Zero Clearance Centrifugal Compressor Rotor Shift

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Solution Overview

Problem

Centrifugal compressors in gas turbine engines face challenges due to relative motion and thermal expansion mismatches between static and rotating structures, leading to increased clearances that affect efficiency and stability, especially during transient operations like hot re-burst conditions.

Innovation Solution

A zero running clearance system is implemented using a rotor shift device and thrust bearing, which adjusts the rotor's position relative to the static wall to maintain minimal clearance through axial movement, utilizing a tower shaft engagement device and optional sensors to optimize compressor efficiency and prevent rubs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the static wall contour and rotating blade contour are configured to coincide at the most severe transient condition, then the minimum clearance is maintained during transient operation, but the clearance increases during steady state operation reducing efficiency

Engineering Contradiction:

Improveclearance maintenance during transient operationVSAvoidcompressor efficiency during steady state

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The rotor is made dynamically adjustable through a rotor shifting mechanism that allows the rotor position to be changed between transient and steady state operating conditions. During transient conditions, the rotor is positioned to maintain minimum clearance for reliability, while during steady state, the rotor is repositioned to optimize efficiency, thus resolving the contradiction between reliability and productivity

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the positional parameter of the rotor relative to the static wall based on operating conditions. By adjusting the rotor position parameter dynamically, the system optimizes clearance characteristics for different operating modes, maintaining reliability during transients while improving productivity during steady state operation

Inventive Principle:

Principle #35Parameter changes

2Strength

If thermal expansion mismatch between rotor and static wall is accommodated, then structural integrity is maintained during hot re-burst, but running clearance increases reducing compressor performance

Engineering Contradiction:

Improvestructural integrity during thermal transientVSAvoidcompressor performance

Core Design Contradiction:

StrengthVSProductivity

Solution Approach 1:

The rotor shifting mechanism dynamically adjusts rotor position to compensate for thermal expansion effects. During hot re-burst transients, the rotor position is adjusted to maintain structural integrity by accommodating thermal mismatch, while during normal operation, the rotor is repositioned to minimize running clearance and optimize compressor performance

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system performs preliminary positioning adjustments during transient events to prevent excessive clearance development. By proactively shifting the rotor position during hot re-burst conditions, the system maintains structural integrity and prevents the thermal expansion mismatch from causing performance-degrading clearances

Inventive Principle:

Principle #10Preliminary action

3Stability of the object's composition

If relative motion between static and rotating structures is compensated, then clearance stability is improved, but device complexity increases due to additional control mechanisms

Engineering Contradiction:

Improveclearance stabilityVSAvoidcontrol mechanism complexity

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

A dynamic rotor shifting mechanism is introduced that actively compensates for relative motion between static and rotating structures. This mechanical dynamic adjustment system improves clearance stability by continuously adapting rotor position to accommodate thermal and pressure-induced movements, accepting increased device complexity as the cost of achieving stable clearance characteristics

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 maintains minimal clearance between rotor and static structures during steady and transient states, enhancing compressor efficiency and stability by compensating for structural mismatches and thermal expansions, thereby optimizing engine performance.

Implementation Method 1

a thrust bearing disposed in connection with the rotor

Methodology Applied

Scientific EffectThrust bearing: Ball Bearing

Implementation Method 2

the deflections of the structures caused by pressure, radial and axial thermal expansion

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 3

the deflections of the structures caused by pressure

Methodology Applied

Scientific EffectPressure deflection: Deformation

Data Source

PatentUS7824151B2Zero running clearance centrifugal compressor

Publication Date: 2010.11.02 RTX CORP

AI summary

A turbine engine includes an engine housing enclosing: a centrifugal compressor having a rotor; at least one centrifugal compressor bore mounted to the rotor; at least one blade mounted to each of the at least one centrifugal bore and disposed proximate to at least one static wall; a turbine disposed in connection with the centrifugal compressor; a thrust bearing disposed in connection with the rotor; and means for moving said rotor with reference to the at least one static wall attached to the thrust bearing.