Variable Pitch Fan With 80-130 Degree Range
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Solution Overview
Problem
Existing variable pitch fans for propulsion devices, such as gas turbine engines, are limited by a restricted pitch range due to design parameters like solidity and component configurations, which restricts their performance and efficiency, especially in varying flight phases and thrust reversal.
Innovation Solution
A variable pitch fan design with a larger pitch range of 80° to 130°, increased solidity in the root region, and a reduced fan hub radius ratio and pressure ratio, achieved through a disk-based configuration with rotatable fan blades and a pitch change actuation assembly that allows asynchronous blade pitching, enabling efficient thrust reversal without heavy mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the pitch range is increased to improve performance across different flight phases, then the fan's adaptability and efficiency are improved, but the device complexity and structural constraints worsen
Solution Approach 1:
The fan blades are designed with variable pitch capability, allowing them to rotate about pitch axes to change their angle of attack dynamically. This enables the fan to adapt to different flight phases (takeoff, cruise, landing) and power levels by adjusting the blade pitch angle, thereby improving performance across the entire operating envelope without requiring multiple fixed-pitch fans
Solution Approach 2:
The pitch range is explicitly increased to 80-130 degrees, representing a significant parameter change from conventional designs. This expanded pitch range allows the fan to operate efficiently across diverse conditions while maintaining optimal aerodynamic characteristics through precise pitch control
2Productivity
If the solidity in the root region is increased to improve aerodynamic efficiency, then the fan's performance is improved, but the device complexity and manufacturing difficulty worsen
Solution Approach 1:
The solidity is specifically increased in the root region of the fan blades where it is most needed for aerodynamic efficiency, rather than uniformly across the entire blade. This localized approach optimizes performance in the critical root area while managing manufacturing complexity by concentrating the enhanced structure where it provides maximum benefit
3Productivity
If the fan hub radius ratio is decreased to improve performance, then the aerodynamic efficiency is improved, but the device complexity and structural challenges worsen
Solution Approach 1:
The pitch axes are positioned at a radial distance from the fan hub center, creating a three-dimensional pitch control mechanism. This spatial arrangement allows the blades to rotate about off-center axes, enabling the reduced hub radius ratio design while maintaining structural integrity and control capability through the distributed pitch axis configuration
Data Source
AI summary
A variable pitch fan for a propulsion device is provided. The variable pitch fan includes a plurality of fan blades coupled to a disk and a rotatable front hub covering the disk. Each fan blade is rotatable about a pitch axis to vary a pitch of the fan blade. The pitch is variable within a pitch range that is at least about 80° to about 130°. Each fan blade extends radially outward from the disk along a span from a root to a tip. A portion of the span adjacent the root defines a root span region, a portion of the span adjacent the tip defines a tip span region. A solidity of the variable pitch fan is at least 1.0 in the root span region.