Aircraft Engine Reduction Gearbox Selective Transmission Path

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Solution Overview

Problem

Turboprop gas turbine engines face performance issues and insufficient air/power generation when the power turbine shaft is blocked, particularly in hot weather, due to the propeller brake preventing rotation, which is detrimental to engine performance and air/power generation efficiency.

Innovation Solution

A reduction gearbox for aircraft engines with a selectively configurable transmission path that allows the input pinion to drive the generator drive gear independently of the output gear, enabling the engine to function as an auxiliary power unit without rotating the propeller, by engaging or disengaging specific portions of the transmission path and using a brake to prevent propeller rotation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the propeller brake is engaged to prevent rotation of the power turbine shaft, then the engine can function as an auxiliary power unit to drive the generator, but the engine performance deteriorates and air/power generation becomes insufficient

Engineering Contradiction:

Improveability to function as auxiliary power unitVSAvoidengine performance and power generation

Core Design Contradiction:

Adaptability or versatilityVSPower

Solution Approach 1:

The transmission path is divided into two separable portions: a first portion connecting the power shaft to the generator, and a second portion connecting to the propeller. By disengaging these portions, the system allows the generator to be driven independently without rotating the propeller, thus maintaining engine performance while enabling auxiliary power unit functionality.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The reduction gearbox acts as an intermediary mechanism between the power shaft and the generator/propeller system. It provides a selective engagement/disengagement interface that allows the generator to be driven by the power shaft without necessarily driving the propeller, resolving the contradiction between auxiliary power function and engine performance.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If the power turbine shaft rotation is blocked by the propeller brake, then the generator can be driven by the high pressure shaft, but the amount of air and power generated is insufficient

Engineering Contradiction:

Improveability to drive generator without propeller rotationVSAvoidamount of air generated

Core Design Contradiction:

Adaptability or versatilityVSQuantity of substance

Solution Approach 1:

The transmission system is segmented into independent drivable paths, allowing the generator to receive power from the power shaft through the disengaged first portion of the transmission path without requiring propeller rotation, thus maintaining adequate air flow and power generation.

Inventive Principle:

Principle #1Segmentation

3Reliability

If the input gear and output pinion are drivingly engaged, then the transmission path is continuous and the propeller rotates with the generator, but the engine cannot function efficiently as an auxiliary power unit

Engineering Contradiction:

Improvetransmission path continuityVSAvoidability to operate as auxiliary power unit

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The engagement state between the input gear and output pinion is made dynamic and selectable. The reduction gearbox can be configured to engage or disengage these components based on operational requirements, allowing the system to switch between continuous transmission (propeller rotation) and independent generator drive (auxiliary power unit mode).

Inventive Principle:

Principle #15Dynamics

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 allows the engine to drive the generator and accessories without rotating the propeller, improving performance and air/power generation efficiency, especially in hot weather conditions, and eliminates the need for a separate auxiliary power unit.

Implementation Method 1

an input pinion configured to be driven by the aircraft engine; an input gear meshed with the input pinion; a drive gear meshed with the input gear; an output pinion; an output gear meshed with the output pinion

Methodology Applied

Scientific EffectGear meshing: Gear

Data Source

PatentUS10400858B2Reduction gearbox for aircraft engine

Publication Date: 2019.09.03 PRATT & WHITNEY CANADA CORP

AI summary

A reduction gearbox for an aircraft engine, including an input pinion configured to be driven by the aircraft engine, a input gear meshed with the input pinion, a drive gear meshed with the input gear, an output pinion, and an output gear meshed with the output pinion and configured to drive an output shaft of the aircraft engine. The reduction gearbox is selectively configurable between an engaged configuration where the input gear and output pinion are drivingly engaged and a disengaged configuration where the input gear is rotatable independently of the output pinion. The output shaft may drive a propeller and the gearbox may include a propeller brake. A method of driving a generator of a turboprop engine is also discussed.