Aircraft Rear Thruster Stator Arms for Airflow Homogeneity

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Solution Overview

Problem

The propulsion system of aircraft with downstream fans is sensitive to air flow conditions, particularly orientation and homogeneity, leading to inefficiencies and noise pollution due to inhomogeneities and distortions in the air flow entering the nacelle.

Innovation Solution

The aircraft incorporates radial stator arms with variable-pitch mobile parts that pivot to axially deflect the air flow, ensuring homogeneous deflection and adaptive adjustment to flight conditions, along with blowing means to re-energize the air flow and reduce noise by minimizing the wake effect.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If the fans are positioned downstream of the fuselage to absorb the boundary layer, then noise and fuel consumption are reduced, but the propulsion system becomes sensitive to airflow inhomogeneities and distortions

Engineering Contradiction:

ImprovenoiseVSAvoidpropulsion system operability

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent applies preliminary action by introducing flow conditioning devices (swirl generators and flow straighteners) upstream of the fan rotor to pre-correct airflow distortions before they reach the sensitive propulsion system. This preliminary flow conditioning ensures homogeneous airflow enters the fan, maintaining reliability while preserving the downstream fan configuration that reduces noise.

Inventive Principle:

Principle #10Preliminary action

2Object-affected harmful factors

If the fan rotational speed is reduced to maintain subsonic blade tip speed, then noise is reduced, but thrust generation efficiency decreases

Engineering Contradiction:

ImprovenoiseVSAvoidthrust

Core Design Contradiction:

Object-affected harmful factorsVSPower

Solution Approach 1:

The patent applies parameter changes by optimizing the fan blade geometry (pitch angle, chord length distribution) and operating parameters (pressure ratio, flow coefficient) to achieve efficient thrust generation at lower rotational speeds. The variable pitch blades allow optimization of the angle of attack across different operating conditions, maintaining high efficiency while operating below sonic speeds to reduce noise.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If radial stator arms with movable flaps are added to correct airflow inhomogeneities, then propulsion system efficiency is improved, but device complexity increases

Engineering Contradiction:

Improvepropulsion system efficiencyVSAvoidnacelle structure

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent applies segmentation by dividing the flow correction function into multiple independent components: swirl generators at the inlet to remove rotational components, followed by flow straighteners with adjustable flaps to correct inhomogeneities. Each segment addresses a specific aspect of flow conditioning, making the overall system more manageable and efficient while distributing the complexity across modular elements.

Inventive Principle:

Principle #1Segmentation

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 solution improves the operability and efficiency of the propulsion system by correcting air flow inhomogeneities, reducing noise pollution, and maintaining low rotation speeds while maintaining significant thrust.

Implementation Method 1

said radial arms comprising at least one movable part with variable pitch configured to axially deflect said airflow

Methodology Applied

Scientific EffectFlow deflection:

Implementation Method 2

blowing means configured to blow, in an environment of a trailing edge of said radial arms, an additional airflow adding to said airflow in an extension of the trailing edge

Methodology Applied

Scientific EffectWake reduction:

Data Source

PatentEP3325346B1Aircraft including a streamlined rear thruster with an input stator having movable flaps

Publication Date: 2023.03.22 SAFRAN AIRCRAFT ENGINES SAS

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Figure 3~5
Figure 6~8b

AI summary

The invention relates to an aircraft including a fuselage (1) and a propulsion assembly. Said propulsion assembly includes at least one fan rotor (7, 8) placed behind the fuselage (1) as an extension thereof along a longitudinal axis (XX), and a nacelle (14) which forms a fairing of said at least one fan rotor (7, 8) through which at least one air flow (F) passes. Said aircraft is characterized in that it comprises a plurality of stator radial arms (15) mounted upstream of said at least one fan rotor (7, 8) and extending between the fuselage (1) and the nacelle (14). Said radial arms (15) comprise at least one variable-pitch movable portion (16) configured to axially divert said air flow (F).