Aircraft Engine Inlet Geometry for Boundary Layer Displacement

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Solution Overview

Problem

Existing aircraft designs struggle to efficiently deflect the boundary layer fluid away from the inlet opening of jet engines, resulting in lower energy air flow being ingested, which affects the performance of the jet engine.

Innovation Solution

The aircraft structure incorporates a compression surface, transition shoulder, and a flow guide surface as local elevations to deflect the boundary layer fluid away from the inlet opening, improving the energy of the air flow entering the engine.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If elevations or bumps are arranged on the outer surface to deflect the boundary layer away from the inlet opening, then the energy of the air flow entering the inlet opening is improved, but the device complexity increases

Engineering Contradiction:
Improveenergy of air flowVSAvoiddevice complexity
Core Design Contradiction:
Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The patent combines multiple surface features (elevation, bump, and flow guide surface) into a single integrated structure on the aircraft outer skin. This unified design achieves boundary layer deflection and flow guidance functions simultaneously, improving air flow energy while avoiding the complexity of separate components

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The flow guide surface is positioned specifically at the transition region between the elevation and the inlet opening, where it is most needed to guide the deflected boundary layer fluid away from the inlet. This localized placement optimizes the energy improvement while minimizing additional structural complexity

Inventive Principle:
Principle #3Local quality

2Power

If a larger inlet opening is used to receive high energy air flow, then the power of the jet engine is improved, but the area of the aircraft structure increases

Engineering Contradiction:
Improvepower of jet engineVSAvoidarea of aircraft structure
Core Design Contradiction:
PowerVSArea of stationary object

Solution Approach 1:

The elevation and flow guide surface are positioned upstream of the inlet opening to pre-deflect the boundary layer away from the inlet area before the air flow reaches it. This preliminary action ensures that high energy air is delivered to the inlet without requiring an oversized opening, thus maintaining engine power while controlling aircraft structure area

Inventive Principle:
Principle #10Preliminary action

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 enhances the energy of the air flow entering the jet engine, allowing for improved performance and potentially reducing the size of the inlet opening.

Implementation Method 1

the boundary layer of the flow, which is generated on the outer skin of the aircraft

Methodology Applied
Scientific EffectBoundary layer: Boundary Layer

Implementation Method 2

the compression surface (102) and the transition shoulder (104), which are arranged and designed to deflect a boundary layer of an air flow from the inlet opening

Methodology Applied
Scientific EffectDeflection:

Implementation Method 3

The air inlet furthermore has a flow guide surface, wherein the flow guide surface is arranged as a local elevation in a region of the transition shoulder and extends into the inlet opening

Methodology Applied
Scientific EffectFlow guidance:

Data Source

PatentEP4365085B1Aircraft structure having an improved inlet opening for engine air
Publication Date: 2026.02.18 AIRBUS DEFENCE & SPACE GMBH
  • EP4365085B1 patent drawingFigure 1~2
  • EP4365085B1 patent drawingFigure 3~4
  • EP4365085B1 patent drawingFigure 5~6

AI summary

An aircraft structure (10) having a fuselage (20), an engine (70) and an air inlet (100) for receiving air for the engine is specified. The air inlet has a cowl which surrounds an inlet opening. The air inlet furthermore has a compression surface (102) and a transition shoulder (104). The air inlet (100) additionally has a flow guide surface (110), which is arranged as a local elevation in a region of the transition shoulder (104) and extends into the inlet opening. This flow guide surface designed as a local elevation contributes to improving the displacement of the boundary layer of a fluid flowing along the aircraft structure at the air inlet.