Aircraft Pylon Cutout for Propeller Wake Noise Reduction

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Solution Overview

Problem

Conventional turbojet engines with unducted propellers face significant noise issues due to interactions between the wake created by the attachment pylon and the upstream propeller, leading to tonal and broadband noise, which existing solutions often address at the cost of engine performance by requiring active systems that divert engine air.

Innovation Solution

A propulsion assembly featuring an attachment pylon with a cutout in its trailing edge, extending transversely between the leading and trailing edges, which reduces the size of the wake and increases the distance for wake dissipation before encountering the propeller, thereby reducing noise passively without affecting engine performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If an active system with tiltable faces and air blowing is used to compensate for wake speed deficit, then noise from propeller-wake interaction is reduced, but engine performance is reduced due to large air consumption under pressure

Engineering Contradiction:

Improvenoise from propeller-wake interactionVSAvoidengine performance

Core Design Contradiction:

Object-affected harmful factorsVSLoss of energy

Solution Approach 1:

The invention extracts the problematic wake generation mechanism by removing the solid portion of the pylon trailing edge through the cutout. This eliminates the source of wake-speed deficit interaction with the propeller, reducing noise without requiring active air blowing systems that would consume engine performance

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention converts the harmful wake interaction into a beneficial effect by using the cutout to allow the propeller to operate in cleaner airflow. The cutout transforms the pylon from a noise-generating obstacle into an aerodynamic feature that reduces wake interference, achieving noise reduction passively without energy loss

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Device complexity

If a conventional pylon without cutout is used, then structural simplicity is maintained, but noise from wake-propeller interaction increases due to speed deficit downstream

Engineering Contradiction:

Improvepylon structureVSAvoidnoise from wake-propeller interaction

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The invention applies local quality modification by introducing a cutout only at the trailing edge portion of the pylon that faces the propeller. This localized change affects only the critical interaction zone between the pylon wake and propeller blades, reducing noise while preserving the overall simplicity and structural integrity of the pylon

Inventive Principle:

Principle #3Local quality

3Object-affected harmful factors

If the distance between pylon trailing edge and propeller is increased, then wake-propeller interaction noise is reduced, but the overall pylon size and material usage increase

Engineering Contradiction:

Improvewake-propeller interaction noiseVSAvoidpylon weight

Core Design Contradiction:

Object-affected harmful factorsVSWeight of moving object

Solution Approach 1:

The invention uses a curved outline for the cutout with at least two points of inflection, creating an optimized aerodynamic shape. This curvature allows the cutout to effectively increase the distance between the trailing edge and propeller while minimizing material removal and maintaining structural efficiency, reducing noise without excessive weight penalty

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 solution effectively decreases noise generated by the interaction between the wake and the propeller, optimizing noise reduction at the propeller tips while maintaining engine efficiency and reducing material usage for weight savings.

Implementation Method 1

the interaction between the upstream propeller and the wake created downstream from the pylon

Methodology Applied

Scientific EffectWake: Turbulence

Data Source

PatentUS10723434B2Aircraft propulsion unit comprising an unducted-fan turbine engine and an attachment pylon

Publication Date: 2020.07.28 SAFRAN AIRCRAFT ENGINES SAS

AI summary

A propulsion assembly for aircraft, the assembly including a turbojet having at least one unducted propulsion propeller; and an attachment pylon for attaching the turbojet to a structural element of the aircraft, the pylon being positioned on the turbojet upstream from the propeller and having an airfoil extending transversely between a leading edge and a trailing edge, the trailing edge of the airfoil of the pylon includes a cutout extending longitudinally over a fraction of the trailing edge facing at least a portion of the propeller, the cutout being configured to increase locally the distance between the trailing edge and the propeller, the cutout presenting an outline having a curved shape presenting at least two points of inflection.