Abradable Turbine Seal With Guide Vanes for Leakage Flow Straightening

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Solution Overview

Problem

Existing turbomachine turbines suffer from significant leakage flow due to radial clearance between blade tips and the stator, which reduces efficiency by allowing gas to bypass the blades, and this clearance cannot be completely eliminated due to differential expansions during operation.

Innovation Solution

An abradable element with integrated flow straighteners is produced via additive manufacturing, incorporating a honeycomb structure and straighteners that straighten the leakage flow to match its gyration with the main flow, reducing pressure losses and improving efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If radial clearance is reduced to minimize leakage flow, then turbine efficiency is improved, but blade tips contact the stator causing friction and wear

Engineering Contradiction:

Improveleakage flowVSAvoidfriction and wear

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

An abradable element is introduced as an intermediary between the blade tips and the stator. This element has a softer material composition than the blade tips, allowing controlled wear on the abradable element surface rather than on the expensive blade tips. The abradable element maintains the necessary radial clearance while providing a sacrificial wear surface that protects the rotor blades.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The radial clearance is optimized to a specific range (0.5-2mm) that balances leakage flow reduction with preventing blade-stator contact. The abradable element's material properties are selected to provide appropriate hardness and wear characteristics, creating a surface that can be worn down to maintain clearance while protecting the rotor.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If abradable elements with honeycomb structure are used to maintain clearance, then blade tip wear is reduced, but leakage flow increases due to radial clearance

Engineering Contradiction:

Improveblade tip durabilityVSAvoidleakage flow

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The abradable element is divided into multiple radial segments or cells forming a honeycomb structure. Each cell is a separate sealing chamber that can independently adapt to blade tip position variations. This segmentation allows the structure to maintain effective sealing across the entire circumference while accommodating thermal expansion and manufacturing tolerances.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the abradable element have different properties: the outer peripheral portion has enhanced sealing characteristics with flow straighteners, while the inner regions provide structural support. The honeycomb cells have varying dimensions and orientations optimized for local flow conditions, creating zones of different sealing effectiveness.

Inventive Principle:

Principle #3Local quality

3Loss of energy

If flow straighteners are added to the abradable element to reduce leakage flow gyration, then turbine efficiency is improved, but device complexity increases

Engineering Contradiction:

Improveleakage flow gyrationVSAvoidabradable element structure

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The flow straighteners are integrated directly into the honeycomb structure of the abradable element, merging two functions (sealing and flow control) into a single component. The flow straighteners are formed as extensions of the honeycomb cell walls, eliminating the need for separate flow control devices and reducing assembly complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The honeycomb structure itself acts as a porous medium that naturally straightens flow through its cellular geometry. The repeated hexagonal patterns create tortuous flow paths that gradually align the leakage flow with the main flow direction, reducing gyration without requiring additional active flow control mechanisms.

Inventive Principle:

Principle #31Porous materials

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 straightening of leakage flow facilitates its reintroduction into the main flow, significantly enhancing turbine efficiency by minimizing gyration and pressure losses.

Implementation Method 1

The layer of cellular material incorporates a series of flow straighteners extending from the wear face of the cellular layer, to straighten the leakage flow

Methodology Applied

Scientific EffectFlow straightening:

Data Source

PatentEP3987156B1Turbine for a turbomachine with an abradable element comprising a wear face provided with guide vanes

Publication Date: 2026.04.08 SAFRAN AIRCRAFT ENGINES SAS

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Figure 5~6

AI summary

The invention relates to an abradable element (3) for a turbine of a turbomachine, comprising a layer (12) of cellular-structure material having walls (13) defining parallel wells (14) which extend through a wear face (21) of this layer. According to the invention, this layer (12) of cellular material is obtained by additive manufacturing in order to integrate at least one guide vane (17a-17d, 19a-19d) protruding beyond its wear face (21).