Circumferential Seal Grooves Using Duct-Fed Gas to Prevent Backflow

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Solution Overview

Problem

Circumferential sealing assemblies in gas turbine applications face challenges with backflow along grooves, leading to mixing between lubricant oil and hot gas, which increases the risk of oil coking and engine fires, as existing groove-fed sealing methods do not consistently prevent backflow effectively.

Innovation Solution

The implementation of a circumferential sealing assembly that includes a rotatable runner and a sealing ring with grooves and ducts, where the ducts communicate with the grooves to direct hot gas and form a hydrodynamic flow, preventing backflow and maintaining a thin film between the sealing surfaces to isolate the lubricant from the hot gas.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If grooves are used along the sealing surface to direct gas flow, then sealing performance is improved by forming a thin film, but backflow occurs along the grooves leading to mixing between lubricant and hot gas

Engineering Contradiction:

Improvesealing performanceVSAvoidbackflow and mixing

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The sealing surface is segmented into multiple discrete grooves rather than a continuous groove, allowing individual control of gas flow paths. Each groove acts as an independent hydrodynamic bearing, preventing continuous backflow paths while maintaining sealing effectiveness through distributed gas film formation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of allowing gas to enter grooves from the high-pressure side and flow naturally, the invention introduces gas through ducts from the low-pressure side, reversing the conventional gas flow direction. This inversion creates hydrodynamic pressure that pushes gas toward the high-pressure side, preventing backflow of lubricant while maintaining the sealing film.

Inventive Principle:

Principle #13The other way round (Inversion)

2Ease of manufacture

If a thin film is formed between sealing surfaces to reduce wear, then frictional wear is reduced, but mixing between lubricant oil and hot gas increases

Engineering Contradiction:

Improvereduced wearVSAvoidmixing between lubricant and gas

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

The patent introduces hot gas through ducts as an intermediary substance that fills the space between the sealing surfaces. This gas mediator creates a hydrodynamic film that separates the lubricant from the hot gas compartments while maintaining the thin film necessary for reduced wear, preventing direct contact and mixing between lubricant and hot gas.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 solution effectively prevents backflow and mixing between lubricant oil and hot gas, reducing the risk of oil coking and engine fires by maintaining a consistent hydrodynamic flow and thin film seal, thereby enhancing the sealing integrity and reducing frictional wear.

Implementation Method 1

The hot gas entering the grooves in use via the ducts in combination with rotation of the grooves with the rotatable runner cause the hot gas to form a hydrodynamic flow within the grooves

Methodology Applied

Scientific EffectHydrodynamic flow: Hydrodynamic Cavitation

Implementation Method 2

The grooves redirect the hot gas in the direction of the inner sealing surface to form a thin film between the outer sealing surface and the inner sealing surface

Methodology Applied

Scientific EffectHydrodynamic lubrication: Lubrication

Data Source

PatentUS11635146B2Circumferential sealing assembly with duct-fed hydrodynamic grooves

Publication Date: 2023.04.25 STEIN SEAL CO

AI summary

A circumferential sealing assembly for use between a lower-pressure side with a lubricant oil therein and a higher-pressure side with a hot gas therein is presented. The assembly includes a sealing ring interposed between either a rotatable runner and a housing or a sleeve and a housing within a turbine engine. Ducts communicate the hot gas into grooves to form a thin film between the ring and the runner or the ring and the sleeve. First embodiments include grooves on the runner, ducts through the runner, and both grooves and ducts rotating with the runner. Second embodiments include grooves on the ring, ducts through the runner, and ducts rotating with the runner. Third embodiments include grooves on the ring and ducts through the ring adjacent to a runner. Fourth embodiments include grooves on the runner, ducts through the ring, and grooves rotating with the runner. Fifth embodiments include grooves on the sleeve, ducts through the sleeve, and both grooves and ducts rotating with the sleeve. Sixth embodiments include grooves on the ring, ducts through the sleeve, and ducts rotating with the sleeve. Seventh embodiments include grooves on the ring and ducts through the ring adjacent to a sleeve. Eighth embodiments include grooves on the sleeve, ducts through the ring, and grooves rotating with the sleeve.