Circumferential Seal Assembly Using Duct-Fed Grooves Against Oil Backflow
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Solution Overview
Problem
Existing 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.
Innovation Solution
A circumferential sealing assembly that incorporates ducts communicating with grooves on a rotatable runner or sleeve, directing hot gas to form a hydrodynamic flow and prevent backflow, thereby maintaining a thin film between sealing surfaces to prevent lubricant migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If grooves are used to form a thin film between sealing surfaces, then sealing performance is improved, but backflow occurs along the grooves causing lubricant migration
Solution Approach 1:
The sealing ring is divided into multiple segments with grooves between them, creating segmented sealing zones. Each groove acts as an independent hydrodynamic bearing zone that generates positive pressure to prevent backflow, while the segmentation allows controlled flow paths that eliminate harmful lubricant migration to the high-pressure side
Solution Approach 2:
The grooves act as intermediary elements between the sealing surfaces, introducing gas as a mediator substance. The gas forms a hydrodynamic film within the grooves that separates the lubricant from the high-pressure gas side, preventing direct contact and backflow while maintaining sealing integrity
2Reliability
If circumferential sealing is used to separate lubricant and hot gas, then separation is achieved, but mixing occurs due to backflow along grooves
Solution Approach 1:
The invention utilizes gas-pneumatic principles by introducing gas into the grooves to create hydrodynamic pressure zones. This pneumatic action generates sufficient pressure to counteract the high-pressure gas side, preventing backflow and maintaining stable separation between lubricant and hot gas without mixing
Solution Approach 2:
The grooves are designed to rotate with the runner, creating dynamic hydrodynamic conditions. The rotation generates continuous gas flow patterns within the grooves that adapt to operating conditions, maintaining stable separation and preventing mixing under varying pressure and speed conditions
3Strength
If a thin film is formed between sealing surfaces, then wear is reduced, but backflow prevents stable film maintenance
Solution Approach 1:
The grooves are pre-configured to generate hydrodynamic pressure before significant lubricant migration can occur. The geometry and positioning of the grooves ensure that gas pressure is established in advance to counteract backflow forces, maintaining stable thin film conditions and preventing surface contact wear from the outset
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 prevents backflow and mixing between lubricant oil and hot gas, reducing the risk of oil coking and engine fires by maintaining a stable sealing interface.
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
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
Implementation Method 3
The thin film resists migration of the lubricant from the lower-pressure side to the higher-pressure side
Data Source
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.