Pratt & Whitney · Case study
Pratt & Whitney GTF (PW1000G)
The defining efficiency idea of the 2010s narrowbody generation: a reduction gearbox that lets the fan turn slowly and the low-pressure spool turn fast, each near its own aerodynamic optimum.
Architecture
A planetary reduction gearbox of roughly 3:1 sits between the fan and the low-pressure spool. A large fan is most efficient turning slowly; a low-pressure compressor and turbine are most efficient turning fast. In a conventional engine they are locked to the same shaft and neither gets its wish. The gear decouples them.
Because the LP spool can now spin fast, it needs far fewer compressor and turbine stages, cutting part count and weight, while the slow fan can be large for a high bypass ratio and quiet operation.
The cycle
The pay-off is a double-digit fuel-burn improvement at entry, plus a marked noise reduction from the slow fan tip speed. The engineering price is a heavily loaded gearbox that must transmit tens of thousands of horsepower and shed significant heat reliably — the focus of much of the programme's early service experience.
Engineering significance
The geared turbofan reopened a design space the industry had largely set aside, and proved a gearbox could be made durable at large-engine power levels. It now competes directly with the LEAP across the single-aisle and regional-jet market.
Applications
Airbus A320neo · Airbus A220 · Embraer E-Jets E2
Explore a representative turbofan cycle for this engine class in the interactive console.
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