Gas Turbine Inner Casing Axial Preload for Tip Clearance Control

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing gas turbine engines face challenges in maintaining optimal radial clearance between rotating and non-rotating components due to thermal growth differences, leading to inefficiencies and potential damage, with existing active control systems being costly and complex.

Innovation Solution

A passive control system using a connection assembly with a biasing means, such as a compression spring, to axially preload an inner casing within the compressor or turbine section, allowing it to move based on pressure differentials, thereby adjusting gap clearance and maintaining efficient operation across varying engine conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If active control systems are used to maintain blade tip clearance, then clearance control precision is improved, but device complexity and cost increase

Engineering Contradiction:

Improveblade tip clearance control precisionVSAvoidcontrol system complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The system uses self-service by allowing the inner casing to automatically adjust its axial position in response to pressure differentials that naturally occur during engine operation. The biasing means provides a restoring force that works passively with these pressure changes, eliminating the need for external control systems, sensors, and actuators while maintaining effective clearance control.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The invention replaces complex mechanical control systems (feedback loops, sensors, actuators) with a simple passive mechanical mechanism consisting of a biasing means (spring) that directly couples to the inner casing. This mechanical substitution eliminates the need for electronic control systems while achieving the same functional outcome of maintaining optimal blade tip clearance.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Device complexity

If passive control systems are used, then device complexity is reduced, but control effectiveness may be insufficient

Engineering Contradiction:

Improvecontrol system complexityVSAvoidclearance control precision

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The system utilizes pneumatic principles by harnessing pressure differentials in the working fluid that naturally occur during engine operation. These pressure differentials act on the inner casing to move it axially, while the biasing means provides a restoring force. This passive pneumatic-mechanical coupling achieves effective clearance control without complex systems.

Inventive Principle:

Principle #29Pneumatics and hydraulics

3Stability of the object's composition

If the inner casing is rigidly fixed, then structural stability is improved, but adaptability to operating conditions deteriorates

Engineering Contradiction:

Improvecasing structural stabilityVSAvoidclearance adaptation to operating conditions

Core Design Contradiction:

Stability of the object's compositionVSAdaptability or versatility

Solution Approach 1:

The invention applies dynamics by making the inner casing axially movable rather than rigidly fixed. The connection assembly with biasing means allows the casing to dynamically adjust its axial position in response to changing operating conditions (pressure differentials), while maintaining structural stability through the constrained guided movement and restoring force of the biasing means.

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 solution effectively maintains a narrow tip-shroud clearance, improving engine performance and reducing fuel consumption by utilizing passive controls that react to pressure differentials, thus enhancing robustness and reducing costs compared to active systems.

Implementation Method 1

a connection assembly that slidably connects the inner casing to the outer casing for axial movement and includes a biasing means for axially preloading the inner casing in the converging direction

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

passively controlling the axial position of an inner casing within the compressor or turbine section of a gas turbine engine based on flowpath pressures

Methodology Applied

Scientific EffectPressure differential: Pressure Gradient

Data Source

PatentUS9435218B2Systems relating to axial positioning turbine casings and blade tip clearance in gas turbine engines

Publication Date: 2016.09.06 GE INFRASTRUCTURE TECH LLC

AI summary

A gas turbine engine that includes: a flowpath defined through one of a compressor and a turbine; an inner casing defining an axially tilted outboard boundary of the flowpath, which, relative to the axial tilt, defines a converging direction in which the flowpath converges and a diverging direction in which the flowpath diverges; a row of rotor blades having outer tips that oppose the outboard boundary across a gap clearance defined therebetween; an outer casing concentrically arranged about the inner casing so to form an annulus therebetween; and a connection assembly that slidably connects the inner casing to the outer casing and includes a biasing means for axially preloading the inner casing in the converging direction.