Adjustable Turbine Case Tie Rods for Bearing Centerline Offset

Solution Overview

Problem

Existing methods for adjusting the center line of a bearing mount relative to a turbine casing are non-adjustable and require lengthy manufacturing coordination, making it difficult to optimize blade tip clearances and account for structural changes due to weight, deflection, and case distortion in gas turbine engines.

Innovation Solution

The use of adjustable tie rods with threaded nuts allows for the offsetting of the center line of the inner and outer turbine cases, enabling precise adjustment of the bearing's location by varying the length of the tie rods, which are circumferentially spaced and connected between the inner and outer cases.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the bearing is offset by machining the inner case bearing flanges to be nonconcentric with the outer case flanges, then the blade tip clearance can be optimized, but the manufacturing lead time increases and the adjustment is non-adjustable once machined

Engineering Contradiction:

Improveblade tip clearance optimizationVSAvoidmanufacturing lead time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The patent applies the dynamics principle by replacing the static, fixed offset achieved through machining with a dynamic, adjustable offset mechanism. The inner case is mounted to the outer case via multiple adjustable feet that can be independently positioned and secured. This allows the bearing center line offset to be adjusted during assembly and re-adjusted later if needed, transforming a permanent machining operation into a flexible mechanical adjustment system that reduces manufacturing lead time while maintaining precise clearance optimization.

Inventive Principle:

Principle #15Dynamics

2Manufacturing precision

If the bearing is offset by machining the inner case bearing flanges to be nonconcentric with the outer case flanges, then the blade tip clearance can be optimized, but the adjustment cannot be changed once machined

Engineering Contradiction:

Improveblade tip clearance optimizationVSAvoidadjustability of bearing position

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The patent applies the dynamics principle by replacing the static, fixed offset achieved through machining with a dynamic, adjustable offset mechanism. The inner case is mounted to the outer case via multiple adjustable feet that can be independently positioned and secured. This allows the bearing center line offset to be adjusted during assembly and re-adjusted later if needed, transforming a permanent machining operation into a flexible mechanical adjustment system that reduces manufacturing lead time while maintaining precise clearance optimization.

Inventive Principle:

Principle #15Dynamics

3Manufacturing precision

If the tie rods extend for distinct lengths between the inner and outer cases, then the center lines of the inner and outer cases can be offset, but the device complexity increases

Engineering Contradiction:

Improvecenter line offset precisionVSAvoidtie rod adjustment mechanism

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent applies the segmentation principle by dividing the mounting connection into multiple independent adjustable feet (typically three or more) distributed around the inner case perimeter. Each foot is a separate component with its own adjustment mechanism, allowing independent positioning. This segmentation enables precise control of the inner case offset relative to the outer case by adjusting individual feet, while the modular nature of the segmented approach actually simplifies the overall system compared to complex monolithic adjustment mechanisms.

Inventive Principle:

Principle #1Segmentation

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 provides a flexible and efficient method to adjust the bearing's center line, improving blade tip clearances and seal alignments, allowing for better engine balance and easy re-adjustment as the engine structure changes over time.

Implementation Method 1

A plurality of tie rods includes a threaded nut received on a tie rod... The nut is tightened on the tie rod to adjust the length of the tie rod and the distance between the inner and outer cases

Methodology Applied

Scientific EffectThreaded fastening: Screw

Data Source

PatentUS10982565B2Turbine case adjustment using Adjustable tie rods

Publication Date: 2021.04.20 RTX CORP

AI summary

A turbine housing section includes a radially inner case centered on a first axis, and a radially outer case spaced radially outwardly of the inner case, and centered on a second axis. The first and second axes are offset relative to each other. A plurality of tie rods include a threaded nut received on a tie rod, with the plurality of tie rods connecting the inner and outer cases. The plurality of tie rods are spaced circumferentially about both of the first and second axes, and extend for distinct lengths between the inner and outer cases such that the inner and outer cases are held at a position wherein the first and second axes are offset.