Contra-rotating Propeller Turbine Engine Axial Length Reduction

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Solution Overview

Problem

Conventional turbine engines with contrarotating propellers face issues of increased axial length, weight, and sound emissions due to the need for minimum axial spacing and complex power turbine configurations, leading to inefficiencies and higher costs.

Innovation Solution

A turbine engine design where the power turbine is mounted between the upstream and downstream propellers, connected via a step-down gearbox with an outer rotor constrained to the upstream propeller and an inner rotor driving the gearbox, allowing for reduced axial size, improved mechanical strength, and slower propeller speeds to minimize sound nuisance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If the power turbine is mounted downstream from the propellers with a step-down gearbox, then the power turbine can operate at high speed with good efficiency, but the axial length of the turbine engine increases and the propellers must be cantilevered out

Engineering Contradiction:

Improvepower turbine efficiencyVSAvoidaxial length of turbine engine

Core Design Contradiction:

PowerVSLength of moving object

Solution Approach 1:

The patent inverts the conventional arrangement by mounting the power turbine between the propellers rather than downstream, with the rotor rotating in the opposite direction to the propellers. This allows the turbine to operate at high speed for efficiency while the propellers rotate slower to reduce noise, eliminating the need for a step-down gearbox and reducing axial length.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The power turbine rotor is nested between the upstream and downstream propellers along the same axis, with the rotor occupying the space between them. This nested arrangement allows the turbine to be integrated into the existing propeller spacing, reducing the overall axial length of the engine while maintaining high-speed operation.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Object-affected harmful factors

If the propellers are mounted far apart to limit sound emissions, then noise is reduced, but the axial length increases and structural reinforcement is needed

Engineering Contradiction:

Improvesound emissionVSAvoidaxial length of turbine engine

Core Design Contradiction:

Object-affected harmful factorsVSLength of moving object

Solution Approach 1:

The patent reverses the rotation direction of the power turbine rotor relative to the propellers, allowing the turbine to operate at high speed while the propellers rotate slower. This speed differentiation enables noise reduction without increasing axial spacing between propellers.

Inventive Principle:

Principle #13The other way round (Inversion)

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 results in a compact, efficient turbine engine with reduced weight and sound emissions, achieving high efficiency with fewer blade stages and simplified fabrication, while combining the advantages of previous designs while avoiding their drawbacks.

Implementation Method 1

a power turbine (50) connected via a step-down gearbox (52) to rotors (12, 14) of the propellers

Methodology Applied

Scientific EffectThermal energy conversion: Heat Engine

Implementation Method 2

connected via a step-down gearbox (52) to rotors (12, 14) of the propellers

Methodology Applied

Scientific EffectMechanical energy transmission: Gear

Data Source

PatentUS9017028B2Turbine engine with contra-rotating non-ducted propellers

Publication Date: 2015.04.28 SAFRAN AIRCRAFT ENGINES SAS

AI summary

A turbine engine including two contrarotating unducted propellers of an upstream propeller and a downstream propeller, with a power turbine mounted axially between the two propellers, the turbine including an outer rotor constrained to rotate with the upstream propeller and an inner rotor driving rotation of an inlet shaft of a step-down gearbox, the gearbox includes an outlet shaft driving rotation of the rotor of the upstream propeller and an outlet shaft driving rotation of the downstream propeller.