Open Rotor Blade Pitch Scheduling for Cyclic Load Relief
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Solution Overview
Problem
Existing aircraft propulsion systems with open rotor configurations face challenges in efficiently managing blade and vane pitch adjustments to mitigate in-plane cyclic loading and enhance thrust performance.
Innovation Solution
Implementing an asymmetric blade and vane pitch schedule for the propulsor rotor and stator vane structure, where the pitch adjustments are angularly offset from the aircraft's pitch axis, and utilizing an actuation system to dynamically change blade and vane pitches during rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If symmetric blade pitch adjustment is used, then the structure is simple and easy to control, but the thrust performance and efficiency are reduced due to inability to optimize for in-plane cyclic loading
Solution Approach 1:
The patent applies asymmetric blade pitch adjustment where the pitch schedule is intentionally made non-uniform around the rotor circumference. The controller varies the pitch of individual blades or blade groups based on their angular position, creating an asymmetric pitch distribution that optimizes thrust performance and reduces in-plane cyclic loading effects, rather than using a uniform symmetric pitch adjustment.
Solution Approach 2:
The patent implements local quality by applying different pitch adjustments to different locations around the rotor. Each blade or blade group receives a customized pitch schedule tailored to its specific angular position and operational requirements, allowing optimization of thrust performance and load distribution at each local position rather than applying a uniform pitch change throughout.
2Productivity
If blade pitch is adjusted to maximize thrust, then thrust performance improves, but in-plane cyclic loading effects increase causing vibration and instability
Solution Approach 1:
The patent employs periodic action by implementing a cyclic pitch adjustment schedule that varies blade pitch periodically as the rotor rotates. The controller applies different pitch values to blades at different angular positions in a repeating pattern, which distributes the loading more evenly throughout the rotation cycle and reduces in-plane cyclic loading effects while maintaining thrust performance.
Solution Approach 2:
The patent applies preliminary action by proactively adjusting blade pitch before the rotor completes a full rotation cycle. The controller anticipates the rotational position and applies pitch adjustments in advance to optimize thrust while preventing excessive in-plane cyclic loading, rather than reacting to loading conditions after they occur.
3Stability of the object's composition
If asymmetric pitch schedule is applied to reduce in-plane cyclic loading, then stability improves, but control system complexity increases
Solution Approach 1:
The patent implements feedback by using the rotor's rotational position information to dynamically adjust blade pitch. The controller receives feedback about the angular position of each blade and applies appropriate pitch adjustments accordingly, creating a closed-loop control system that stabilizes the propulsion system while managing complexity through intelligent control algorithms.
Data Source
AI summary
A method is provided for operating an aircraft propulsion system. During this method, rotation of a propulsor rotor of the propulsion system is driven about a rotational axis. The propulsor rotor includes a plurality of rotor blades. A first blade pitch schedule is applied to the propulsor rotor while the propulsor rotor is rotating about the rotational axis such that: (a) a pitch of each of the rotor blades has a maximum blade pitch value when located at a first circumferential position about the rotational axis; (b) the pitch of each of the rotor blades has a minimum blade pitch value when located at a second circumferential position about the rotational axis; and (c) a reference line extending between the first circumferential position and the second circumferential position is angularly offset from a pitch axis of the aircraft by a first offset angle between zero degrees and forty-five degrees.