Gas Turbine Starter Generator Low Spool Segmentation

Solution Overview

Problem

Gas turbine engine start systems face challenges in maintaining compressor stability due to horsepower extraction from the high spool, which affects engine performance and design constraints within the available space.

Innovation Solution

The starter/generator is positioned forward or aft of the low spool, driven by the low spool through a towershaft, and a flow control mechanism redirects fan airflow to the core flow path to reduce the workload on the high spool during startup, eliminating the need for a gearbox on the high spool and allowing for counter-rotation of the spools.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If horsepower is extracted from the high spool to drive accessories and generator, then the engine can operate accessories during flight, but compressor stability is degraded

Engineering Contradiction:

Core Design Contradiction:

Ease of operationVSStability of the object's composition

Solution Approach 1:

The power transmission system is segmented into two independent spools: a high spool for compressor-driven accessories and a low spool for fan-driven accessories. This segmentation allows the high spool to maintain compressor stability while the low spool provides sufficient power for accessories during flight without extracting horsepower from the high spool.

Inventive Principle:

Principle #1Segmentation

2Power

If a high spool starter/generator and gearbox are installed to drive accessories, then power transmission is enabled, but engine weight and complexity increase

Engineering Contradiction:

Core Design Contradiction:

PowerVSDevice complexity

Solution Approach 1:

The gearbox and high spool starter/generator are extracted from the high spool system and relocated to the low spool system. The low spool starter/generator drives the low spool through a towershaft, eliminating the need for a high spool gearbox and reducing overall engine complexity while maintaining power transmission capability.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The mechanical gearbox system on the high spool is replaced with an electrically-driven low spool starter/generator system. This substitution reduces mechanical complexity by eliminating the high spool gearbox while providing equivalent or superior power transmission capability through electrical motor control.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Use of energy by moving object

If accessories are driven from the high spool gearbox, then power is available during operation, but high compressor stability is debited

Engineering Contradiction:

Core Design Contradiction:

Use of energy by moving objectVSStability of the object's composition

Solution Approach 1:

Accessory power requirements are segmented between two independent spools: the high spool maintains compressor stability while the low spool provides accessory power during flight. This segmentation eliminates the need to extract horsepower from the high spool, thereby preserving compressor stability while meeting accessory power demands.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentEP2617980B1Gas turbine engines

Publication Date: 2021.03.31

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AI summary

A gas turbine engine (20) includes a flow control mechanism (60) operable to direct at least a portion of a fan airflow from a secondary flow path (56) into a core flow path (58).