July 6, 2008 Pratt & Whitney’s Geared Turbofan demonstrator engine has been cleared for flight-testing. By incorporating a gearbox system into the engine, aircraft can achieve a 12% reduction in fuel burn and CO2 emissions, a 50% reduction in NOx emissions, and a 50% reduction in engine noise. The GTF engine has been chosen by Mitsubishi to power the company’s Regional Jet (scheduled to enter service in 2013), and the upcoming Bombardier CSeries.
In order to achieve optimal thrust, and maximum engine efficiency, the exhaust speed of jet engines needs to be synchronized with the flying speed of the aircraft. Traditionally, engines use turbines to siphon the excess power from the exhaust and power a propeller. The Geared Turbofan, however, uses a gearbox, not a low pressure turbine, to power a fan. This allows the fan, low pressure compressor, and turbine to operate at different speeds. By incorporating an extra layer of complexity into engine design, the gearbox allows far more efficient regulation of fan speed, resulting in decreased fuel use and noise.
The Geared Turbofan has a fan tip diameter of 56-78-inches, a bypass ratio of 8-12, and provides a takeoff thrust of 15,000-30,000 pounds. Pratt & Whitney estimate that the increased efficiency will translate to savings of $1.5 million per aircraft, per year.
“The double-digit reductions in fuel burn, engine noise, environmental emissions and operating costs we’ve targeted make the Geared Turbofan engine the best solution for the next generation of commercial aircraft.”