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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.
A geared, variable pitch fan, replaced the first stage of the low pressure (LP) compressor. A modest fan pressure ratio, consistent with the high bypass ratio, meant a low fan tip speed could be employed. A low hot jet velocity was another major design feature.
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.
The UltraFan is a geared turbofan with a variable pitch fan system that promises at least 25% efficiency improvement. [84] The UltraFan aims for a 15:1 bypass ratio and 70:1 overall pressure ratio. [85] The Ultrafan keeps the Advance core, but also contains a geared turbofan architecture with variable-pitch fan blades.
Medium-bypass turbofan engines (17 P) T. ... Variable pitch fan This page was last edited on 23 March 2013, at 07:00 (UTC). Text is available under the Creative ...
One of the major differences between the F404 and the F414 is the fan section. The F414 fan is larger than that of the F404, but smaller than the F412 fan. [4] The larger fan increases the engine airflow by 16%, is 5 inches (13 cm) longer, and increased diameter from 28 inches (71 cm) to 31 inches (79 cm).
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 ...