Axially Symmetrical Trailing Edge Rotor Blade Design

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Solution Overview

Problem

Rotorcraft blades experience suboptimal aerodynamic behavior at high forward speeds due to increased forces required for pitch control and aerodynamic stall, particularly within the inversion circle, leading to reduced flight quality and potential tail-shake phenomena.

Innovation Solution

A method of manufacturing rotor blades with axially symmetrical trailing edge sections for the blade root, neck, and central profiled zone, ensuring consistent aerodynamic performance regardless of airflow direction, which reduces turbulent airflow and drag within the inversion circle, thereby improving lift and reducing control forces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional rotor blades with asymmetric profiles are used, then aerodynamic performance is optimized for standard flight conditions, but aerodynamic behavior deteriorates at high forward speeds within the inversion circle

Engineering Contradiction:

Improveaerodynamic performanceVSAvoidperformance consistency across flight conditions

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent applies asymmetry in reverse - it uses axial symmetry in the trailing edge section to solve an asymmetry problem. Conventional blades have asymmetric profiles optimized for one airflow direction, but the invention makes the trailing edge section axially symmetric so that the blade performs consistently whether airflow moves from leading to trailing edge or vice versa within the inversion circle

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent applies local quality by modifying only the trailing edge section of the blade profile while keeping the leading edge section unchanged. This localized modification to the trailing edge creates axial symmetry without redesigning the entire blade, allowing the blade to maintain consistent aerodynamic behavior in both forward and reverse airflow conditions

Inventive Principle:

Principle #3Local quality

2Speed

If rotor blades operate within the inversion circle at high forward speeds, then forward speed is achieved, but control forces increase and aerodynamic stall occurs

Engineering Contradiction:

Improveforward speedVSAvoidpitch control force

Core Design Contradiction:

SpeedVSForce

Solution Approach 1:

The patent changes the geometric parameter of the trailing edge section to create axial symmetry. This parameter change in the blade profile geometry fundamentally alters the aerodynamic characteristics, allowing the blade to maintain stable lift and reduced drag even when operating within the inversion circle at high forward speeds

Inventive Principle:

Principle #35Parameter changes

3Loss of energy

If asymmetric blade profiles are used, then aerodynamic efficiency is maximized for conventional flight, but turbulent airflow and drag increase within the inversion circle

Engineering Contradiction:

Improveaerodynamic dragVSAvoidairflow stability

Core Design Contradiction:

Loss of energyVSStability of the object's composition

Solution Approach 1:

The patent uses axial symmetry in the trailing edge section to stabilize airflow. By making the trailing edge section axially symmetric, the blade maintains consistent aerodynamic properties regardless of airflow direction, preventing turbulent flow and reducing drag within the inversion circle

Inventive Principle:

Principle #4Asymmetry

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 method enhances aerodynamic performance and reduces control forces during high-speed flights by maintaining consistent lift and minimizing drag within the inversion circle, improving overall rotorcraft stability and flight quality.

Implementation Method 1

determination of a trailing edge section of each profile for the blade root, the blade neck and a central part of the profiled zone by axial symmetry of the leading edge section

Methodology Applied

Scientific EffectAerodynamic symmetry:

Implementation Method 2

reduces turbulent airflow and drag within the inversion circle

Methodology Applied

Scientific EffectTurbulent airflow reduction: Turbulence

Implementation Method 3

This flow of air thus sweeps each blade from its leading edge to its trailing edge, which generates aerodynamic forces, in particular an aerodynamic lift force making it possible at least to sustain the rotorcraft

Methodology Applied

Scientific EffectAerodynamic lift: Aerofoil

Data Source

PatentEP3925875B1Method for constructing a rotor blade intended for a rotorcraft, blade and rotorcraft

Publication Date: 2023.07.05 EUROCOPTER FRANCE SA

Figure 1
Figure 2
Figure 3~4

AI summary

The present invention relates to a blade whose aerodynamic profiles (11) of a blade root, a blade throat, and a central portion of a profiled area of said blade respectively comprise a leading edge section (15) and a trailing edge section (16) that are symmetrical to each other with respect to an axis of symmetry. The present invention also relates to a method of constructing such a blade. Said axis of symmetry is perpendicular to a segment (s) connecting the leading edge (5) to the trailing edge (6) of each profile (11) and is positioned at the midpoint of said segment (s). An intermediate upper surface section (171) and an intermediate lower surface section (181) connect said leading edge section (15) and said trailing edge section (16) to form respectively an lower surface (18) of said aerodynamic profile (11).