Geared Fan Section With Low-Solidity Blades for Noise-Efficiency Balance
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Solution Overview
Problem
Existing aeronautical propulsion systems face challenges in optimizing the fan section for improved propulsive efficiency while minimizing mass and specific consumption, particularly with high bypass ratios, which often result in excessive noise and inefficient energy use.
Innovation Solution
The fan section is designed with a fan rotor having 17 to 20 blades, a solidity less than 1.0, a pressure ratio of 1.05 to 1.5, and a peripheral speed of 260 to 400 m/s, combined with a reduction mechanism to decouple the fan rotor from the low-pressure shaft, optimizing rotational speeds and reducing pressure ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the fan section is designed with high bypass ratio to improve propulsive efficiency, then propulsive efficiency is improved, but noise emitted by the fan section increases
Solution Approach 1:
The patent applies parameter changes by optimizing the number of fan blades (17-25 blades) and controlling the solidity ratio (strictly less than 1.0) to modify the aerodynamic characteristics of the fan section. These parameter adjustments allow the system to maintain high propulsive efficiency while reducing noise generation through optimized blade geometry and spacing.
2Productivity
If the fan section is decoupled from the low-pressure turbine using a reduction mechanism to independently optimize rotational speed, then propulsive efficiency is improved, but device complexity increases
Solution Approach 1:
The patent introduces a reduction mechanism as an intermediary component between the low-pressure shaft and the fan rotor. This intermediary device enables independent optimization of the fan's rotational speed while maintaining the benefits of a decoupled architecture, achieving improved propulsive efficiency despite the added mechanical complexity.
3Productivity
If the fan section dimensioning is optimized with large diameter to achieve high bypass ratios, then propulsive efficiency is improved, but mass of the fan section increases
Solution Approach 1:
The patent employs parameter changes by establishing specific design constraints including a solidity ratio strictly less than 1.0 and an optimized blade count (17-25 blades). These parameter modifications enable the fan section to achieve high bypass ratios and improved propulsive efficiency while controlling the mass through optimized dimensional parameters and geometric configuration.
4Object-generated harmful factors
If the number of fan blades is increased to reduce noise, then noise is reduced, but mass of the fan section increases
Solution Approach 1:
The patent applies parameter changes by defining an optimal range for the number of blades (17-25) and controlling the solidity ratio (strictly less than 1.0). This parameter optimization allows the system to achieve noise reduction through increased blade count while simultaneously controlling the mass increase through appropriate geometric and dimensional adjustments.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enhances propulsive efficiency, reduces specific consumption, and manages supersonic shocks, resulting in a more efficient and compact propulsion system with stable thrust density and reduced noise.
Implementation Method 1
a fan rotor (9) comprising at least seventeen blades (14) and at most twenty blades (14) and having a solidity strictly less than 1.0
Implementation Method 2
The rotor of the fan section is then driven by the low-pressure shaft via the reduction mechanism at a rotational speed lower than that of the low-pressure shaft
Data Source
AI summary
A fan section of an aeronautical propulsion system includes a fan rotor including seventeen blades to twenty blades and having a solidity strictly less than 1.0. The solidity is equal to a ratio between a chord at the blade tip and an inter-blade pitch at the blade tip. The fan section has a hub-tip ratio greater than or equal to 0.22 and less than or equal to 0.32, a pressure ratio greater than or equal to 1.05 and less than or equal to 1.5, and a peripheral speed at the blade tip greater than or equal to 260 m/s and less than or equal to 400 m/s. The pressure ratio and the peripheral speed are measured at cruising speed.