How do you make a turbofan more efficient? Connecticut based engine maker Pratt & Whitney (P&W) approached this dilemma by simply adding a gear. Their new PurePower PW1000G series engine utilizes an advanced gear system that allows the engine’s fan to operate at a different speed than the low-pressure compressor and turbine. The new gear system, along with an all new highly advanced core, delivers double digit improvements in fuel efficiency, environmental emissions and noise. Although this isn’t exactly new technology. Years ago Honeywell constructed geared engines for small private jets but never advanced the technology towards larger aircraft due to the difficulty of managing and expelling the heat quickly, which becomes more involved as thrust/size increases. P&W says the new PurePower engines will reduce carrier operating costs by 20%, dampen noise levels by half, and cut CO2 emissions by 3,600 metric tons a year.
To create thrust, modern turbofan engines expel fast moving hot gases from their cone, along with use of their fans to push slower air around the outside of the engine so it mingles with the faster hot gases at the rear. Typically, this could produce a bypass ratio of around 8:1, which means that for every 1 kg of air passing through the combustion chamber, 8 kg of air passes around the combustion chamber through the ducted fan alone. The higher the bypass ratio, the greater the engine’s thrust and efficiency. P&W’s PurePower line of engines has a 12:1 bypass ratio. The fan drive gear system (FDGS) is the catalyst of this new technological push, which leverages the basic laws of physics to improve propulsive efficiency. The robust, lightweight gearbox is capable of transmitting 30,000 lbs of thrust. The FDGS follows the fan shaft but separates the engine fan from the low pressure compressor and turbine. Rotating at a slower speed than the low pressure compressor and turbine, the fan allows for each engine module to operate at...
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