Impeller Seal Gas Layout for Thrust Reduction in Rotating Machines
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Solution Overview
Problem
Strong thrust forces in rotating machines, such as centrifugal compressors, increase the load on thrust supporting members, necessitating higher sliding resistance and stronger components, which can lead to inefficiencies and increased costs.
Innovation Solution
The implementation of a rotating machine design that includes a rotary shaft, an impeller, a casing, a first seal portion, a second seal portion, a gas supply path, and a gas outflow path, where the seal gas is introduced and allowed to flow out to a pressure space lower than the seal gas, reducing the thrust force acting on the impeller, and optionally using the working fluid as the seal gas to reduce costs and enhance energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the thrust force is strong, then the impeller can effectively compress the fluid, but the load on the thrust supporting member increases
Solution Approach 1:
The patent extracts the harmful thrust force component by introducing seal gas into the seal portion between the impeller and casing. This creates a counteracting pressure that balances the fluid pressure acting on the impeller, effectively removing the net thrust force from the system while preserving the impeller's fluid compression function
Solution Approach 2:
The seal gas acts as an intermediary substance introduced into the seal portion. It mediates between the high-pressure fluid acting on the impeller and the low-pressure environment, creating a balancing pressure that reduces the thrust force transmitted to the thrust supporting member without interfering with the impeller's primary compression function
2Strength
If the thrust supporting member is made stronger to support higher thrust force, then the thrust force can be supported, but the sliding resistance increases
Solution Approach 1:
The patent applies preliminary action by introducing seal gas into the seal portion before the impeller rotates under full load. This pre-establishes a pressure balance that reduces the thrust force on the thrust supporting member, allowing the use of lighter-duty bearings with lower sliding resistance while still supporting the operational loads
3Reliability
If a separate seal gas is used, then the seal portion can function properly, but the cost increases
Solution Approach 1:
The patent applies universality by enabling the working fluid to serve dual functions: as the process fluid being compressed and as the seal gas for the seal portion. This eliminates the need for separate seal gas supply systems and reduces material quantity requirements while maintaining reliable sealing function
Solution Approach 2:
The system applies self-service by using the working fluid itself to provide the sealing function. The working fluid automatically serves as the seal gas, eliminating the need for external seal gas supply and reducing system complexity and costs
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 effectively reduces the thrust force acting on the rotating machine, decreasing the load on thrust bearings and improving operational efficiency while minimizing the need for separate seal gases, thus reducing costs and enhancing energy utilization.
Implementation Method 1
a gas outflow path that is provided in the second seal portion and communicates with a pressure space having a pressure lower than that of the seal gas to allow at least some of the seal gas to flow out from the first seal portion to the pressure space
Data Source
AI summary
A rotating machine includes: a rotary shaft that is configured to rotate about a center axis; an impeller that is fixed to the rotary shaft and that is configured to compress a working fluid by integrally rotating with the rotary shaft; a casing that covers the rotary shaft; a first seal portion that is disposed at a position away from the impeller in a center axis direction of the rotary shaft and that is configured to seal a portion between the rotary shaft and the casing with a seal gas; a second seal portion that is disposed between the impeller and the first seal portion and that is configured to seal a portion between the rotary shaft and the casing; and a gas supply path through which the seal gas is introduced into the first seal portion.