Twisted Exhaust Mixer Protrusions for Core-Bypass Flow Mixing

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Solution Overview

Problem

Existing turbofan engines require improved mixing solutions for high and low velocity fluid flows to enhance performance and thrust.

Innovation Solution

An exhaust mixer assembly with axially extending protrusions, twisted about a parallel axis, is used to promote mixing between core and bypass gas flows, creating streamwise vortices and reducing angular momentum, thereby enhancing mixing efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If traditional smooth exhaust mixer designs are used, then manufacturing is simpler, but mixing efficiency between core and bypass flows is insufficient

Engineering Contradiction:

Improvemixing efficiencyVSAvoidexhaust mixer structure

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The exhaust mixer trailing edge is segmented into multiple discrete protrusions distributed around the circumference, rather than using a continuous smooth surface. Each protrusion acts as an independent mixing element that generates vortices, thereby enhancing mixing efficiency while maintaining a manageable structural complexity through modular segmentation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The protrusions incorporate twisted or curved geometries about their respective protrusion axes, creating streamlined vortex structures. This curvature principle transforms the simple axial protrusions into three-dimensional twisted elements that efficiently generate rotational flow patterns, improving mixing while the regular distribution maintains structural regularity.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Productivity

If more protrusions are added to enhance mixing, then mixing performance improves, but manufacturing complexity increases

Engineering Contradiction:

Improvemixing performanceVSAvoidexhaust mixer fabrication

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The protrusions are distributed at specific circumferential locations around the exhaust mixer trailing edge, concentrating mixing enhancement at key positions rather than requiring continuous complexity. This local placement strategy achieves effective mixing performance while leaving other regions simpler, thereby balancing manufacturing ease with mixing performance.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

A plurality of protrusions are provided around the circumference, which may be fewer than a continuous surface would require, yet sufficient to generate adequate mixing through vortex formation. This partial action approach provides effective mixing enhancement without the excessive complexity of a fully continuous structured surface.

Inventive Principle:

Principle #16Partial or excessive action

3Productivity

If twisted protrusions are used, then vortex generation and mixing are enhanced, but manufacturing precision requirements increase

Engineering Contradiction:

Improvevortex generation efficiencyVSAvoidprotrusion twist geometry

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The protrusions are designed with twisted geometries that follow smooth curved paths about their protrusion axes. These regular curved patterns, while more complex than straight lines, maintain geometric consistency that can be achieved through standard forming processes, balancing vortex generation efficiency with manufacturability.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The twist angle and curvature parameters of the protrusions are optimized to achieve effective vortex generation within manufacturable limits. By carefully selecting geometric parameters such as twist angle, protrusion height, and distribution spacing, the design achieves high mixing efficiency while remaining compatible with conventional manufacturing precision capabilities.

Inventive Principle:

Principle #35Parameter changes

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 twisted protrusions improve engine acoustics and specific fuel consumption by strengthening mixing and reducing frictional dissipation, leading to increased thrust and performance.

Implementation Method 1

at least one of the plurality of protrusions being twisted about a protrusion axis extending through the at least one of the plurality of protrusions, the protrusion axis parallel to the central axis

Methodology Applied

Scientific EffectVortex: Vortex Ring

Data Source

PatentUS12442532B2Exhaust mixer with protrusions

Publication Date: 2025.10.14 PRATT & WHITNEY CANADA CORP

AI summary

An exhaust mixer assembly for a gas turbine engine includes a core passage extending along a central engine axis for directing a core gas flow. An outer annular passage coaxially surrounds the core passage for directing a bypass gas flow. An exhaust mixer communicating with the core passage and the outer annular passage has an upstream end, a downstream end and an annular wall extending therebetween. A plurality of protrusions extend axially from a downstream end of the annular wall to form a jagged trailing edge of the exhaust mixer. Each of the plurality of protrusions extend separately from the downstream end of the annular wall from the other of the plurality of protrusions. At least one of the plurality of protrusions is twisted about a protrusion axis extending through the at least one of the plurality of protrusions, the protrusion axis parallel to the central axis.