Unducted Aircraft Thruster with Segmented Variable-Pitch Stator Blades

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Solution Overview

Problem

Unducted turbomachines with annular rows of upstream rotor blades and downstream stator blades face issues with increased noise levels due to the absence of fairing, and unsatisfactory thrust during take-off and landing phases due to non-axisymmetric acoustic radiation and heterogeneous aerodynamic loads on the downstream stator blades.

Innovation Solution

The proposed aeronautical thruster features an annular row of unducted upstream rotor blades and an annular row of unducted downstream stator blades, where the downstream stator blades are categorized into two types: one with fixed pitch and the other with variable pitch. The variable-pitch downstream stator blades can be adjusted based on the operational phase and local airflow conditions to reduce noise and improve aerodynamic performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If downstream stator blades have fixed pitch, then manufacturing is simpler and structural integrity is maintained, but aerodynamic performance and noise reduction are insufficient during critical phases

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidaerodynamic performance

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

The downstream stator blades are segmented into two distinct types: first type blades with fixed pitch for structural simplicity and manufacturing ease, and second type blades with variable pitch for optimized aerodynamic performance. This segmentation allows each blade type to serve its specific functional purpose, resolving the contradiction between manufacturing simplicity and aerodynamic performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different sections of the downstream stator blade assembly have different pitch characteristics. The first angular sector contains blades with fixed pitch optimized for structural integrity, while the second angular sector contains blades with variable pitch optimized for aerodynamic performance and noise reduction. This local differentiation of quality allows the system to achieve both manufacturing simplicity and high aerodynamic performance simultaneously.

Inventive Principle:

Principle #3Local quality

2Productivity

If all downstream stator blades have variable pitch, then aerodynamic performance and noise reduction are improved, but device complexity and manufacturing difficulty increase

Engineering Contradiction:

Improveaerodynamic performanceVSAvoidstructural complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

Instead of making all downstream stator blades variable pitch, the system segments the blade array into two types with different pitch characteristics. This reduces overall structural complexity while maintaining variable pitch capability where needed for optimized aerodynamic performance during critical phases.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Variable pitch capability is applied locally only to the second type of downstream stator blades positioned in the second angular sector, rather than uniformly across all blades. This localized application of complexity provides aerodynamic optimization where most needed while minimizing overall device complexity and manufacturing difficulty.

Inventive Principle:

Principle #3Local quality

3Productivity

If downstream stator blades are positioned to maximize thrust, then productivity improves, but noise levels increase due to non-axisymmetric acoustic radiation

Engineering Contradiction:

Improvethrust efficiencyVSAvoidnoise levels

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The system deliberately introduces asymmetry in the downstream stator blade configuration by positioning different blade types in different angular sectors. The first angular sector contains fixed-pitch blades while the second angular sector contains variable-pitch blades, creating a non-uniform distribution that optimizes thrust while managing noise through controlled asymmetric acoustic radiation patterns.

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

This configuration reduces noise levels and enhances the aerodynamic performance of the downstream stator blades, ensuring improved thrust efficiency during critical phases like take-off and landing.

Implementation Method 1

each downstream stator blade of the second type having a variable pitch

Methodology Applied

Scientific EffectAerodynamic performance: Aerofoil

Implementation Method 2

The annular row of upstream rotor blades and the annular row of downstream stator blades define an upstream propeller and a downstream propeller respectively

Methodology Applied

Scientific EffectThrust generation: Aerofoil

Data Source

PatentUS20250188951A1Propulsion system for an aircraft

Publication Date: 2025.06.12 SAFRAN AIRCRAFT ENGINES SAS

AI summary

An aeronautical thruster of longitudinal axis includes a hub, an annular row of unducted upstream rotor blades, and an annular row of unducted downstream stator blades. The annular row of downstream stator blades includes at least one downstream stator blade of a first type, each of which is located about the longitudinal axis in a first angular sector about the longitudinal axis. Each downstream stator blade of the first type has a fixed pitch. The annular row of downstream blades further includes at least one downstream stator blade of a second type, each of which is located about the longitudinal axis outside said first angular sector, wherein each downstream stator blade of the second type has a variable pitch.