Shaft Fairing De-rotation Using Toroidal CVT
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Solution Overview
Problem
The counter-rotating, coaxial rotor system in rotary wing aircraft experiences significant aerodynamic drag due to dual rotor hubs and the interconnecting main rotor shaft assembly, leading to a power penalty, especially at high speeds, and existing rotor hub fairing systems do not effectively address the drag generated by the exposed interconnecting main rotor shaft.
Innovation Solution
A de-rotation system incorporating a toroidal continuously variable transmission (CVT) is used to control the rotation of the shaft fairing, which includes a position control system with sensors and a controller to adjust the gear ratio of the CVT, preventing the shaft fairing from rotating freely and minimizing drag by positioning it optimally relative to the rotor axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a counter-rotating, coaxial rotor system is used to improve lift and stability, then aircraft performance is improved, but aerodynamic drag increases significantly due to dual rotor hubs and exposed shaft assembly
Solution Approach 1:
The shaft fairing is nested within the rotor hub fairing system, creating a hierarchical structure where the shaft fairing is positioned between the upper and lower rotor hubs. This nesting approach allows the fairing to streamline the exposed shaft assembly while maintaining the benefits of the counter-rotating coaxial rotor system.
Solution Approach 2:
The shaft fairing acts as an intermediary component that reduces aerodynamic drag by streamlining the flow around the interconnecting main rotor shaft assembly. The fairing mediates between the rotating shafts and the surrounding air, reducing turbulence and drag without interfering with the rotor system's operational effectiveness.
2Device complexity
If the shaft fairing is allowed to rotate freely with the shafts, then the structure remains simple, but aerodynamic drag increases and power penalty worsens
Solution Approach 1:
The de-rotation system dynamically controls the shaft fairing's rotational position using a continuously variable transmission (CVT). The system can adjust the fairing's rotation state in real-time, transitioning between rotating and stationary positions based on flight conditions, thereby optimizing aerodynamic performance while maintaining structural flexibility.
Solution Approach 2:
The patent replaces a traditional mechanical gear-based de-rotation system with a toroidal continuously variable transmission (CVT). This substitution eliminates the need for discrete gear shifts and provides smooth, continuous control over the shaft fairing's rotational speed and position, reducing mechanical complexity while improving aerodynamic efficiency.
3Object-generated harmful factors
If a de-rotation system with CVT is implemented to control shaft fairing rotation and reduce drag, then aerodynamic efficiency improves, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical gear systems with a toroidal continuously variable transmission (CVT), which provides smooth, continuous control over the shaft fairing's rotational speed. This substitution reduces the number of discrete components, eliminates gear shifts, and simplifies the overall mechanical architecture while maintaining precise control capability.
Solution Approach 2:
The de-rotation system is designed to perform multiple functions: controlling shaft fairing rotation, reducing aerodynamic drag, and adapting to various flight regimes. The CVT mechanism serves as a universal solution that can operate across different speed ranges and load conditions, consolidating what would otherwise require multiple specialized systems.
4Object-generated harmful factors
If position control sensors and controllers are added to optimize shaft fairing position, then drag reduction is improved, but device complexity and cost increase
Solution Approach 1:
The control system incorporates position sensors that continuously monitor the shaft fairing's angular position and provide feedback to the controller. This feedback mechanism enables the system to maintain the optimal fairing position by adjusting the CVT operation in real-time, ensuring maximum drag reduction while adapting to changing flight conditions.
Solution Approach 2:
The patent replaces complex mechanical position-locking mechanisms with an electronically controlled CVT system. The electronic control system uses sensors and actuators to achieve precise position control, eliminating the need for heavy mechanical locking devices and reducing overall system complexity while improving control precision.
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 de-rotation system effectively reduces aerodynamic drag by controlling the rotation of the shaft fairing, thereby minimizing power consumption and improving the efficiency of the rotary wing aircraft, especially at high speeds.
Implementation Method 1
A de-rotation system contained with the shaft fairing includes a toroidal continuously variable transmission configured to control the rotation of the shaft fairing about the first axis of rotation
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A fairing system for a rotary wing aircraft is provided including a shaft fairing mounted for rotation about a first axis of rotation. A de-rotation system contained with the shaft fairing includes a toroidal continuously variable transmission configured to control the rotation of the shaft fairing about the first axis of rotation. A position control system includes at least one position sensor and a controller. The at least one position sensor is configured to monitor a position of the shaft fairing relative to the first axis of rotation. The controller is operably coupled to the at least one position sensor and the de-rotation system. The controller is configured to adjust a gear ratio of the toroidal continuously variable transmission in response to a sensed position of the shaft fairing.