Turboexpander Labyrinth Seal With Progressive Pressure Venting
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Solution Overview
Problem
Current labyrinth seal configurations for turboexpanders are not efficient enough in reducing gas leakage, leading to significant losses of high-pressure process gas, which is valuable and costly.
Innovation Solution
The proposed solution involves a labyrinth seal design with a series of external teeth on a rotating shaft and a surrounding stationary seal with inner openings that direct leaked gas through a series of flow channels and vent ports, allowing for progressive pressure reduction and recovery of gas at different stages, minimizing net loss to the atmosphere.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional labyrinth seal is used to prevent gas leakage around the rotating shaft, then the structure is simple and easy to manufacture, but gas leakage is significant and energy loss is high
Solution Approach 1:
The labyrinth seal is divided into multiple segments or sections along the axial direction, with each segment having its own set of teeth and gaps. This segmentation allows the seal to create multiple pressure zones, progressively reducing gas pressure and leakage flow, thereby improving energy efficiency while maintaining a modular structure that is not excessively complex
Solution Approach 2:
The invention introduces a multi-dimensional approach by creating three-dimensional flow paths through the labyrinth structure, utilizing both axial and radial dimensions. The gas flow is forced to navigate through complex three-dimensional passages rather than simple linear gaps, significantly reducing leakage without requiring excessive structural complexity
2Loss of energy
If the clearance between labyrinth teeth and running surface is reduced to improve sealing, then gas leakage decreases, but friction increases and the seal life decreases
Solution Approach 1:
The labyrinth seal uses a series of partial sealing actions through multiple teeth and gaps rather than relying on a single tight clearance. Each tooth-gap pair provides partial sealing, and the cumulative effect of multiple such pairs achieves significant leakage reduction without requiring any single clearance to be excessively small, thus avoiding high friction and wear
Solution Approach 2:
The labyrinth teeth act as intermediary elements between the high-pressure gas source and the low-pressure region. Instead of creating a direct tight seal, the teeth provide intermediate pressure zones that gradually reduce gas pressure, serving as mediators that reduce leakage without requiring direct contact or minimal clearance that would cause wear
3Loss of energy
If a labyrinth seal with multiple teeth is used to reduce gas leakage, then sealing performance improves, but the manufacturing complexity and cost increase
Solution Approach 1:
The labyrinth seal structure is designed to serve multiple functions simultaneously: it provides sealing, pressure reduction, and flow control all through the same basic tooth-gap geometry. This multi-functionality allows the use of standard manufacturing processes for creating the teeth, improving ease of manufacture while achieving effective leakage reduction through the combined effect of multiple teeth
Solution Approach 2:
The invention optimizes key parameters such as tooth height, gap width, and number of teeth to achieve the desired sealing performance. By carefully selecting these parameters within practical manufacturing ranges, the seal achieves effective leakage reduction without requiring extreme or difficult-to-manufacture dimensions, thus maintaining ease of manufacture
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 design effectively reduces gas leakage by recovering and recycling gas at progressively lower pressures, minimizing the amount of gas lost to the atmosphere and optimizing energy usage in the recovery process.
Implementation Method 1
Each set of inner openings leads to a flow channel common to those inner openings and ported to a location separate from the other flow channels. When high pressure gas at the high pressure end of the axial segment leaks between the inner lumen of the labyrinth seal and the teeth and reaches the first set of inner openings, the high pressure gas is ported to a first recovery location. When medium pressure gas leaks between the inner lumen of the labyrinth seal and the teeth to reach a second set of inner openings in series with the first set of inner openings, the medium pressure gas is ported to a second recovery location.
Data Source
AI summary
There is disclosed a labyrinth seal arrangement for gas turboexpanders and the like which reduces process gas losses. The labyrinth seal includes a plurality of axially spaced seal sets with teeth facing a seal member. A plurality of vent ports in between each seal set permits extraction of gradually lower pressure process gas.