新しい熱伝達モデルを組み込んだ熱流体潤滑モデル

摘要

ティルティングパッドジャーナル軸受（Fig.1) は，予圧係数が比較的高くダブルティルト構造（円 周方向にも軸方向にも傾斜可能な構造）の軸受パ ッドを採用すれば実用回転速度の範囲でオイルホイッブを回避できる"ため，高速回転機械の支持 軸受に多用されている.回転機械の大型化が進む と，油膜内で発生するせん断発熱が増大し.これ に接するパッド潤滑面の温度は上昇する.パッド 潤滑面には，異物埋収性に優れたホワイトメタル のような低融点の軟質金属がライニングされてい るため，熱流体潤滑(Thermo-Hydrodynamic Lubrication,以下THL)理論を用いて運転中の パッド潤滑面温度が上限値以下になることを設計 段階で確認する必要がある.%Thermo-hydrodynamic lubrication (THL) models have been applied at the design stage of large-sized high-speed rotary machineries to confirm that the maximum surface temperature of sliding bearing, such as tilting pad journal bearing, under operation is below the upper limit. A single common value of heat transfer coefficient is given between the environment and the five surfaces other than the lubricating one of each pad regardless of operating conditions and/or bearing specifications in the traditional THL model, while a new THL model is proposed with non-traditional heat transfer model incorporated. In this model, the value of locally distributed heat transfer coefficient is determined depending on the operation conditions and/or the bearing specifications. Using the model, it is unnecessary to determine the heat transfer coefficient by an unreasonable estimation, and it is found that the predicted maximum pad surface temperature and also the distribution of pad surface temperature are in good agreement with the measurements.