Gas Turbine Variable Vane Harmonic Drive for High-Torque Precision
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Legacy gas turbine engine variable vane systems face challenges in efficiently managing significant stress loads and forces, leading to inefficiencies in actuation due to robust mechanical linkages and hydraulic actuation systems.
Innovation Solution
The implementation of a harmonic drive system with a strain wave gearing mechanism, including a fixed circular spline, flex spline, and wave generator, coupled with an electric motor actuator, provides a compact, high-torque, and backlash-free gear ratio between 30:1 and 320:1, allowing precise control of variable vanes through a unison ring and sliding links.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If robust mechanical linkages and hydraulic actuation systems are used to handle significant stress loads on variable vanes, then the system can withstand high forces, but the device complexity and weight increase
Solution Approach 1:
The patent replaces the traditional hydraulic actuation system with an electric motor-driven harmonic drive system. The harmonic drive uses a strain wave gearing mechanism with a flex spline, circular spline, and wave generator to achieve high torque multiplication (30:1 to 320:1 gear ratio) in a compact package, eliminating the need for complex hydraulic components while maintaining force handling capability
Solution Approach 2:
The invention changes the actuation parameter from hydraulic pressure to electrical motor rotation, coupled with a high-ratio gear reduction. This parameter change allows the system to achieve the same force output with a simpler, more compact electric motor and harmonic drive assembly compared to hydraulic actuators
2Measurement precision
If traditional mechanical linkages are used to rotate variable vanes, then the system is simple in design, but the rotation precision and torque control are insufficient
Solution Approach 1:
The patent replaces simple mechanical linkages with a harmonic drive system that provides precise rotational control through strain wave gearing. The flex spline's elastic deformation and meshing with the circular spline create a backlash-free transmission mechanism that delivers both high precision rotation and high torque capability simultaneously
Solution Approach 2:
The harmonic drive utilizes curved, flexible splines instead of straight mechanical linkages. The flex spline's elastic curvature allows for smooth, precise rotational motion while the distributed tooth contact across the curved surfaces enables high torque transmission without the limitations of rigid mechanical linkages
3Power
If high gear ratio (30:1 to 320:1) is achieved to increase torque and reduce rotation requirements, then the torque output increases significantly, but the device complexity increases
Solution Approach 1:
The patent achieves high gear ratios using a harmonic drive with strain wave gearing instead of traditional multi-stage planetary or spur gear systems. The harmonic drive accomplishes 30:1 to 320:1 reduction in a single stage through the elastic deformation of the flex spline, reducing the number of gear stages and overall system complexity while maintaining high torque output
Solution Approach 2:
The harmonic drive components are nested within each other - the flex spline is inserted over the wave generator, which is positioned within the circular spline. This nested arrangement achieves high gear ratio in a compact, integrated package without requiring multiple separate gear stages, thereby reducing device complexity while maintaining high torque capability
4Weight of moving object
If compact and lightweight design is prioritized for the variable vane system, then the system weight is reduced, but the force handling capability may be compromised
Solution Approach 1:
The patent replaces heavy hydraulic actuators and robust mechanical linkages with a lightweight electric motor and harmonic drive system. The strain wave gearing mechanism transmits high forces through elastic deformation of the flex spline and distributed tooth contact, enabling the system to handle significant stress loads with much lighter components than traditional hydraulic systems
Solution Approach 2:
The invention changes from hydraulic force transmission to electric motor rotation with high-ratio gear reduction. This parameter change allows the use of lightweight electric motors instead of heavy hydraulic pumps and actuators, while the harmonic drive's elastic mechanics enable compact, lightweight construction that still handles significant aerodynamic forces on the variable vanes
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 solution enhances the operational efficiency of gas turbine engines by reducing rotation requirements, increasing torque, and preventing back-driving from aerodynamic forces, while maintaining compactness and light weight, thereby improving the variable vane system's performance and stability.
Implementation Method 1
a strain wave gearing mechanism, including a fixed circular spline, flex spline, and wave generator, the flex spline driven by the wave generator with respect to the circular spline
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A variable vane system includes an actuator, a harmonic drive, a unison ring (306) and a multiple of variable vanes. The harmonic drive is driven by the actuator. The unison ring (306) is driven by the harmonic drive and includes a multiple of pins (304). The multiple of variable vanes is driven by the unison ring (306) and each of the vanes is connected to the unison ring (306) through a drive arm (300) including a slot which receives one of the pins (304) to accommodate axial motion of the unison ring (306).