Load-Isolating Impeller Shroud Bracket for Gas Turbine

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Solution Overview

Problem

In gas turbine engines, maintaining a consistent and tight tip clearance between the impeller blades and shroud is challenging due to thermal and external loads, which can cause deflections and distortions, affecting engine performance.

Innovation Solution

A thin and curved load-isolating support bracket is integrated into the impeller shroud to secure it to the engine case, attenuating thermal and external loads and minimizing deflections, thereby maintaining a consistent tip clearance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the impeller shroud is rigidly secured to the engine case to minimize tip clearance, then pressurization efficiency is improved, but thermal and external loads cause deflections that can lead to blade-shroud contact

Engineering Contradiction:

Improvepressurization efficiencyVSAvoidblade-shroud contact risk

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

A support bracket is introduced as an intermediary component between the impeller shroud and the engine case. This bracket absorbs and isolates thermal and external loads, preventing them from being transmitted to the shroud. The bracket acts as a mediator that allows the shroud to maintain its position for optimal tip clearance while protecting it from harmful loads that could cause deflections and blade contact.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The support bracket provides beforehand cushioning by being pre-installed and pre-positioned to absorb thermal expansion and external loads before they can affect the impeller shroud. The bracket is designed to accommodate expected deflections and distortions, cushioning the shroud against these harmful effects and maintaining stable tip clearance throughout operation.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Productivity

If the tip clearance is made tight to optimize pressurization, then engine performance is improved, but the risk of blade-shroud contact under extreme thermal loads increases

Engineering Contradiction:

Improveengine performanceVSAvoidthermal load sensitivity

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The support bracket serves as a protective intermediary that shields the impeller shroud from thermal loads. By positioning the bracket between the heat source (combustion chamber) and the shroud, it mediates the thermal environment, allowing the shroud to maintain tight tip clearance for optimal performance while the bracket absorbs the harmful thermal effects.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The support bracket converts the harmful effect of thermal loads into a beneficial outcome. Instead of allowing thermal expansion to directly affect the shroud and cause blade contact, the bracket absorbs this thermal energy and distortion, converting what would be a harmful deflection into a controlled, isolated effect that actually protects the blade-shroud clearance.

Inventive Principle:

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

3Strength

If a robust support structure is used to secure the impeller shroud, then structural stability is improved, but thermal loads are transmitted to the shroud causing deflections

Engineering Contradiction:

Improvestructural stabilityVSAvoidtip clearance consistency

Core Design Contradiction:

StrengthVSStability of the object's composition

Solution Approach 1:

The support bracket is designed as a load-isolating intermediary that has sufficient structural strength to secure the impeller shroud stably, yet is configured to absorb and isolate thermal loads. The bracket's geometry and material properties are optimized to provide structural stability while acting as a thermal barrier, preventing heat transmission to the shroud that would cause deflections and clearance variations.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

The load-isolating support bracket effectively reduces the impact of external loads on the impeller shroud, ensuring a tight and consistent tip clearance, enhancing the engine's pressurization efficiency and overall performance.

Implementation Method 1

Due to thermal and other external loads, the impeller shroud may deflect

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

the deflections and distortions of the impeller blades due to thermal effects and centrifugal loading is most pronounced at the tips of the blades

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Data Source

PatentUS7908869B2Thermal and external load isolating impeller shroud

Publication Date: 2011.03.22 PRATT & WHITNEY CANADA CORP

AI summary

A gas turbine engine has a compressor assembly and a turbine assembly rotationally mounted on a shaft, the turbine assembly being driven by hot gases discharged from a combustion chamber disposed between the compressor and turbine assemblies, the compressor having a centrifugal impeller for pressurizing and impelling air into the combustion chamber. The engine also includes an impeller shroud covering the bladed portion of the centrifugal impeller, the impeller shroud having a support bracket having a thin and curved load-isolating profile for supporting a strut that secures the impeller shroud to a case of the engine.