Harmonic Drive Variable Vanes to Prevent Back-Driving
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Solution Overview
Problem
Legacy gas turbine engine variable vane systems face challenges in efficiently managing significant forces and stress loads, particularly due to the mechanical linkage used to rotate robustly designed vanes, which can result in inefficiencies and limitations in operational performance.
Innovation Solution
The implementation of a harmonic drive system with a fixed circular spline, flex spline, and wave generator, along with electric motor actuators, provides a high gear ratio (30:1 - 320:1) to drive unison rings and variable vanes, minimizing backlash and maximizing torque while preventing back-driving by aerodynamic forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a mechanical linkage is used to rotate variable vanes, then the vanes can be positioned to change operational performance, but significant forces and stress loads are transmitted through the linkage reducing efficiency
Solution Approach 1:
The patent replaces the traditional mechanical linkage system with an electric actuator system. Each variable vane is equipped with an electric actuator that directly drives the vane rotation, eliminating the need for extensive mechanical linkages. This substitution reduces energy loss through mechanical transmission and improves overall system efficiency while maintaining full vane positioning capability.
Solution Approach 2:
The patent divides the variable vane system into independent controllable units, with each vane having its own electric actuator. This segmentation allows individual vane control without requiring a centralized mechanical linkage system, reducing energy transmission losses and enabling more efficient operation of each vane element independently.
2Strength
If robust variable vanes are designed to handle stress loads, then the vanes can withstand aerodynamic forces, but the mechanical linkage becomes more complex and less efficient
Solution Approach 1:
The patent replaces complex mechanical linkages with electric actuators that directly mount to each vane. This eliminates the need for complex intermediate linkages while maintaining the ability of robust vanes to withstand aerodynamic forces. The electric actuators provide direct drive capability, simplifying the overall system architecture.
Solution Approach 2:
The patent extracts and removes the mechanical linkage system from the variable vane mechanism, leaving only the essential electric actuator-vane direct connection. This extraction eliminates the complexity of mechanical linkages while preserving the strength and stress resistance capabilities of the robust vane design.
3Ease of operation
If traditional actuators are used to drive variable vanes, then the system can operate, but backlash and imprecise positioning occur
Solution Approach 1:
The patent replaces traditional mechanical actuators with electric actuators that offer precise control and minimal backlash. Electric actuators provide direct digital control of vane positioning, eliminating the backlash inherent in mechanical gear systems. This substitution maintains full system operability while dramatically improving positioning precision and control accuracy.
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 enhances the efficiency and stability of variable vane operation by reducing rotation and increasing torque, preventing back-driving, and allowing precise repositioning of inertial loads, thereby improving the overall performance and reliability of the gas turbine engine.
Implementation Method 1
Each harmonic drive includes a fixed circular spline, a flex spline attached to an output shaft, and a wave generator attached to an input shaft, the flex spline driven by the wave generator with respect to the circular spline.
Implementation Method 2
one or both of the first and second actuators is an electric motor
Data Source
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AI summary
An actuator system (118) including a harmonic drive (122) operable to drive a variable vane system (100) of a gas turbine engine (20).