Blade Outer Air Seal Angular Offset for Hot Gas Ingestion
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Solution Overview
Problem
Gas turbine engines face inefficiencies due to uncontrolled pressure differentials and hot gas ingestion at the blade outer air seals, leading to increased cooling air requirements and potential distress on the seal segments.
Innovation Solution
An annular arrangement of outer air seal segments with intersegment gaps angularly offset relative to the longitudinal axis of the engine, stabilizing pressure differentials and reducing hot gas ingestion by aligning the gap with the blade's mean camber line, allowing targeted cooling and reduced hot gas penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If outer air seal segments are arranged in an annular configuration with intersegment gaps, then the seal assembly can accommodate blade tip motion and maintain sealing effectiveness, but uncontrolled pressure differentials and hot gas ingestion occur at the gap locations
Solution Approach 1:
The intersegment gaps are angularly offset relative to the longitudinal axis rather than being symmetrically aligned. This asymmetric positioning causes the gaps to be located at specific angular positions where the blade mean camber line passes through, thereby controlling hot gas ingestion while maintaining sealing effectiveness.
Solution Approach 2:
The seal assembly has different characteristics at different locations. The intersegment gaps are strategically positioned at specific angular offsets where the blade mean camber line intersects, creating localized regions with different flow characteristics. This allows controlled hot gas ingestion at specific locations while maintaining overall sealing effectiveness.
2Reliability
If cooling air is increased to cool the seal segments, then the segments are protected from hot gas distress, but engine efficiency decreases due to excessive cooling air requirements
Solution Approach 1:
The patent converts the potentially harmful effect of hot gas ingestion into a beneficial cooling effect. By positioning the intersegment gaps at specific angular offsets where the blade mean camber line passes through, the design allows controlled hot gas flow through the gaps to cool the seal segments, thereby protecting them from overheating while reducing the need for excessive cooling air.
Solution Approach 2:
The seal assembly uses its own structural features (the intersegment gaps positioned at specific locations) to provide self-cooling. The gaps are positioned to allow hot gas flow that naturally cools the segments, eliminating the need for separate cooling systems or excessive cooling air supply.
3Object-affected harmful factors
If intersegment gaps are angularly offset with respect to the longitudinal axis, then hot gas ingestion is reduced and pressure differentials are stabilized, but the manufacturing precision requirements increase
Solution Approach 1:
The patent changes the angular position parameter of the intersegment gaps relative to the longitudinal axis. By specifying precise angular offsets, the design controls hot gas ingestion and stabilizes pressure differentials. This parameter change requires manufacturing precision in the angular positioning of the gaps.
Data Source
AI summary
Gas turbine engines and related systems involving blade outer air seals are provided. In this regard, a representative blade outer air seal segment for a set of rotatable blades includes: a blade arrival end; and a blade departure end; each of the blade arrival end and the blade departure end being angularly offset with respect to a longitudinal axis about which the blades rotate.