鐵磁性流體和表面粗糙度與磁場模式之複合效應對頸軸承液動潤滑性能影響分析

Lubrication performance of the journal bearings considering the effects of surface roughness and magnetic fluid

陳靖紘(Jing-hong Chen)

指導教授 ： 徐澤志

元智大學/工程學院/機械工程學系/博士(2013年)

https://doi.org/10.6838/YZU.2013.00059

摘要

本研究主要是在探討頸軸承內部的鐵磁性流體在表面粗糙度及外加磁場作用下的複合影響。以磁性流體動量和連續方程式及Christensen隨機粗糙度理論為基礎，並推導出頸軸承系統內部的磁性流體隨機修正雷諾方程式，並結合外加磁場模式，求解出頸軸承液動潤滑的壓力分佈，並用以計算軸承的性能，如荷重能力、姿態角與修正摩擦係數等。
研究結果顯示，磁性流體在表面粗糙度模式及磁場模式複合效應下對頸軸承系統操作性能具有不可忽略的影響。外加磁場確實可以提升軸承內部無因次壓力、改善負載能力和降低姿態角與修正摩擦係數，尤其是在高偏心率比和表面粗糙度及磁場複合作用下。於短頸軸承時，相較於表面光滑案例，縱向粗糙度可以增加無因次壓力Pmax值、無因次荷重能力和降低修正摩擦係數。橫向粗糙度則反之。長頸軸承時，橫向粗糙度可提升無因次壓力Pmax值、無因次荷重能力和降低修正摩擦係數優於表面光滑及縱向粗糙度模式。於有限長頸軸承近似模式下，隨長徑比增加(λ等於0.6, 0.95和1.8)，表面粗糙度模式對頸軸承系統會出現不同的影響。

關鍵字

鐵磁性流體 ； 隨機粗糙度模式 ； 磁場效應

並列摘要

This study investigated the combined influence of stochastic surface roughness patterns and a magnetic field on the distribution of hydrodynamic pressure in the journal bearings lubricated with ferrofluids. The influence of surface roughness on the lubrication system was determined according to Christensen’s stochastic roughness theory. A stochastic Reynolds equation for the journal bearing systems lubricated with non-Newtonian fluids was derived, and in conjunction with the magnetic field model, the distribution of pressure in the hydrodynamic lubrication in the journal bearing was solved and used to calculate the characteristics of the bearing, including loading capacity, attitude angle, and the modified friction coefficient.
According to the results obtained, the combined effects of surface roughness and magnetic field on the characteristics of journal bearing systems are apparently and can be negligible. Comparing to ferrofluid lubricant smooth bearing case, the magnetic field effects can raise the dimensionless pressure of the lubricant fluid, improved the dimensionless load capacity and reduce the attitude angle and the modified friction coefficient, especially at higher eccentricity ratio, surface roughness and magnetic field. The surface roughness effect is dominant in the different journal bearing system. In the short bearing case, compared to the smooth surfaces, the longitudinal roughness can increase Pmax, dimensionless loading capacity and reduces the modified friction coefficient. Transverse roughness has the opposite effect on the operational performance of bearings. In the long journal bearing, the transverse roughness enhances Pmax value, dimensionless loading capacity and reduces the modified friction coefficient more than smooth and longitudinal roughness pattern. In the finite journal bearing, the journal bearings Characteristics are also influenced by surface roughness pattern depend on the length to diameter ratio λ, and the critical value of λ equal to 0.6, 0.95 and 1.8 in this study.

並列關鍵字

ferrofluid ； stochastic surface roughness ； magnetic field

參考文獻

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