Teetering Propulsor Assembly for eVTOL Vibration Relief
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Solution Overview
Problem
Aircraft propulsor assemblies experience vibration and unsteady pressure fields during edgewise flight conditions, particularly when transitioning between vertical and forward flight modes, due to asymmetric interactions on the advancing and retreating sides of the blades, affecting operational stability and durability.
Innovation Solution
A propulsor assembly with a monolithic blade and a teeter mechanism that allows for passive teetering or flapping, reducing vibration by allowing up-and-down tip displacement of the blade, which is coupled to a power source via a coupling assembly including a yoke, bearings, and brackets with biasing members to maintain pivoting within a preset range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the propulsor assembly uses a fixed blade structure, then the manufacturing precision and structural simplicity are improved, but vibration and operational stability deteriorate during edgewise flight conditions
Solution Approach 1:
The blade is transformed from a fixed structure to a dynamic one by introducing a teeter mechanism that allows the blade to pivot about a teeter axis. This enables the blade to adapt its orientation in response to edgewise flight conditions, reducing vibration and improving operational stability during transition between vertical and forward flight modes.
Solution Approach 2:
The blade's operational parameters are changed by allowing it to rotate about a teeter axis, introducing an additional degree of freedom. This parameter change enables the blade to adjust its angle of attack dynamically, transforming the harmful edgewise forces into beneficial pitch variations that reduce vibration.
2Reliability
If the propulsor assembly allows blade displacement to reduce vibration, then operational stability is improved, but device complexity increases due to the teeter mechanism
Solution Approach 1:
The teeter mechanism is designed to operate passively, utilizing the natural forces acting on the blade during edgewise flight to drive the pivoting motion. The blade's own weight and aerodynamic forces provide the driving moment, eliminating the need for external actuators or complex control systems while still achieving vibration reduction.
Solution Approach 2:
A teeter mechanism serves as an intermediary between the blade and the airframe, absorbing and redistributing the edgewise forces. This intermediate mechanism translates the harmful lateral forces into beneficial pitch variations through passive pivoting, reducing vibration without requiring direct active control.
3Manufacturing precision
If the blade is rigidly coupled to the power source, then the manufacturing precision is improved, but the ability to absorb external forces deteriorates
Solution Approach 1:
The coupling between the blade and power source is segmented into two independent rotational degrees of freedom: one about the drive axis for power transmission, and another about the teeter axis for force absorption. This segmentation allows each degree of freedom to be optimized independently, maintaining manufacturing precision while enabling external force absorption.
Solution Approach 2:
The blade coupling is transformed from a rigid fixed connection to a dynamic mechanism that allows passive pivoting. This dynamic coupling absorbs external edgewise forces through the teetering motion, protecting the rigid blade structure and power source from harmful lateral loads while maintaining precise power transmission during normal operation.
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 teeter mechanism effectively reduces vibration and load on the propulsor assembly by absorbing external forces during edgewise flight, enhancing operational stability and durability.
Implementation Method 1
Aircraft propulsor assemblies experience vibration and unsteady pressure fields during edgewise flight conditions
Implementation Method 2
Coupling of the monolithic blade to a power source, such as a motor, and mounting on the teeter mechanism, may allow for passive teetering, or passive flapping, or passive deflection, of the monolithic blade
Implementation Method 3
a coupling assembly including a yoke, bearings, and brackets with biasing members to maintain pivoting within a preset range
Implementation Method 4
The teeter mechanism effectively reduces vibration and load on the propulsor assembly by absorbing external forces during edgewise flight
Data Source
AI summary
An electric vertical takeoff and landing aircraft including a teetering propulsor assembly is provided. The teetering propulsor assembly includes a propulsor, the propulsor including a monolithic blade including first and second blade portions extending radially outward from a hub, formed as a single unit. The coupling assembly includes a pair of torsional bearings coupled at the hub of the monolithic blade. The torsional bearings allow the monolithic blade to passively teeter in response to external forces applied to the propulsor, and exert a biasing, or centering, or restoring force on the monolithic blade that returns the monolithic blade to a neutral position. The torsional bearings may include an elastomeric member having relatively high stiffness, such as a high capacity laminate bearing.