Rotor Hub Convex Upper Surface Drag Reduction

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Solution Overview

Problem

Conventional rotary-wing aircraft face limitations in maximum flight speed due to high drag, particularly from the rotor hub, which contributes 25%-30% to total drag, leading to reduced efficiency and increased fuel burn.

Innovation Solution

A redesigned rotor hub with a convex upper surface and flat bottom surface minimizes flow separation and stagnation regions, reducing drag by maintaining attached flow and eliminating backward-facing ramps, while maintaining a rounded edge to avoid adverse effects at high angles of attack.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a conventional rotor hub design is used, then the structural integrity is maintained, but the drag is high (contributing 25%-30% to total drag)

Engineering Contradiction:

ImprovedragVSAvoidstructural integrity

Core Design Contradiction:

Object-affected harmful factorsVSStrength

Solution Approach 1:

The rotor hub is redesigned with a curved upper surface instead of a flat surface, creating a more aerodynamic, rounded shape that reduces flow separation and drag while maintaining structural integrity through the curved geometry

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Speed

If the rotor hub speed is increased to improve flight speed, then the maximum flight speed is limited by drag

Engineering Contradiction:

Improveflight speedVSAvoiddrag

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The curved upper surface of the rotor hub creates a more aerodynamic profile that reduces drag, allowing the aircraft to achieve higher flight speeds by minimizing the harmful drag effect that previously limited speed increases

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Ease of manufacture

If a flat upper surface is used on the rotor hub, then the manufacturing is simpler, but flow separation and stagnation regions occur

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidflow separation

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The curved upper surface replaces the flat surface to eliminate flow separation and stagnation regions, with the rounded geometry guiding airflow smoothly over the hub while maintaining manufacturability through standard curvature radii

Inventive Principle:

Principle #14Spheroidality (Curvature)

4Strength

If the hub thickness is increased to maintain structural strength, then the drag increases due to larger surface area

Engineering Contradiction:

Improvehub strengthVSAvoiddrag

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The curved upper surface with optimized radius creates a more aerodynamic profile that reduces drag, allowing the hub to maintain structural strength with reduced thickness by distributing stresses through the curved geometry rather than relying on increased thickness

Inventive Principle:

Principle #14Spheroidality (Curvature)

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 new hub design reduces drag, enabling a 5-knot (2.6 m/s) increase in maximum flight speed and minimizing fuel burn, as confirmed by Computational Fluid Dynamics simulations.

Implementation Method 1

minimizes flow separation and stagnation regions, reducing drag by maintaining attached flow

Methodology Applied

Scientific EffectFlow separation: Flow Separation

Data Source

PatentEP3693267B1Low drag hub for rotor

Publication Date: 2022.09.21 SIKORSKY AIRCRAFT CORP

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AI summary

A rotor assembly includes a first rotor hub (36) and a second rotor hub (39). The second rotor hub (39) is coupled to the first rotor hub (36) via a shaft fairing (44). The first rotor hub (36) has a flat first surface (308) coupled to the shaft fairing and a curved second surface opposite (302) the flat first surface. The second rotor hub has a flat first surface on the lower side and a curved second surface opposite the flat first surface.