Blade Outer Air Seal with Integrated Air Shield for Thermal Management
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Solution Overview
Problem
Gas turbine engines face performance issues due to unintended clearance changes between rotating blades and the casing, caused by high heat transfer leading to thermal expansion, which existing solutions attempt to mitigate with added mass but with limited effectiveness and increased weight.
Innovation Solution
A blade outer air seal design featuring a substrate extending axially across the seal body, with plasma-sprayed rotor rub strips and axially spaced channels that form cavities to break thermal conduction paths, reducing thermal gradients and eliminating the need for added mass to control thermal response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mass is added to the case to slow the case response, then the clearance stability is improved, but the engine weight increases
Solution Approach 1:
An air shield is introduced as an intermediary component between the gas path and the case flange. The air shield acts as a thermal barrier that reduces heat transfer to the case, thereby slowing thermal expansion and improving clearance stability without adding significant mass to the case structure.
Solution Approach 2:
The air shield functions as a thin thermal barrier that effectively reduces heat conduction. By using a thin air-filled barrier rather than thick solid material, the solution achieves thermal insulation while minimizing weight addition.
2Reliability
If the case is positioned in close proximity to the blade tip to seal, then the sealing effectiveness is improved, but the thermal heat transfer to the case increases
Solution Approach 1:
The air shield serves as a thermal intermediary that decouples the thermal interaction between the gas path and the case flange. This allows the case to remain in close proximity to the blade tip for effective sealing while the air shield absorbs and blocks the thermal energy, preventing excessive case temperature rise.
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 reduces thermal gradients and extends the low cycle fatigue life of the seal by insulating the flange from the gas path, achieving lower temperatures and maintaining desired clearances without increasing engine weight.
Implementation Method 1
cavities to break thermal conduction paths, reducing thermal gradients and eliminating the need for added mass to control thermal response
Implementation Method 2
the rotor rub strip is plasma sprayed onto the substrate
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A blade outer air seal (70) includes a seal body (75) extending circumferentially about an axis (A) and including at least one channel (76) having a substantially solid radially outer surface. A substrate (78) is radially inward of the at least one channel (76) with respect to the axis (A). The substrate (78) and the at least one channel (76) form at least one cavity (82). A rotor rub strip (72) is radially inward of the substrate (78).