幾何因素對液體平軸封Lomakin效應和動態係數之影響

Influence of Geometric Factors on the Lomakin Effects and Dynamic Coefficients of Liquid Plain Seals

軸封在旋轉機械上的主要應用為控制洩漏量，流體經過軸封時，轉軸兩側流道出入口端壓降（pressure drop）分佈不同，會對轉子產生徑向作用力（radialforce）將轉子推回軸封中心位置，影響旋轉機械系統動態特性，此現象為Lomakin效應。影響Lomakin效應的幾何因素有：軸封的幾何外形，軸封間隙與半徑比，軸封表面粗糙度，轉子偏心量。過去文獻中Lomakin效應對於動態係數影響的分析上，均著重在主勁度係數的影響，此外影響Lomakin效應的各個因素也沒有完整的討論。本文利用CFD 軟體Fluent 來分析Lomakin 效應以求得更精準的動態係數，並針對幾何因素之影響作一詳細討論。

The major applications of seals in rotating machinery are to controlthe leakage of fluids. When the fluid passes through the seals, Lomakineffects are caused by the different distributions of pressure drop betweenthe opposite sides of the rotor, generating radial forces exerted on therotor and affecting the dynamic characteristics of the rotating machines.The geometric factors that may affect the Lomakin effects include ratioof seal length and shaft diameter, ratio of seal clearance to shaft radius,surface roughness, and eccentricity of the rotor. Previous research wasconducted mainly on the direct stiffness coefficients affected by theLomakin effects, without detailed investigation on the influence ofvarious geometric factors. In this paper, the influence of geometricfactors on the Loamkin effects and the dynamic coefficients are examinedby Fluent, a CFD software.