Aircraft Fan Blade Solidity Optimization for Turbofan Efficiency
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Solution Overview
Problem
Modern turbofan engines face challenges in maximizing aerodynamic efficiency while maintaining adequate stability and stall margin, as high fan solidity is required for supersonic tip operation but can lead to inefficiencies and increased noise.
Innovation Solution
A turbofan design with a reduced number of fan blades (13 to 21) and a lower solidity ratio at specific radial locations, allowing for a lower blade count and increased circumferential pitch, which reduces flow blockage and improves aerodynamic efficiency while maintaining stability and stall margin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high fan solidity is used for supersonic tip operation, then aerodynamic efficiency is improved, but noise increases and manufacturing complexity increases
Solution Approach 1:
The patent changes the solidity parameter by reducing the number of blades from conventional high numbers to 13-21 blades, and by optimizing blade chord lengths and pitch distances. This parameter optimization allows the fan to operate efficiently at supersonic tip speeds while reducing noise generation, resolving the contradiction between aerodynamic efficiency and noise.
2Productivity
If high fan solidity is used for supersonic tip operation, then aerodynamic efficiency is improved, but device complexity increases
Solution Approach 1:
The patent optimizes the number of blades parameter, reducing it from conventional high numbers to a specific range of 13-21 blades. This parameter change simplifies the device while maintaining aerodynamic efficiency through optimized blade geometry and pitch distribution, resolving the contradiction between efficiency and complexity.
3Productivity
If high fan solidity is used for supersonic tip operation, then aerodynamic efficiency is improved, but manufacturing cost increases
Solution Approach 1:
The patent reduces manufacturing cost by optimizing the number of blades to 13-21 and adjusting blade chord lengths and pitch distances. This parameter optimization reduces material requirements and manufacturing complexity while maintaining aerodynamic efficiency, resolving the contradiction between efficiency and manufacturing cost.
4Device complexity
If reduced blade count is used, then device complexity is reduced, but flow blockage increases
Solution Approach 1:
The patent applies local quality optimization by varying the chord length of individual blades and optimizing the pitch distance between blades at different radial positions. This localized optimization ensures adequate flow passage area while maintaining the reduced blade count, resolving the contradiction between simplicity and flow blockage.
Solution Approach 2:
The patent changes the geometric parameters of the blades, specifically chord lengths and pitch distances, to compensate for the reduced number of blades. This parameter optimization maintains adequate flow area and reduces flow blockage while achieving the desired reduction in device complexity.
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
The design achieves increased aerodynamic efficiency and reduced engine weight and cost by lowering solidity and blade count, while maintaining stability and stall margin, particularly beneficial for large diameter transonic turbofans with supersonic tip airflow.
Implementation Method 1
each of the fan blades including an airfoil having circumferentially opposite pressure and suction sides extending radially in span from a root to a tip, and extending axially in chord between spaced-apart leading and trailing edges, with the airfoils defining corresponding flow passages therebetween for pressurizing air
Implementation Method 2
The blade tips are therefore subject to the generation of shock waves as the air is channeled and pressurized in the corresponding flow passages defined between adjacent fan blades
Data Source
AI summary
A fan for a gas turbine engine includes: an annular casing; a disk disposed inside the casing and mounted for rotation about an axial centerline, the disk including a row of fan blades extending radially outwardly therefrom; each of the fan blades including an airfoil having circumferentially opposite pressure and suction sides extending radially in span from a root to a tip, and extending axially in chord between spaced-apart leading and trailing edges, with the airfoils defining corresponding flow passages therebetween for pressurizing air; the row including no more than 21 and no less than 13 of the fan blades; and wherein each of the fan blades has a solidity defined by a ratio of the airfoil chord over a circumferential pitch of the fan blades, measured at 60% of a radial distance from the root to the tip, of less than about 1.6.