METHOD FOR SETTING A GEAR RATIO OF A FAN DRIVE GEAR SYSTEM OF A GAS TURBINE ENGINE

摘要

In one exemplary embodiment, a gas turbine engine includes an engine centerline longitudinal axis. A fan section includes a fan with a plurality of fan blades. The fan has a low corrected fan tip speed less than 1400 ft/sec. A bypass ratio is greater than 13 and less than 20. A fan pressure ratio less than 1.38 at cruise conditions of 0.8 Mach and about 35,000 feet. A speed reduction device comprises a gear system with a gear ratio of at least 2.6 and less than or equal to 4.1. A low pressure turbine is in communication with a first shaft. A high pressure turbine is in communication a second shaft. The first shaft is in communication with the fan through the speed reduction device. The low pressure turbine includes at least three stages and no more than four stages. The high pressure turbine includes two stages.