Variable Pitch Fan Blade Geared Architecture for Gas Turbine Flutter
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Solution Overview
Problem
Gas turbine engine fan sections experience self-induced oscillations, such as flutter, which can lead to airfoil fracture, and increasing chord width to prevent this increases engine weight and rotating mass.
Innovation Solution
A geared architecture is introduced to drive the fan section at a different speed than the turbine section, with a fixed area fan nozzle and adjustable pitch fan blades to reduce flutter and weight, while maintaining thrust performance across varying operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the chord width of fan blades is increased to prevent flutter and fracture, then the reliability and structural integrity are improved, but the weight of the engine and rotating mass increase
Solution Approach 1:
The patent changes the operating parameters of the fan system by introducing a geared architecture that allows the fan to rotate at a different speed than the turbine, thereby changing the aerodynamic conditions and reducing flutter without requiring increased blade chord width or weight
Solution Approach 2:
The patent introduces variable pitch capability to the fan blades, allowing the blade angle to be dynamically adjusted during operation. This dynamic adjustment optimizes aerodynamic performance and reduces flutter across different operating conditions without increasing structural weight
2Weight of moving object
If the fan rotates at a slower speed to reduce flutter and weight, then the weight and aerodynamic losses are decreased, but the thrust generation capability may be reduced
Solution Approach 1:
The geared architecture changes the speed parameter relationship between the turbine and fan, allowing the fan to rotate at an optimized slower speed while the turbine operates at its optimal higher speed, thereby maintaining power generation capability while reducing fan-induced flutter and weight
Solution Approach 2:
Variable pitch control dynamically adjusts the blade angle to optimize thrust generation at the reduced fan speed, ensuring that the slower rotating fan can still produce adequate thrust across different operating conditions without requiring excessive weight
3Adaptability or versatility
If a variable area fan nozzle is used to maintain thrust performance at varying speeds, then the adaptability is improved, but the device complexity and weight increase
Solution Approach 1:
Instead of varying the nozzle area, the patent varies the fan blade pitch angle and rotational speed through the geared architecture, achieving adaptability to different operating conditions through parameter changes in the rotating components rather than the nozzle structure
Solution Approach 2:
Rather than making the nozzle variable to achieve adaptability, the patent inverts the approach by making the fan blades variable (pitch control) and the speed relationship variable (geared architecture), thereby achieving the same adaptability goal through a different component
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 solution effectively reduces flutter and weight by allowing the fan section to operate at a slower speed, decreasing aerodynamic losses and enabling efficient thrust generation over a wider range of conditions without the need for a variable area fan nozzle, thus enhancing engine compactness and power density.
Implementation Method 1
A geared architecture is in communication with the fan and driven by a turbine section. The fan rotates at a first speed and the turbine section rotates at a second speed different from the first speed
Implementation Method 2
The fan section includes multiple airfoils disposed circumferentially about an engine longitudinal centerline axis
Implementation Method 3
The high-speed exhaust gas flow expands through the turbine section to drive the compressor and the fan section
Data Source
AI summary
A gas turbine engine according to an exemplary aspect of the present disclosure includes, among other things, a fan section including a fan rotatable about an engine axis with a plurality of fan blades rotatable about a fan blade axis. A geared architecture is in communication with the fan and driven by a turbine section. The fan rotates at a first speed and the turbine section rotates at a second speed different from the first speed and a fixed area fan nozzle in communication with the fan section.