Bonded Acoustic Shroud Assembly for Aircraft Engine Casings

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Solution Overview

Problem

Existing turbomachine casings require complex and costly fastening systems for acoustic ferrules and abradable materials, which alter mechanical properties, introduce stress concentrations, and increase mass and manufacturing complexity.

Innovation Solution

A single-piece annular element combining acoustic attenuation and abradability, made of NIDA-type honeycomb material with a continuous body and a layer of abradable material, is manufactured and bonded to the casing, eliminating the need for separate components and mechanical connections.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a bolted fastening system is used to attach the acoustic ferrule to the casing, then the acoustic ferrule can be securely fixed, but the mechanical properties of the casing are altered and stress concentrations are introduced

Engineering Contradiction:

Improvefixing securityVSAvoidcasing mechanical properties

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The acoustic ferrule and abradable material support are merged into a single integral component that is directly bonded to the casing envelope. This eliminates the separate fastening system and its associated stress concentrations, while maintaining secure fixation through the bonding interface alone.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The mechanical bolted fastening system is replaced with a chemical bonding system. The acoustic ferrule assembly is attached to the casing envelope through adhesive bonding rather than mechanical fasteners, eliminating stress concentrations and preserving the mechanical properties of the casing.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If a bolted fastening system with connecting pieces is used, then the acoustic ferrule can be attached, but the device complexity and manufacturing cost increase

Engineering Contradiction:

Improveattachment securityVSAvoidfastening system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The acoustic ferrule and abradable material support are merged into a single integral component, eliminating the need for separate connecting pieces, L-shaped brackets, and multiple fasteners. This single-component approach dramatically simplifies the overall assembly and reduces manufacturing complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The complex bolted fastening system with multiple connecting pieces is completely extracted from the design. Only the essential acoustic ferrule component remains, attached directly to the casing through bonding, removing all unnecessary mechanical fastening elements.

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If grooves are machined in the acoustic ferrule for fastening, then the fastening system can be installed, but the acoustic properties and mechanical properties are altered

Engineering Contradiction:

Improvefastening capabilityVSAvoidacoustic and mechanical properties

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The grooves that were machined into the acoustic ferrule for fastening purposes are completely removed from the design. The integral acoustic ferrule component maintains its full acoustic and mechanical properties without any compromising geometric modifications.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The mechanical fastening approach requiring grooves is replaced with a bonding approach that does not require any geometric modifications to the acoustic ferrule. This preserves both the acoustic insulation properties and mechanical integrity of the component.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 reduces manufacturing costs, simplifies installation, enhances mechanical integrity and acoustic insulation, and decreases mass by eliminating stress concentrations and metal connections.

Implementation Method 1

an annular element, fixed on an inner surface of the envelope, the annular element comprising a body which is made of NIDA-type honeycomb material

Methodology Applied

Scientific EffectAcoustic absorption: Acoustic Absorption

Implementation Method 2

a downstream part having a first inner surface covered with a layer of abradable material

Methodology Applied

Scientific EffectAbrasion: Abrasion

Data Source

PatentEP4028645B1Attachment of an acoustic shroud to a housing shell for an aircraft turbine engine

Publication Date: 2026.03.25 SAFRAN AIRCRAFT ENGINES SAS

Figure 1~2A
Figure 2B
Figure 2C~2D

AI summary

The invention relates to a method for manufacturing an aircraft turbine engine housing, the housing (23) comprising: - an annular shell (29) with axis A; - an annular element (24; 253, 254) attached to the inside of the shell (29), the annular element comprising a body (25) made of NIDA-type cellular material and comprising a downstream portion (252) covered with an abradable material (26), and an upstream portion (251) without abradable material, the body (25) extending in a continuous manner from the upstream portion (251) to the downstream portion (252), the method comprising: - manufacturing the annular element in the form of a continuous annular body, - cutting the annular body into segments (253, 254), - attaching the segments to the shell, and - depositing the abradable material (26) onto the inside surface (25a) of the downstream portion (252).