Low-Density Abradable Seal With Radial-Wall Deflection Resistance
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Solution Overview
Problem
Low density abradable seals in gas turbine engines deflect during operation due to engine backpressure, leading to increased contact with the rotor and potential overheating.
Innovation Solution
An abradable seal comprising a stator substrate with a casing and radial walls, coupled with a low density abradable material containing embedded hollow microspheres, providing a high elastic modulus ratio to resist deflection and featuring a thermoplastic casing for stiffness, along with optional channels to prevent heat buildup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If low density abradable material is used to reduce heat generation during rub events, then heat generation is reduced, but the seal material deflects under engine backpressure causing increased contact with the rotor
Solution Approach 1:
The seal uses a composite structure combining low density abradable material (for heat reduction) with a stiffer support structure (casing with radial walls) to prevent deflection. The composite design allows each material to perform its optimal function: the abradable material reduces heat during rub events while the supporting casing maintains structural stability under backpressure.
Solution Approach 2:
The seal is divided into functional segments: the abradable seal material portion that contacts the rotor and reduces heat, and the separate casing with radial walls that provides structural support and prevents deflection. This segmentation allows optimization of each portion for its specific function without compromise.
2Temperature
If precut trenches are added to improve heat transfer, then heat transfer is improved, but the elastic modulus decreases causing increased deflection
Solution Approach 1:
The heat transfer function is separated from the structural support function. Precut trenches are added to the abradable material portion to enhance heat transfer, while the separate casing with radial walls provides the structural strength and elastic modulus needed to prevent deflection. The segmentation allows both features to coexist without compromising overall performance.
3Ease of manufacture
If the seal material is made softer to improve abradability, then abradability is improved, but the seal deflects more under gas loads
Solution Approach 1:
The seal employs a composite structure where the softer abradable material provides improved abradability and heat reduction, while the stiffer casing with radial walls compensates for the reduced structural integrity. The composite design allows the seal material to be optimized for abradability without sacrificing overall structural stability under gas loads.
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 seal effectively resists deflection and reduces heat generation during rub events, enhancing engine efficiency and preventing additional contact with the rotor.
Implementation Method 1
the abradable material comprises a silicone material with imbedded hollow microspheres; the abradable material comprises a density of from about 0.5 to about 0.65 grams/cubic centimeter
Implementation Method 2
said casing and said abradable material comprising a ratio of elastic modulus of casing to abradable of about 50-5000X in order to resist a deflection responsive to engine gas loads
Implementation Method 3
Knife edge seals present issues during rub events as heat generated between the rotor tip and the seal material dramatically increases the temperature of the seal and associated rotor tip
Data Source
Figure 1
Figure 2~3
AI summary
A hybrid abradable seal including a stator substrate having an external surface; a casing coupled to the external surface, the casing including radial walls extending radially from the external surface; an abradable material disposed within the casing; the abradable material and the casing being coupled together and configured to resist a deflection responsive to engine gas loads.