Gas Turbine Vane Tip Retention Using Flexible Grommet Design
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Solution Overview
Problem
Gas turbine engine vane assemblies downstream of the engine fan or low pressure compressor face issues with foreign object damage, where sharp vane edges can cut grommets and cause damage to surrounding components, and the airflow can displace grommets, necessitating adhesives for retention, which complicates installation and affects engine performance.
Innovation Solution
A vane assembly design featuring a blunt button portion on the vane tip and a flexible grommet with tongues and a slit, which eliminates the need for adhesives by using airflow to maintain grommet position and reduces the risk of damage from foreign object impacts, with the grommet and shroud configuration ensuring smooth airflow and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a grommet is inserted in the slot to surround the vane tip, then the vane tip is retained in the shroud, but the grommet can be cut by sharp vane edges during foreign object damage events and displaced by airflow
Solution Approach 1:
The grommet is divided into multiple segments or lobes that can independently deform and flex. This segmentation allows the grommet to absorb impact forces from foreign objects without failing, and to withstand airflow forces without displacing, while still effectively retaining the vane tip.
Solution Approach 2:
The grommet material properties are modified to achieve optimal balance between retention strength and damage resistance. The material is selected or engineered to have specific elasticity, hardness, and tensile strength parameters that allow it to withstand both sharp edge contact and airflow forces.
2Reliability
If adhesive is used to ensure grommet stays in place, then the grommet is secured against displacement, but the installation and replacement of vanes becomes complicated
Solution Approach 1:
The grommet is designed to self-retain the vane tip through its elastic deformation and geometric configuration. The grommet's structure allows it to automatically grip and hold the vane tip without requiring external adhesives or additional fastening mechanisms, enabling simple installation and removal.
3Reliability
If protruding grommets are used to retain vane tips, then the vane tips are secured, but the grommets disturb the airflow and alter engine performance
Solution Approach 1:
The grommet is designed with smooth curved surfaces and rounded contours that allow airflow to flow over it smoothly. This streamlined shape minimizes turbulence and drag caused by the grommet's presence, reducing airflow disturbance while maintaining vane tip retention functionality.
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 solution effectively retains vane tips, reduces damage risk, simplifies installation and maintenance, and improves airflow smoothness by eliminating the need for adhesives and enhancing stability against foreign object impacts.
Implementation Method 1
a flexible grommet with tongues and a slit, which eliminates the need for adhesives by using airflow to maintain grommet position
Implementation Method 2
using airflow to maintain grommet position
Data Source
AI summary
A vane assembly (20) for a gas turbine engine including a shroud (26) with openings (54) defined therein about a circumference thereof and vanes (22) extending radially from the shroud (26) with a vane tip (24) in each opening (54). Isolating means (28) are disposed in each opening (54) to isolate the vane tip (24) from the shroud ring (34). Each vane tip (24) is engaged with the shroud (26) by retaining means (38) for restricting movement of the vane tip (24) in an axial direction relative to said shroud (26).