How GE’s Adaptive Engine Differs From Earlier Variable-Cycle Designs | GE社のアダプティブエンジンと、従来の可変サイクルエンジン設計の違い

GE engine concept
Blue marks the cooler third stream flow on this simplified GE concept.
Credit: GE Aviation

新世代のアダプティブサイクルエンジンの作動サイクルはまだ明らかになっていないが、GE XA100/P&W XA101とそれ以前の可変サイクルエンジン(1980年代のGE社製XF120など)の大きな違いは、コアの空気流と通常のバイパスダクトとは別に、第3の空気流を持つことだ。可変エリアノズルとアダプティブインレット機構を協調制御することで、通常のバイパスダクトに加えて第3の空気流の調整が可能になる。この組み合わせにより、燃費と推力に影響を与える重要な2つの要素、つまりファン圧力比と全体のバイパス比を動的に変化させることができる。



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Details of the operating cycles of the new-generation adaptive engines remain sparse, but the key difference between the GE XA100/P&W XA101 and earlier variable-cycle concepts such as GE’s XF120 from the 1980s is the addition of the third air stream, which is external to both the core flow and standard bypass duct. Adaptive inlet devices, working in combination with a variable-area nozzle, modulate the flow in the third stream as well as the conventional bypass duct. The combined devices dynamically alter the fan pressure ratio and overall bypass ratio—the two key factors influencing specific fuel consumption and thrust.

This contrasts with the XF120, also known as the GE37, which employed a double-bypass approach to vary the cycle using a series of fan bypass doors, core bypass ducts and a variable-area bypass injector (VABI) aft of the low-pressure turbine. When the engine was operating in turbofan mode, both the fan and core bypass were open and the VABI closed. The injector, which helped to match the fan-to-core pressure, provided cooling air to the exhaust liner.

When the engine was in turbojet mode, the fan bypass door was closed, and a smaller amount of air was discharged into the bypass through the core bypass duct. The fan supercharged the engine core, and the VABI, which was located upstream of the afterburner, was opened to reinject the remaining bypass stream into the throat of the exhaust.