Circumferential Seal Assembly With Self-Adjusting Seating Forces
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Solution Overview
Problem
Turbine engines face challenges in maintaining effective sealing at higher shaft speeds and pressures, leading to excessive wear, heating, and potential fluid mixing between compartments, which can result in engine issues like fires and lubricant loss.
Innovation Solution
A circumferential seal assembly comprising a primary sealing ring, a second sealing ring, and a third sealing ring, along with a ring-shaped insert, which defines cavities to manage pressure differentials and fluid flow, minimizing leakage and contact forces through optimized channel and groove configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If higher shaft speeds and pressures are used to enhance turbine engine performance, then power and efficiency are improved, but sealing effectiveness deteriorates leading to excessive wear, heating, and fluid mixing
Solution Approach 1:
The seal assembly is divided into multiple sealing rings (primary sealing ring, second sealing ring, third sealing ring) that work together to address different aspects of the sealing challenge. Each ring handles specific pressure differentials and fluid flows, distributing the sealing workload and improving overall reliability at high speeds and pressures
Solution Approach 2:
A ring-shaped insert is introduced as an intermediary component between the sealing rings and the housing. This insert defines cavities and manages pressure differentials, acting as a mediator that stabilizes the sealing environment and prevents fluid mixing between compartments under extreme operating conditions
2Device complexity
If traditional single-seal designs are used, then device complexity is low, but wear and heating on sealing surfaces become excessive at high pressures and speeds
Solution Approach 1:
The sealing function is segmented across multiple rings rather than relying on a single seal. This segmentation reduces the wear and heating burden on any individual sealing surface while maintaining effective sealing, as each ring handles a portion of the total sealing requirement
Solution Approach 2:
The invention utilizes fluid pressure differentials and hydrodynamic principles to manage sealing forces. By directing fluid flows and utilizing pressure differentials across the sealing rings, the system reduces direct contact and friction, thereby minimizing wear and heating on sealing surfaces
3Reliability
If multiple sealing rings and cavities are added to manage pressure differentials, then sealing effectiveness improves, but device complexity increases
Solution Approach 1:
The ring-shaped insert serves multiple functions simultaneously: it defines cavities for pressure management, provides structural support for the sealing rings, and directs fluid flows. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity while improving sealing effectiveness
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 minimizes wear and heating on sealing surfaces, reduces coolant requirements, and maintains effective sealing, even at extreme conditions, by self-adjusting force balances and redirecting fluid flows to prevent fluid mixing between compartments.
Implementation Method 1
A garter spring is positioned about the primary sealing ring so as to apply an elastic force onto the primary sealing ring in the direction of the radial sealing surface
Implementation Method 2
A coil spring is positioned at one side of the primary sealing ring so as to apply an elastic force onto the primary sealing ring in the direction of the face sealing surface
Implementation Method 3
A forward pressure is communicated across the forward face via a fluid contacting the primary sealing ring. The forward pressure imparts a forward face force in the direction of the higher pressure side
Implementation Method 4
Each seal segment includes a vertical flange at one end of a horizontal flange so that the vertical flange sealingly engages the face sealing surface
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
A circumferential seal assembly (30) for use between a higher pressure side (36) and a lower pressure side (37) is presented. The seal assembly (30) includes a primary sealing ring (31), a second sealing ring (32), a third sealing ring (33), and an insert (34). The segmented primary sealing ring (31) sealingly engages both a face sealing surface (46) along a housing (35) and a radial sealing surface (45) along a rotatable element (52). The insert (34) is disposed within and directly contacts the housing (35). The second sealing ring (32) is adjacent to the primary sealing ring (31) and sealingly engages both the primary sealing ring (31) and the insert (34). The segmented third sealing ring (33) contacts and sealingly engages the primary sealing ring (31) opposite the housing (35). The insert (34), the second sealing ring (32), and the third sealing ring (33) cooperate to form a first cavity (53) adjacent to the second sealing ring (32) and the third sealing ring (33). The primary sealing ring (31), the second sealing ring (32), the insert (34), and the housing (35) cooperate to form a second cavity (54) adjacent to the primary sealing ring (31). The insert (34) and the second sealing ring (32) separate the first cavity (53) from the second cavity (54).