Segmented Active Clearance Control for Turbine Blade Gap
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Solution Overview
Problem
The gap between the Blade Outer Air Seals (BOAS) and the turbine blades in aircraft engines becomes inconsistent due to expansion and uneven wear, leading to decreased turbine efficiency.
Innovation Solution
An active clearance control (ACC) system comprising a ring with segments, supply lines, and flow control assemblies that meter cool air to adjust the gap between the BOAS and turbine blades, using cool air to contract the case assembly and reduce the gap size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the case assembly is allowed to expand during operation, then the turbine can operate at higher temperatures and maintain structural integrity, but the gap between the BOAS and turbine blade tips increases, decreasing turbine efficiency
Solution Approach 1:
The patent applies parameter changes by introducing a temperature-dependent clearance control mechanism. Flow control assemblies adjust the amount of cooling air delivered to different zones of the case assembly, dynamically changing the thermal state of the case to maintain optimal clearance between the BOAS and turbine blade tips across varying operating temperatures
Solution Approach 2:
The patent directly addresses thermal expansion by using controlled thermal contraction. Cooling air is directed to specific zones of the case assembly to induce localized thermal contraction, counteracting the natural thermal expansion that would otherwise increase the gap between the BOAS and turbine blade tips
2Productivity
If the gap between the BOAS and turbine blade tips is reduced to maintain turbine efficiency, then turbine performance is improved, but the case assembly may experience excessive thermal stress or deformation
Solution Approach 1:
The patent applies local quality by dividing the case assembly into multiple thermal zones, each with independent flow control assemblies. This allows different regions of the case to have different thermal characteristics and contraction levels, maintaining structural integrity while achieving the necessary clearance reduction in critical areas
Solution Approach 2:
The case assembly is segmented into multiple zones with independent cooling control. Each zone can be cooled to a different extent, allowing the system to maintain overall structural integrity while creating localized contraction to reduce critical clearances
3Device complexity
If a uniform cooling system is used around the case assembly, then the system structure is simple, but it cannot address the non-uniform gap variations that occur after break-in period
Solution Approach 1:
The cooling system is segmented into multiple independent zones, each with its own flow control assembly. This segmentation allows precise control of cooling in each zone to compensate for non-uniform gap variations, while the modular design keeps overall system complexity manageable
Solution Approach 2:
Each zone of the case assembly receives customized cooling based on its specific clearance requirements. The flow control assemblies are adjusted to provide different cooling levels to different zones, addressing local gap variations with targeted thermal contraction
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 ACC system effectively reduces the gap between the BOAS and turbine blades, enhancing turbine efficiency by using cool air to shrink the case assembly circumference.
Implementation Method 1
using cool air to contract the case assembly and reduce the gap size
Data Source
AI summary
An ACC system and method of using such for changing a turbine blade to BOAS gap on an aircraft engine is disclosed. The ACC system may comprise a first ring, a first supply line and a first flow control assembly. The first ring may be configured to substantially encircle a portion of a case assembly that is disposed around an aircraft engine turbine. The first ring may include a plurality of segments that each define a chamber, an inlet port and a plurality of outlet ports. At least a portion of the outlet ports may be configured to be disposed adjacent to the case. The first supply line may be operatively connected to a first segment of the plurality of segments. The first flow control assembly may be operatively connected to the first supply line and configured to meter the flow of cool air into the first segment.