Abstract
This paper describes the multistate analysis and design optimization of the lubrication system for a high bypass ratio geared turbofan (GTF) engine in the 20,000 to 30,000-lbf thrust class. Whereas traditional turbofan engines have a fixed shaft connecting the fan with the low-pressure turbine and compressor, the GTF engine has a fan drive gear system that couples the fan to the low pressure spool, allowing the fan and associated compressor and turbine to be operated at more efficient wheel speeds. This has advantages of improving fuel efficiency and reducing noise levels, but results in a more complex and operationally critical lubrication system. In order to ensure safe and satisfactory operation of the GTF across several operating states, a methodology is hereby used in the optimization of the lubrication design that treats it as a multistate system, where the states are defined by distinct levels of performance brought about by changes or failures in system components. Results indicate that when compared to the traditional, nominal case design as a baseline, performing the multistate design analysis improves the overall system expected availability by as much as 7% over a 500 hour period of operation. Furthermore, this result is obtained by making changes to the system’s static architectural design variables rather than component failure rates, the only area typically under consideration during traditional reliability analysis.
Published Version
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