The next generation of commercial gas turbine engines will require the further development of quieter, more fuel-efficient, and improved low-emissions technologies compared to existing engine designs. An essential role for achieving lower noise levels and higher fuel efficiency is played by the power transmission gear system connected to the fan. Consequently, future aircraft engine designs will require higher capability bearing compartment seals than found in current engine applications. Geared systems driving the fan will be subjected to inertia and gyroscopic forces resulting in extremely high angular and radial misalignments. Because of the high misalignment levels, compartment seals capable of accommodating angularities and eccentricities are required. Pratt & Whitney and Stein Seal Company selected the segmented circumferential carbon ring seal as the best candidate to operate at highly misaligned conditions. Initial seal tests established the misalignment limits of the current technology circumferential ring seal. From these results, a more compliant design, a three-ring seal configuration, was conceived, designed, fabricated, and tested. Further improvements to this compliant seal design are underway and plans are to conduct a durability test of the next phase configuration. A technical approach is presented, including design modifications to the "baseline" seal and the improved compliant design, carbon grade selection, test rig configuration, test plan and results of seal development testing and analysis of the data.
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