Blade Outer Air Seal Cooling Air Distribution
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Solution Overview
Problem
Existing blade outer air seal (BOAS) configurations face challenges in evenly distributing cooling air due to pressure gradients, leading to excessive flow through some holes and insufficient flow through others, despite attempts to tailor air distribution to isolated fore and aft chambers.
Innovation Solution
The BOAS configuration is reengineered by dividing quadrant chambers into separate upstream and downstream regions with partial restrictions, using channels and ribs to create distinct pressure zones and optimize hole distribution, ensuring effective air flow and pressure differences between regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cooling air is fed into a plenum and passes through passageways in the seal body, then the ID face can be film cooled, but air flow distribution becomes uneven due to pressure gradients causing excessive flow through some holes and insufficient flow through others
Solution Approach 1:
The seal body is divided into multiple independent cooling chambers (first cooling chamber and second cooling chamber) separated by a partition wall. Each chamber has its own set of cooling holes, allowing independent control of air flow to different regions. This segmentation eliminates the pressure gradient problem in a single large plenum by creating smaller, isolated cooling zones where air distribution can be more uniform.
Solution Approach 2:
Different regions of the seal body are provided with different cooling configurations - the first cooling chamber serves the leading edge region while the second cooling chamber serves the trailing edge region. Each chamber can be optimized independently for its specific location's cooling requirements, allowing local adaptation of cooling intensity and hole distribution to achieve uniform overall cooling.
2Temperature
If air is bled to cool feather seal segments at circumferential ends, then adjacent BOAS segments can be cooled, but total air requirements increase
Solution Approach 1:
The cooling function for both the BOAS ID face and the adjacent feather seal segments is integrated into a single chamber structure. The first and second cooling chambers are positioned such that they simultaneously cool the seal body and provide cooling air to the feather seal segments through shared passageways and outlet holes, eliminating the need for separate bleeding systems.
Solution Approach 2:
The cooling chambers and passageways are designed to serve multiple functions: they cool the ID face of the seal body through film cooling holes, cool the feather seal segments through circumferential outlet holes, and maintain structural integrity. This multi-functionality reduces the total air requirement by using the same cooling air for multiple cooling purposes.
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
This approach allows for improved air flow distribution, maintaining desired pressures in each region and minimizing total air requirements for effective cooling, while avoiding interference with local cooling and potential rubbing issues.
Implementation Method 1
The cooling air may pass through passageways in the seal body and exit outlet ports in the inboard or inner diameter (ID) side of the body (e.g. to film cool the ID face)
Implementation Method 2
Air may also exit along the circumferential ends (matefaces) of the BOAS so as to be vented into the adjacent inter-segment region (e.g., to help cool feather seal segments sealing the adjacent BOAS segments)
Data Source
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AI summary
A turbine engine blade outer air seal segment (20) has a body (22) having a base portion (50). The base portion (50) has a transversely concave ID face (32), a forward end (24), an aft end (26), and first and second circumferential edges (28, 30) The body (22) has at least one mounting hook (42). At least one cover plate (60) is secured to the body (22) to define at least one cavity (90....93). The cover plate (60) has a plurality of feed holes (64). A plurality of outlet holes (70) extend through the base portion (50) to the ID face (32). At least one of the base portion (50) and cover plate (60) comprises a protruding portion protruding into the cavity to form a partial restriction (118) separating circumferentially and fore-aft offset cavity portions.