Rotor Hub Cap Aerodynamic Profile Design
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Solution Overview
Problem
Conventional cupolas for rotorcraft lift rotors are not optimized to reduce aerodynamic excitations and frequency signatures, leading to discomfort, equipment fatigue, and operational issues due to disturbed airflow and vortex generation.
Innovation Solution
A cupola with a crenellated cap extending radially from the axis of rotation, featuring aerodynamic profiles with variable thickness, rounded leading and trailing edges, and specific curvature radii, designed to deflect airflow downward and minimize separation, thereby reducing aerodynamic drag and wake intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional cupola is used to deflect airflow downstream of the lift rotor, then the tail-shake effect is reduced, but the aerodynamic flow separation still occurs downstream of the engine cowls generating vortices and increasing aerodynamic excitations
Solution Approach 1:
The patent applies curvature to the cupola structure by defining an aerodynamic profile with rounded leading and trailing edges instead of sharp corners. The profile includes a rounded leading edge with a first radius of curvature and a rounded trailing edge with a second radius of curvature, creating a smooth, curved surface that guides airflow continuously and prevents flow separation downstream of the engine cowls.
Solution Approach 2:
The patent changes the geometric parameters of the cupola by introducing variable thickness along the aerodynamic profile and specific curvature radii for the leading and trailing edges. These parameter modifications transform the conventional sharp-edged cupola into an optimized aerodynamic shape that reduces wake intensity and minimizes aerodynamic excitations on stabilizing surfaces.
2Object-affected harmful factors
If the cupola is sized to deflect aerodynamic flow and minimize separation, then the tail-shake is reduced, but the frequency signature of aerodynamic forces cannot be controlled
Solution Approach 1:
The patent enables frequency signature control by introducing adjustable geometric parameters including the first radius of curvature of the leading edge, the second radius of curvature of the trailing edge, and the variable thickness distribution along the profile. These parameters can be optimized to control the aerodynamic forces and their frequency signature while maintaining flow attachment.
3Ease of manufacture
If a conventional cupola with sharp edges is used, then the structure is simple to manufacture, but the aerodynamic drag and wake intensity are increased
Solution Approach 1:
The patent replaces sharp edges with curved surfaces defined by specific radius of curvature values for the leading and trailing edges. This curvature transformation reduces aerodynamic drag and wake intensity by eliminating flow separation points, while the defined geometric parameters maintain manufacturing feasibility through standardized aerodynamic profile design.
4Ease of manufacture
If the cupola has constant thickness, then the manufacturing is simplified, but the aerodynamic performance and flow deflection efficiency are suboptimal
Solution Approach 1:
The patent optimizes aerodynamic performance by implementing variable thickness along the aerodynamic profile rather than constant thickness. The thickness varies according to a defined distribution that enhances flow deflection efficiency and reduces wake intensity, while the overall geometric framework remains suitable for manufacturing processes.
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 optimized cupola design reduces the intensity of aerodynamic excitations on stabilizing surfaces, limits airflow separation, and decreases the frequency signature of aerodynamic forces, enhancing crew comfort and rotorcraft system operation.
Implementation Method 1
the cupola deflects the airflow downstream of the lift rotor downwards
Implementation Method 2
a separation of the air flow over the cell can occur downstream of a lift rotor, in particular downstream of engine cowlings
Data Source
Figure 1~2
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Figure 5~6
AI summary
The present invention relates to a dome (20) intended for a rotor (14) of a rotorcraft (10), said dome (20) comprising a cap (25) extending radially from an axis of rotation in elevation (100) towards a periphery (27) and in azimuth over 360 degrees, said cap (25) extending in thickness between an inner face (31) intended to be opposite a hub (18) of said rotor (14) and an outer face (32) overhanging said inner face (31), said periphery (27) being crenellated to define a succession of slots (28) and cells (29), each cell (29) allowing the flapping movement of a blade (19) of said rotor (14).