Thrust Reverser Blocker Door Axial Overlap Drag Reduction

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Solution Overview

Problem

Existing aircraft thrust reversers experience high drag during normal forward flight, which affects propulsion system efficiency.

Innovation Solution

The design incorporates a thrust reverser cascade, a fan ramp fairing, and a blocker door that axially translates and overlaps the fairing surface to reduce drag by optimizing airflow and minimizing inter-component gaps during different operational modes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a traditional thrust reverser configuration is used, then reverse thrust function is provided, but drag is high during normal forward flight

Engineering Contradiction:

ImprovedragVSAvoidreverse thrust function

Core Design Contradiction:

Loss of energyVSEase of operation

Solution Approach 1:

The thrust reverser system is divided into functionally independent segments: the blocker door assembly that seals the bypass airflow path, the thrust reverser cascade that redirects exhaust气流, and the fan ramp fairing that smooths airflow. This segmentation allows each component to be optimized for its specific function while collectively reducing drag during forward flight and providing effective reverse thrust when deployed

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The blocker door is positioned forward of the thrust reverser cascade in the stowed configuration, preliminarily sealing off the bypass airflow path before the aircraft needs reverse thrust. This preliminary positioning creates a streamlined fairing surface that reduces drag during normal forward flight, and the blocker door can quickly deploy to block bypass airflow when reverse thrust is activated

Inventive Principle:

Principle #10Preliminary action

2Loss of energy

If the blocker door is positioned forward of the thrust reverser cascade, then drag is reduced during forward flight, but the complexity of the mechanism increases

Engineering Contradiction:

ImprovedragVSAvoidmechanism complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The blocker door is integrated with the thrust reverser cascade structure, sharing common mounting points and actuation mechanisms. The blocker door assembly is combined with the fairing surface to create a unified aerodynamic structure that reduces drag while maintaining mechanical simplicity through shared components and streamlined actuation systems

Inventive Principle:

Principle #5Merging (Combining)

3Productivity

If the fan ramp fairing provides a forward boundary for bypass air, then airflow is optimized, but gaps between components increase drag

Engineering Contradiction:

Improveairflow efficiencyVSAvoiddrag from gaps

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The fairing surface is designed with varying local geometries: it is streamlined and smooth in regions where bypass airflow passes to reduce form drag, while providing tight seals and minimal gaps at critical interfaces between the blocker door, fan ramp fairing, and thrust reverser cascade. This local optimization of surface quality ensures efficient airflow guidance while minimizing drag-inducing gaps

Inventive Principle:

Principle #3Local quality

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 reduces drag, enhancing propulsion system performance by ensuring a smooth airflow transition and minimizing gaps between components, thereby improving thrust efficiency during both stowed and deployed positions.

Implementation Method 1

The fan ramp fairing is configured with a fairing surface that provides a forward boundary for bypass air flowing into the thrust reverser cascade

Methodology Applied

Scientific EffectAirflow optimization:

Implementation Method 2

The blocker door is configured to completely axially overlap the fairing surface during a second mode of operation

Methodology Applied

Scientific EffectDrag reduction:

Data Source

PatentUS10184426B2Thrust reverser with forward positioned blocker doors

Publication Date: 2019.01.22 ROHR INC

AI summary

An assembly is provided for an aircraft propulsion system. This assembly includes a thrust reverser cascade, a fan ramp fairing and a blocker door. The thrust reverser cascade extends along an axial centerline from a forward cascade end to an aft cascade end. The fan ramp fairing is disposed at the forward cascade end. The fan ramp fairing is configured with a fairing surface that provides a forward boundary for bypass air flowing into the thrust reverser cascade during a first mode of operation. The blocker door is configured to completely axially overlap the fairing surface during a second mode of operation.