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A variable pitch fan is similar in concept to that of a variable-pitch propeller and involves progressively reducing the pitch (or blade angle) of the fan on a turbofan as the engine is throttled. Although variable pitch fans are used in some industrial applications, the focus of this article is on their use in turbofan engines .
The Turbomeca Astafan is a single-spool, variable-pitch turbofan engine developed from the Turbomeca Astazou. [1]: 553 [2]: 932 Despite successful flight-testing, an efficient, quiet and clean design (compared to turbojets and conventional turbofans) [1]: 554–555 [3]: 1648 [4]: 1872 and some commercial interest, [5]: 1683 the Astafan never entered series production.
Its 118.2 in (300 cm) fan with 18 reversing pitch composite blades had a 15:1 bypass ratio. It aimed to cut fuel consumption by 6–7%, emissions by 15%, and generate less noise due to lower fan tip speed of 950 ft/s (290 m/s), down from 1,400 ft/s (430 m/s) in conventional 5:1 bypass turbofans.
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. [3] As a low bypass turbofan (like competitor F119 ), the engine performed similarly to comparable engines, with the aft bypass channel behind the ...
In the 1970s, Rolls-Royce/SNECMA tested a M45SD-02 turbofan fitted with variable-pitch fan blades to improve handling at ultralow fan pressure ratios and to provide thrust reverse down to zero aircraft speed.
A CJ805-21 turbofan on display at Flugausstellung Hermeskeil. Note the visible fan stage at the rear of the engine casing, unlike the more common shaft driven fan located to the front. Type Turbojet (CJ805) Turbofan (CJ805-23) National origin: United States: Manufacturer General Electric Aircraft Engines: Major applications: CJ805: Convair 880
Category: Turbofan engines. 19 languages. ... Variable pitch fan This page was last edited on 23 March 2013, at 07:00 (UTC). Text is available under the Creative ...
The General Electric F404 and F412 are a family of afterburning turbofan engines in the 10,500–19,000 lbf (47–85 kN) class (static thrust). The series is produced by GE Aerospace. Partners include Volvo Aero, which builds the RM12 variant. The F404 was developed into the larger F414 turbofan, as well as the experimental GE36 civil propfan.