Turbomachine Rotor Disk Elliptical Borehole Stress Reduction

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Solution Overview

Problem

Rotor disks in turbomachines experience stress peaks due to high prestressing and centrifugal forces, leading to potential damage and reduced lifetime, particularly in cylindrical and elongated boreholes.

Innovation Solution

Designing rotor disks with elliptical boreholes having a smaller outlet passage cross-sectional area than the inlet, which reduces stress peaks by monotonic reduction in passage cross-sectional area, and incorporating offset midpoints and rounded edges for improved structural mechanics and fabrication.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If cylindrical or elongated boreholes are used in rotor disks, then fluid passage function is achieved, but stress peaks occur on borehole flanks leading to damage and reduced lifetime

Engineering Contradiction:

Improvelifetime of rotor diskVSAvoidstress peaks on borehole flanks

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

The patent applies asymmetry by transitioning from symmetric cylindrical/elongated boreholes to asymmetric tapered boreholes with elliptical cross-sections. The borehole has a larger inlet opening and a smaller outlet opening, creating an asymmetric geometry that redistributes stress more evenly along the borehole flanks, thereby reducing stress peaks and improving rotor disk lifetime

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent changes geometric parameters of the borehole by varying the cross-sectional area along its length. The passage cross-sectional area is reduced monotonically from the inlet to the outlet, creating a tapered configuration that alters stress distribution patterns and reduces peak stresses on the borehole flanks

Inventive Principle:

Principle #35Parameter changes

2Stress or pressure

If passage cross-sectional area is reduced monotonically from inlet to outlet, then stress peaks are reduced, but manufacturing complexity increases

Engineering Contradiction:

Improvestress peaks on borehole flanksVSAvoidborehole fabrication complexity

Core Design Contradiction:

Stress or pressureVSEase of manufacture

Solution Approach 1:

The patent implements a monotonic reduction of passage cross-sectional area from inlet to outlet, creating a tapered borehole geometry. This parameter change achieves stress reduction while maintaining manufacturability through controlled variation of cross-sectional dimensions along the borehole length

Inventive Principle:

Principle #35Parameter changes

3Stress or pressure

If elliptical openings with offset midpoints are used, then stress distribution is improved, but manufacturing precision requirements increase

Engineering Contradiction:

Improvestress distribution on borehole flanksVSAvoidalignment precision of inlet and outlet openings

Core Design Contradiction:

Stress or pressureVSManufacturing precision

Solution Approach 1:

The patent employs asymmetric elliptical openings where the inlet and outlet openings are offset relative to each other. This asymmetric arrangement improves stress distribution by avoiding alignment of the openings, thereby preventing stress concentration at aligned edges while the offset configuration provides natural stress relief

Inventive Principle:

Principle #4Asymmetry

Data Source

PatentUS9151163B2Turbomachine rotor disk

Publication Date: 2015.10.06 MTU AERO ENGINES GMBH

AI summary

A rotor disk for a turbomachine, which is connectable to at least one rotor blade and/or a shaft of the turbomachine, having at least one borehole, which has an elliptical inlet opening having a first passage cross-sectional area and an elliptical outlet opening having a second passage cross-sectional area, so that the second passage cross-sectional area is smaller than the first passage cross-sectional area.