Exoskeletal Gas Turbine Engine Design for Weight Reduction

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Solution Overview

Problem

Traditional gas turbine engines face issues with heavy and difficult-to-balance compressor and turbine disks, air leakage leading to reduced aero efficiency, and high rotating inertia that can result in engine failure, along with blade tension causing creep and thermal expansion issues.

Innovation Solution

An exoskeletal gas turbine engine design where compressor and turbine blades are attached to a rotating outer shaft enclosed in a stationary casing, with a combustor section in between, featuring a lighter outer shaft made of metal with non-metallic composite layers and vanes to guide airflow, and bearings with smaller diameters to reduce stress and improve lubrication.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If traditional compressor and turbine disks are used to attach blades, then the blades can be securely mounted, but the engine becomes heavy and difficult to balance

Engineering Contradiction:

Improveblade mounting securityVSAvoiddisk weight

Core Design Contradiction:

StrengthVSWeight of moving object

Solution Approach 1:

The traditional single disk structure is segmented into multiple smaller disks distributed around the periphery of the outer shaft. Each disk carries a subset of blades, which distributes the weight and reduces the moment of inertia while maintaining secure blade attachment capability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The disks are constructed using composite materials that provide high strength-to-weight ratio, enabling secure blade mounting with reduced disk mass and improved rotational characteristics

Inventive Principle:

Principle #40Composite materials

2Strength

If traditional metallic outer casing is used, then structural strength is provided, but heat is radiated to the surrounding area

Engineering Contradiction:

Improvecasing structural strengthVSAvoidheat radiation

Core Design Contradiction:

StrengthVSObject-generated harmful factors

Solution Approach 1:

The outer casing is constructed using composite materials that provide structural strength while having lower thermal conductivity and heat radiation characteristics compared to traditional metals, thereby containing heat within the engine

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The heat that would normally be radiated outward is converted into a beneficial resource by directing it toward the turbine inlet, improving the temperature of the gas entering the turbine and thereby increasing engine efficiency

Inventive Principle:

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

3Speed

If blade and vane arrangements are used in compressor and turbine sections, then gas flow is directed, but air leakage occurs which lowers aero efficiency

Engineering Contradiction:

Improvegas flow direction controlVSAvoidaero efficiency

Core Design Contradiction:

SpeedVSLoss of energy

Solution Approach 1:

Instead of attempting to contain the gas flow entirely within the blade and vane arrangements, the design inverts the approach by allowing controlled leakage and using dedicated leakage channels to direct the leaked flow productively toward the turbine, converting a harmful effect into a useful one

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The air leakage that occurs between blade and vane arrangements is captured and directed through leakage channels to the turbine inlet, where it serves as additional cooling flow and maintains pressure, converting the energy loss into a beneficial effect

Inventive Principle:

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

4Stability of the object's composition

If turbine disks have high rotating inertia to maintain operation, then operational stability is achieved, but containment capability during failure is reduced

Engineering Contradiction:

Improveoperational stabilityVSAvoidfailure containment capability

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The turbine section uses multiple smaller disks instead of a single large high-inertia disk, which reduces the overall moment of inertia while distributing the mass to maintain operational stability. The segmented structure also reduces the catastrophic consequences of disk failure

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The disks are made from composite materials that provide high strength-to-weight ratio, enabling the maintenance of operational stability with reduced mass and inertia, while improving failure containment capability through the inherent properties of composite materials

Inventive Principle:

Principle #40Composite materials

Data Source

PatentUS10927767B2Exoskeletal gas turbine engine

Publication Date: 2021.02.23 ROLLS ROYCE CORP

AI summary

An exoskeletal gas turbine engine having a rotatable outer shaft and an inner stationary case enclosed in a casing. The engine comprises a compressor section at an inlet end, a combustor section, and a turbine section at an outlet end. Rotating compressor blades and turbine blades are attached to, and extend radially inward from, an inner surface of the outer shaft. Stationary vanes are attached, and extend radially outward from, an outer surface of the inner stationary case. The outer shaft rotates around a front bearing and a rear bearing. An inlet compressor blade arrangement is attached to the outer race of the front bearing. An outlet turbine blade arrangement is attached to the outer race of the rear bearing. The inner race of the front and rear bearings attach to the inner stationary case.