General Electric YF120
| YF120 | |
|---|---|
| Type | Variable Cycle Turbofan |
| National origin | United States |
| Manufacturer | General Electric |
| First run | 1980s |
| Major applications |
Lockheed YF-22 Northrop YF-23 |
| Developed into | General Electric/Rolls-Royce F136 |
The General Electric YF120 was a variable cycle turbofan engine designed by GE Aircraft Engines in the late 1980s/early 1990s for the United States Air Force's Advanced Tactical Fighter (ATF) project (which resulted in the F-22 Raptor). GE lost the engine competition for this aircraft to Pratt & Whitney F119.
General Electric began developing the YF120 for the ATF competition in the early 1980s. Unlike competitor Pratt & Whitney, GE elected against developing a conventional low bypass turbofan and instead chose to design a variable cycle engine. This decision was made as a result of the challenging ATF requirement of supercruise. This meant the engine had to produce a large amount of dry thrust (without afterburner) and therefore have high off-design efficiency ("design" being standard cruise conditions).
The core technology used in the YF120 was developed during two industry-government programs, the Advanced Technology Engine Gas Generator (ATEGG) and Joint Technology Demonstration Engine (JTDE) programs.
On 3 November 1990, a YF-22 powered by two General Electric YF120s set a supercruise record of Mach 1.58.
The YF120's variable cycle system worked by varying the bypass ratio of the engine for different flight regimes, allowing the engine to act like either a low bypass turbofan or nearly a turbojet. As a low bypass turbofan (like competitor F119), the engine performed similarly to comparable engines. When needed, however, the engine could direct more airflow through the hot core of the engine (like a turbojet), increasing the specific thrust of the engine. This made the engine more efficient at high altitude, high thrust levels than a traditional low bypass turbofan.
An expected disadvantage of this variable cycle system would be increased complexity and weight. GE claims to have combated this by using simple pressure driven valves rather than complex mechanically actuated valves to divert airflow. GE stated that this system resulted in the variable cycle system adding only 10 lb to the engine. Additionally, a production F120 engine was expected to have 40% fewer parts than the F110 engine.
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