Hydrostatic Face Seal with Honeycomb Backup for Gas Turbines
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Solution Overview
Problem
Labyrinth seals in gas turbine engines deteriorate over time due to thermal and mechanical growths, assembly tolerances, and engine loads, leading to increased parasitic losses and thermodynamic cycle losses.
Innovation Solution
The implementation of hydrostatic face seals with integrated back-up seals, where a stator assembly with a honeycomb labyrinth-type back-up seal and a rotor assembly with knife edges maintain pressure differentials, ensuring continued operation even if the primary hydrostatic seal fails by shifting the pressure differential to the back-up seal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If labyrinth seals are used to maintain pressure differentials, then the seal structure is simple and easy to manufacture, but the seal deteriorates over time due to thermal and mechanical growths, assembly tolerances, and engine loads
Solution Approach 1:
The seal system is divided into two independent segments: a primary hydrostatic seal and a secondary labyrinth seal. Each segment performs the sealing function independently, allowing the primary seal to operate under optimal conditions while the backup seal provides redundancy. This segmentation resolves the contradiction by maintaining manufacturing simplicity through modular design while significantly improving reliability through fail-safe architecture.
Solution Approach 2:
The backup labyrinth seal is pre-positioned and pre-configured to automatically engage when the primary hydrostatic seal deteriorates or fails. This beforehand cushioning ensures that when thermal and mechanical growths, assembly tolerances, or engine loads cause primary seal deterioration, the backup seal is already in place to maintain pressure differentials, thereby improving reliability without complicating the manufacturing process.
2Reliability
If a backup seal is added to protect against primary seal failure, then reliability is improved, but device complexity increases
Solution Approach 1:
The backup labyrinth seal structure is designed to serve multiple functions: it acts as a backup sealing mechanism, provides structural support, and maintains pressure differentials. By making the backup seal multi-functional, the patent improves reliability while minimizing the increase in device complexity, as the same structural elements serve multiple purposes rather than requiring additional dedicated components.
Solution Approach 2:
The backup seal is designed as a simple, robust labyrinth structure that is easier and less expensive to manufacture than the primary hydrostatic seal. When the primary seal fails, the backup seal takes over, and the system continues operation until the next maintenance interval. This approach improves reliability while keeping the added complexity minimal, as the backup seal is intentionally designed to be simpler and more replaceable.
3Reliability
If the primary hydrostatic seal fails, then continued operation is possible with backup seal, but parasitic losses increase
Solution Approach 1:
When the primary hydrostatic seal fails, the system rapidly transitions to the backup labyrinth seal configuration. The backup seal maintains pressure differentials sufficiently to allow the engine to continue operating in a degraded mode until the next maintenance interval. This skipping principle allows the system to rush through the failure state without complete shutdown, accepting temporary increased parasitic losses while maintaining operational continuity and reliability.
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 configuration minimizes damage from unintended contact and maintains efficient pressure differentials across the gas turbine engine, reducing parasitic losses and extending the seal's lifespan by providing a backup mechanism during failure modes.
Implementation Method 1
a hydrostatic seal uses balanced opening and closing forces to maintain a desired separation between a seal face and a corresponding seal runner
Implementation Method 2
a stator assembly with a honeycomb labyrinth-type back-up seal and a rotor assembly with knife edges maintain pressure differentials
Data Source
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AI summary
A seal assembly for a gas turbine engine includes: a stator assembly (16) and a rotor assembly (18) configured to operatively engage each other to form a first seal (12) and a second seal (14); the first seal (12) being provided by a hydrostatic seal (12) having a seal face (24) and a seal runner (26); and the second seal (14) being provided by a back-up seal such that responsive to a failure of the first seal (12), the back-up seal (14) maintains at least a portion of a pressure differential established by the first seal (12) prior to the failure.