微弱;3)相比传统的单级叶片,使用两级叶片足以将除雾效率有效而经济地提升至接近100%。

Axial flow blade demister is the core component of the air intake system in the marine engine room,which is used to remove high concentration salt mist aerosol from air on the sea surface and prevent the downstream equipment from being corroded.In view of the inherent limitations of the general separation mechanism of mist droplets and air by conventional demisters,an improvement idea of reasonably increasing the stage of axial flowblade was put forward.By using the Computational Fluid Dynamics(CFD)theory and method,the gas-liquid two-phase flow fields in the single-stage,twostage and three-stage blade demisters were numerically simulated,and the effects of blade stages on the characteristics such as pressure resistance and separation efficiency were mainly investigated when the inlet flow rate was in the range of 1-7 m/s and the droplet size was 10~100μm.Findings:1)The unseparated droplets at the downstream of the blades are mainly concentrated in the thin layer near the wall,and the high concentration area can be further squeezed by connecting the blades,thus promoting the secondary separation.2)Increasing the stage of blade has a pressure relief effect,which reduces the downstream flow energy consumption and makes the additional pressure resistance increase weakly.3)Compared with the traditional single-stage blade,using two-stage blade is enough to effectively and economically improve the demist efficiencyto nearly100%.