Bleed System Mixer Duct Geometry for Low-Loss Thermal Gradient Control

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Solution Overview

Problem

Aircraft ducts face challenges in managing high temperature gradients from bleed air, leading to material degradation and increased pressure loss, especially during engine start operations, with existing solutions either being costly, heavy, or inefficient in mixing airflow.

Innovation Solution

A duct design featuring continuous pieces on the internal wall with varying tilting degrees along the longitudinal axis, deflecting cold airflow towards the warmest zone to create a vortex, reducing temperature gradients near the inner wall and minimizing pressure loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If high-temperature resistant materials (such as Inconel) are used in duct parts directly downstream of the thermal exchanger, then the duct can withstand high temperature gradients, but the material cost and weight increase significantly

Engineering Contradiction:

Improvetemperature resistanceVSAvoidduct weight

Core Design Contradiction:

TemperatureVSWeight of stationary object

Solution Approach 1:

The patent applies different material properties to different locations within the duct. Titanium material is used in regions where temperature is below 530K, while Inconel material is used only in the specific zone where temperature exceeds 530K. This localized material selection allows the duct to withstand high temperature gradients while minimizing overall weight and cost compared to using Inconel throughout the entire duct.

Inventive Principle:

Principle #3Local quality

2Temperature

If mixing devices (such as propeller-shaped devices) are installed in the duct to rapidly mix airflow, then maximum temperature decreases as air flows through, but pressure loss increases significantly

Engineering Contradiction:

Improvetemperature mixingVSAvoidpressure loss

Core Design Contradiction:

TemperatureVSLoss of energy

Solution Approach 1:

The patent extracts the mixing function from separate mechanical mixing devices and integrates it into the duct wall structure itself. The凹部 (recesses) are formed directly in the duct wall, creating a streamlined geometry that promotes natural airflow mixing without requiring additional propeller-shaped mixing devices. This eliminates the pressure loss associated with mechanical mixing devices while still achieving temperature uniformity.

Inventive Principle:

Principle #2Taking out (Extraction)

3Temperature

If static mixing devices with airfoils are arranged in the warmest sector of the airflow, then hot air is directed towards the cold sector, but manufacturing constraints prevent efficient airfoil creation within duct cross-section

Engineering Contradiction:

Improvetemperature distributionVSAvoidmanufacturing feasibility

Core Design Contradiction:

TemperatureVSEase of manufacture

Solution Approach 1:

The patent segments the duct wall into multiple regions, each with different geometric characteristics. The凹部 (recesses) are strategically positioned and sized to create specific flow patterns in different sectors of the duct. This segmentation allows the duct to redirect hot air towards cold sectors through geometric design rather than complex airfoil structures, making the design manufacturable within standard duct cross-sections.

Inventive Principle:

Principle #1Segmentation

4Loss of energy

If the duct is designed to withstand high temperature gradients without mixing devices, then pressure loss is reduced, but temperature sensors must be placed at greater distances

Engineering Contradiction:

Improvepressure lossVSAvoidduct length

Core Design Contradiction:

Loss of energyVSLength of stationary object

Solution Approach 1:

The patent incorporates mixing action directly into the duct wall geometry through the凹部 (recesses) design. As airflow passes over these recesses, mixing is initiated immediately and progressively along the duct length, rather than requiring a separate mixing section downstream. This preliminary mixing action achieves temperature uniformity faster, allowing temperature sensors to be placed at shorter distances while maintaining low pressure loss.

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

The design effectively reduces temperature gradients at the duct surface, protects materials from high temperatures, and maintains low pressure loss, allowing for shorter temperature sensor placement and reduced duct length, while being economically viable and simple to manufacture.

Implementation Method 1

deflecting cold airflow towards the warmest zone to create a vortex

Methodology Applied

Scientific EffectVortex: Vortex Ring

Implementation Method 2

deflecting cold airflow towards the warmest zone to create a vortex, reducing temperature gradients near the inner wall

Methodology Applied

Scientific EffectConvection: Convection

Data Source

PatentEP3719280B1Flow mixer duct for a bleed system

Publication Date: 2023.03.01 AIRBUS OPERATIONS SL

Figure 1(a)~2
Figure 3A~3B
Figure 4~5

AI summary

The invention provides a duct for a bleed system of an aircraft, wherein the duct extends from an inlet section to an outlet section along a longitudinal axis, and wherein it comprises a continuous piece arranged on and protruding from the internal wall of the duct. The duct is of application in duct subject to temperature gradients in order to reduce the temperature of the warmest airflow closer to the inner wall rather than rapidly mixture the airflow.