Harmonic Drive Cable System for Gas Turbine Variable Vanes
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Solution Overview
Problem
Legacy gas turbine engine variable vane systems face challenges in efficiently rotating variable vanes due to significant stress loads and forces, often relying on robust mechanical linkages and hydraulic actuation, which can be cumbersome and inefficient.
Innovation Solution
A variable vane system incorporating a harmonic drive mechanism with a strain wave gearing system, a cable drive system, and a unison ring, driven by an electric actuator, providing a high gear ratio (30:1-320:1) to efficiently rotate variable vanes with reduced backlash and increased torque, preventing back-driving by aerodynamic forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If legacy mechanical linkages and hydraulic actuation are used to rotate variable vanes, then the system can handle significant stress loads, but the device complexity and operational efficiency deteriorate
Solution Approach 1:
The patent replaces the legacy hydraulic actuation system with an electric motor-driven harmonic drive system. The harmonic drive mechanism (including wave generator, flex spline, and circular spline) provides robust torque transmission to handle significant stress loads while eliminating complex hydraulic components, thereby reducing overall device complexity and improving operational efficiency.
Solution Approach 2:
The patent introduces a cable drive system with drums as an intermediary mechanism between the harmonic drive output and the variable vanes. This cable-mediated transmission simplifies the mechanical linkage by replacing direct rigid connections with flexible cable drives, reducing complexity while maintaining the ability to transmit significant forces.
2Power
If high gear ratio (30:1-320:1) is provided through harmonic drive, then torque and precision are improved, but device complexity increases
Solution Approach 1:
The patent employs a harmonic drive mechanism that achieves high gear ratios (30:1-320:1) through a compact design involving a wave generator, flex spline, and circular spline. This replaces what would traditionally require multiple stages of conventional gearing, thereby providing high torque multiplication in a single, space-efficient mechanism that actually reduces overall system complexity despite the sophisticated gearing principle.
3Reliability
If robust mechanical linkages are used to prevent back-driving, then reliability is improved, but ease of operation and efficiency deteriorate
Solution Approach 1:
The patent uses the harmonic drive mechanism's inherent high gear ratio (30:1-320:1) and self-locking characteristics to prevent back-driving from aerodynamic forces. The wave generator and flexible spline design creates a mechanically locked state that prevents reverse motion without requiring additional robust mechanical linkages or over-center mechanisms, thereby maintaining ease of operation while ensuring 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
The solution enables precise and efficient rotation of variable vanes, improving operational performance and reducing the complexity of mechanical linkages, enhancing the overall efficiency and reliability of the gas turbine engine.
Implementation Method 1
A variable vane system incorporating a harmonic drive mechanism with a strain wave gearing system, a cable drive system, and a unison ring, driven by an electric actuator, providing a high gear ratio (30:1-320:1) to efficiently rotate variable vanes with reduced backlash and increased torque, preventing back-driving by aerodynamic forces.
Data Source
AI summary
A cable drive system for variable vane operation comprising an actuator, a harmonic drive driven by the actuator, a cable drive system driven by the harmonic drive; and a unison ring driven by the cable drive system.