Accumulated Thermal Damage Analysis of Synthetic Turbine Engine Oils

A method is proposed to equate actual operating oil temperature/time profiles to a single oil test temperature/time. This calculated equivalent oil temperature can be used to determine the useful life of oil versus temperature for thermal degradation.

A single oil temperature can be selected for an accelerated test which equates to long duration, multi-temperature conditions.

This paper uses Allied-Signal Aerospace Company test data for Mobil Jet II oil life versus temperature and employs an accumulated damage model similar to Miner's rule to determine oil life. This paper (1) defines useful life (2) calculates the life exponent for the accumulated damage equivalent life equation, and (3) presents a sample where it is used.

The method is proposed for consideration and comments since oil thermal degradation is a complex process with nonlinearities in various stages due to chemical inhibitors.