Flight Deck Mix Muff Layout for Branch Duct Icing Prevention

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Solution Overview

Problem

Aircraft air conditioning systems face icing issues in branch air ducts, which diminish airflow to the flight deck, as conventional trim air injection methods do not prevent icing upstream of the injection point and in the theoretical takeoff area.

Innovation Solution

A ventilation air mixer, referred to as a 'mix muff,' is designed with a branch air duct and a trim air mixer that surrounds the duct, allowing trim air to be injected at an acute angle and through holes in the mixing portion, warming the leading edge of the duct to reduce icing susceptibility.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If trim air is injected into the branch air duct at a conventional location, then the air temperature downstream of the injection point is improved, but icing accumulates upstream of the injection point and at the theoretical takeoff, obstructing airflow

Engineering Contradiction:

Improveair temperature downstream of trim air injectionVSAvoidicing accumulation upstream of injection point

Core Design Contradiction:

TemperatureVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by directing trim air forward toward the theoretical takeoff and inlet area before the main airflow reaches those points. The acute angle orientation of the trim air source duct connection causes warm trim air to be injected upstream, preemptively warming critical areas before ice can form, rather than merely responding to cold conditions downstream after injection.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent segments the trim air injection function into multiple zones by using an acute angle orientation that distributes warm air both upstream toward the theoretical takeoff and downstream into the main duct. This creates separate warming zones: one preventing ice at the theoretical takeoff/inlet area, and another maintaining temperature downstream, thereby addressing icing problems at multiple locations simultaneously.

Inventive Principle:

Principle #1Segmentation

2Temperature

If conventional trim air injection methods are used, then air temperature control is achieved at the injection point, but airflow is obstructed by ice buildup in critical areas

Engineering Contradiction:

Improveair temperature at injection pointVSAvoidairflow to flight deck

Core Design Contradiction:

TemperatureVSProductivity

Solution Approach 1:

The patent prevents airflow obstruction by performing preliminary warming action at the theoretical takeoff and inlet areas where ice most commonly forms. By orienting the trim air source duct connection at an acute angle, warm air is delivered before the cold conditioned air reaches vulnerable zones, preemptively eliminating conditions that would lead to ice accumulation and subsequent airflow blockage.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent converts the potentially harmful cold conditioned air that causes icing into a beneficial flow pattern. The acute angle orientation of the trim air injection creates a flow configuration where warm trim air rides along and warms the cold conditioned air stream, transforming the cold air from a hazard into a controlled flow that maintains temperature and prevents ice formation while still delivering conditioned air to the flight deck.

Inventive Principle:

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

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 effectively reduces icing at the takeoff and stagnation areas, maintaining consistent airflow to the flight deck by warming the duct surfaces above freezing.

Implementation Method 1

directing warm trim air at an acute angle to the inlet of the branch air duct, reducing icing by warming the leading edge and low-velocity areas

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

cold air leaving the air conditioning pack then travels via a pack source duct to a mixing chamber, referred to as a 'mix manifold', where the cold air is mixed with filtered recirculated air from the aircraft's cabin

Methodology Applied

Scientific EffectConvection: Convection

Data Source

PatentUS10023317B2Flight deck takeoff duct and trim air mix muff

Publication Date: 2018.07.17 THE BOEING CO

AI summary

An exemplary ventilation air mixer includes a branch air duct and a trim air mixer. The branch air duct has an inlet that is configured to be coupled to a takeoff port of a main air source duct. The branch air duct has multiple holes arranged about a wall of a mixing portion. The trim air mixer at least partially surrounds the branch air duct and forms a cavity extending from the inlet of the branch air duct to at least the mixing portion. The trim air mixer has a trim air source duct connection coupled at an angle about a midsection. The angle is substantially acute relate to a longitudinal axis of the branch air duct such that trim air entering into the trim air mixer via the trim air source duct connection is directed toward the inlet of the branch air duct.