Fan Blade Tip Angle Optimization for Bird Strike Resistance
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Solution Overview
Problem
Modern gas turbine engines face challenges in balancing efficiency, weight, and the capability to withstand bird strikes, often requiring heavier and more complex fan systems to absorb the impact, which compromises other design aspects.
Innovation Solution
The design incorporates a fan with a specific fan tip air angle (57-62 degrees) and fan blade tip angle (57-65 degrees) to direct bird strikes to the leading edge, which is stronger than the pressure or suction surfaces, combined with a gearbox that reduces fan rotational speed, enhancing efficiency and reducing the need for heavy or complex solutions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fan system is made heavier and more robust to withstand bird strikes, then the bird strike resistance is improved, but the engine weight and complexity increase
Solution Approach 1:
The patent changes the geometric parameters of the fan blade, specifically setting the fan blade tip angle β between 57-65 degrees and the fan tip air angle θ between 57-62 degrees at cruise conditions. These parameter changes optimize the blade geometry to direct bird strikes to the leading edge, improving bird strike resistance without increasing weight or complexity
Solution Approach 2:
Instead of making the fan blade stronger to resist bird strikes, the patent inverts the approach by designing the blade geometry to direct the bird strike to the leading edge, where the blade is naturally stronger. This uses the existing structural strength rather than adding more material
2Reliability
If the fan system is made heavier and more robust to withstand bird strikes, then the bird strike resistance is improved, but the device complexity increases
Solution Approach 1:
The patent optimizes the fan blade geometry parameters (tip angle β and tip air angle θ) within specific ranges to achieve bird strike resistance through geometric optimization rather than structural reinforcement, avoiding increased device complexity
Solution Approach 2:
The patent inverts the conventional approach of reinforcing the fan blade structure and instead uses geometric configuration to direct bird strikes to the naturally stronger leading edge, maintaining simplicity while improving reliability
3Loss of energy
If the fan rotational speed is reduced to improve efficiency, then the engine efficiency is improved, but the bird strike resistance may be compromised
Solution Approach 1:
The patent changes the fan blade angle parameters to optimize performance at lower rotational speeds, allowing the engine to operate more efficiently while maintaining bird strike resistance through geometric optimization rather than speed-dependent dynamic characteristics
Solution Approach 2:
Instead of relying on high rotational speed for bird strike resistance, the patent inverts the approach by using optimized blade geometry to direct strikes to the leading edge, enabling efficient low-speed operation without compromising reliability
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 configuration improves the engine's ability to withstand bird strikes with minimal compromise on other design aspects, allowing for a lighter, less complex, and more efficient fan system with improved aerodynamic design freedom.
Implementation Method 1
a fan tip air angle θ is in the range: 57 degrees≤θ≤62 degrees, the fan tip air angle θ being defined as: tanθ=Vxair/VThetaBladeTip where ω is fan rotational speed in radians/second; D is the diameter of the fan in meters at its leading edge; and Vxair is the mean axial velocity of the flow into the fan over the leading edge
Data Source
AI summary
A gas turbine engine has a fan tip air angle and/or a fan blade tip air angle in a defined range to achieve improved over all performance, taking into account fan operability and/or bird strike requirements as well as engine efficiency. The defined ranges of fan tip air angle and/or a fan blade tip air angle may be particularly beneficial for gas turbine engines in which the fan is driven by a turbine through a gearbox.