Development of an apparatus for the degradation of aviation gas turbine lubricants

The capabilities of the Lubricant System Interaction Simulator (LSIS) are demonstrated by presenting the results from a 1,000-h thermal oxidative degradation test of an MIL-PRF-23699F lubricant. These results are compared with data from two in-service gas turbine engines using the same oil but under different conditions so that a range of operating regimes can be represented. The results showed that the viscosity changed, in accordance with the two engines, from 26.5 to 28.3 mm²/s. The change in total acid number was higher than expected, identify- ing areas for improvement. The antioxidant level reached 30%, which is between the 25% and 45% levels observed from the two engines. The antiwear and metal deactivator additives reached steady-state concentration levels of 95% and 20%, respectively. The results obtained from this test verified the significant potential of this facility as a reliable means of testing lubricants in an environment that is closely related to gas turbine lubrication system operating conditions.