Soft Semi-Solid Deposit Formation of Lubricating Oil at Lower Temperatures below 200°C

Abstract

In the compressor housing of a turbocharger with oil mist atmosphere, soft semi-solid deposit could be observed even at the lower temperatures below 200°C. Sticky or hard deposit at higher temperatures above 300°C is well-known, which can be demonstrated by standard test such as the Panel Coker Test. However, the semi-solid deposit formation has not been reported and understood. In this research, the deposit in the compressor housing was analyzed and the formation mechanism was presumed basing on the composition of the deposit. To validate the presumption, the deposit formation was demonstrated using newly designed test method. Furthermore, the dependence of conditions on the formation and the countermeasure to prevent from deposit formation are also considered.