Compressor Casing Temperature Gradient Control via Dual Modulation Valves

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Solution Overview

Problem

Temperature gradients across the outer compressor casing in gas turbine engines can cause 'bowing' or centerline shifts, leading to blade tip rubs, hardware damage, efficiency losses, and startup delays due to buoyant plume effects during startup, especially in double wall compressors with no dedicated airflow.

Innovation Solution

A temperature gradient control system that includes upper and lower discharge piping with modulation valves and thermocouples to modulate airflow through the cavity between the inner and outer casings, reducing temperature gradients by extracting air from the top and bottom and adjusting flow based on measured temperatures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If no dedicated airflow is provided through the cavity in a double wall compressor casing, then the structure is simpler, but temperature gradients develop during startup causing casing bowing and blade tip rubs

Engineering Contradiction:

Improvecasing structure complexityVSAvoidblade clearance stability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent extracts hot air from the cavity between the inner and outer casings through strategically positioned extraction ports. By removing the problematic hot air that causes temperature gradients and casing bowing, the system maintains blade clearance stability without requiring a completely different casing structure

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces an intermediary airflow system that passes cooling air through the cavity to counteract the buoyant plume effects. This intermediary flow acts as a mediator between the hot combustion gases and the outer casing, preventing excessive temperature gradients while maintaining structural simplicity

Inventive Principle:

Principle #24Intermediary (Mediator)

2Use of energy by moving object

If the cavity experiences buoyant plume effects during startup, then natural convection occurs, but temperature differentials drive metal temperature gradients causing casing centerline shifts

Engineering Contradiction:

Improvenatural convection utilizationVSAvoidcasing temperature gradient

Core Design Contradiction:

Use of energy by moving objectVSTemperature

Solution Approach 1:

The patent implements a feedback control system where temperature sensors monitor the cavity temperature distribution, and this information feeds back to a controller that adjusts extraction valve positions. This closed-loop feedback actively compensates for temperature gradients caused by buoyant plume effects, maintaining uniform casing temperature

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent transitions from a static casing structure to a dynamic control system where extraction ports and valves can be actively adjusted during operation. The system dynamically responds to changing temperature conditions during startup and operation, optimizing airflow to prevent temperature gradients while utilizing natural convection when beneficial

Inventive Principle:

Principle #15Dynamics

3Strength

If the outer casing temperature gradient causes bowing or centerline shift, then structural integrity is maintained, but blade tip clearances increase leading to efficiency losses and potential rubs

Engineering Contradiction:

Improvecasing structural integrityVSAvoidengine efficiency

Core Design Contradiction:

StrengthVSProductivity

Solution Approach 1:

The patent applies preliminary cooling action during startup before the casing reaches critical temperatures. By introducing cooling airflow through the cavity early in the startup sequence, the system prevents temperature gradients from developing to levels that would cause excessive bowing and clearance increases, thereby maintaining engine efficiency from the outset

Inventive Principle:

Principle #10Preliminary action

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 system effectively reduces temperature gradients across the outer casing, preventing structural shifts and improving engine efficiency, startup speed, and overall performance by maintaining tighter blade clearances.

Implementation Method 1

a flow of air is pulled through the cavity... modulate the flow of air pulled through the cavity of the double wall casing to reduce a temperature gradient across the outer casing

Methodology Applied

Scientific EffectConvection: Convection

Implementation Method 2

An upper thermocouple and a lower thermocouple may be positioned on the outer casing... reduce a temperature gradient across the outer casing as determined by the upper thermocouple and lower thermocouple

Methodology Applied

Scientific EffectThermocouple: Thermocouple

Data Source

PatentUS11668206B1Temperature gradient control system for a compressor casing

Publication Date: 2023.06.06 GE INFRASTRUCTURE TECH LLC

AI summary

This application provides a temperature gradient control system for a double wall casing of a compressor. The double wall casing may include an inner casing and an outer casing such that a flow of air is pulled through the double wall casing. The temperature gradient control system may include upper discharge piping with an upper modulation valve and a lower discharge piping with a lower modulation valve. The upper modulation valve and/or the lower modulation valve modulate the flow air pulled through the double wall casing to reduce a temperature gradient across the outer casing.