Compressor Balance Piston Seal Centering

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Solution Overview

Problem

Conventional compact compressors face efficiency reduction and potential damage due to thermal expansion and centrifugal forces causing misalignment of balance piston seals, leading to eccentric rotation and leakage, especially at high compression ratios.

Innovation Solution

A balance piston seal assembly with a stationary support and gripping assembly that secures the balance piston seal to the compressor casing, maintaining concentricity during thermal expansion and radial growth, preventing misalignment and leakage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the impeller rotates at high speeds to achieve higher compression ratios, then the compression ratio is improved, but thermal expansion and centrifugal forces cause misalignment of the balance piston seal

Engineering Contradiction:

Improvecompression ratioVSAvoidalignment of balance piston seal

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The balance piston seal is designed with radial flexibility, allowing it to dynamically adjust its position in response to thermal expansion and centrifugal forces during high-speed rotation. The seal can expand radially outward while maintaining concentric alignment through its flexible structure, rather than being rigidly constrained.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The balance piston seal's physical parameters (particularly its radial dimensions) are allowed to change in response to thermal and centrifugal conditions. The seal's material properties enable controlled thermal expansion that maintains alignment rather than causing misalignment, adapting the seal's geometry to operating conditions.

Inventive Principle:

Principle #35Parameter changes

2Temperature

If the balance piston seal is allowed to expand radially during thermal expansion, then the seal can accommodate high-speed operation, but misalignment and eccentric rotation occur

Engineering Contradiction:

Improvethermal expansion accommodationVSAvoidconcentricity of balance piston seal

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The balance piston seal is specifically designed to utilize thermal expansion as a beneficial mechanism. The seal's material and structural design allow it to expand radially in a controlled manner that maintains concentric alignment with the balance piston, rather than resisting expansion which would cause misalignment.

Inventive Principle:

Principle #37Thermal expansion

Solution Approach 2:

The balance piston seal employs an asymmetric cross-sectional design with different thicknesses at different radial positions. This asymmetric geometry enables differential expansion patterns that maintain overall concentricity while accommodating thermal growth, preventing eccentric rotation during high-temperature operation.

Inventive Principle:

Principle #4Asymmetry

3Device complexity

If conventional balance piston seals are used, then the structure is simple, but leakage increases due to misalignment at high compression ratios

Engineering Contradiction:

Improveseal structure simplicityVSAvoidleakage through radial clearances

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The balance piston seal is divided into multiple segmented elements or lobes that can independently adjust their positions. This segmentation allows each element to maintain optimal alignment with the balance piston surface, minimizing leakage paths while keeping the overall structure relatively simple and avoiding complex mechanical alignment systems.

Inventive Principle:

Principle #1Segmentation

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 maintains concentricity and alignment between the balance piston seal and the balance piston, enhancing operational efficiency and preventing damage by securing the seal during thermal and centrifugal expansions, thus improving the compressor's performance and longevity.

Implementation Method 1

the thermal energy generated from the compression of the process fluid may also cause the thermal expansion of the balance piston seal

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

thermal energy (e.g., heat of compression) and/or centrifugal forces may cause the impeller and the balance piston to expand or grow radially outward

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Data Source

PatentEP3274591B1Compressor with a balance piston seal centering

Publication Date: 2020.12.23 DRESSER RAND CO

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AI summary

A balance piston seal assembly for a balance piston of a compressor is provided. The balance piston seal assembly may include a balance piston seal, a stationary support, and a gripping assembly disposed between the balance piston seal and the stationary support. The balance piston seal may be configured to be disposed about the balance piston such that an inner radial surface of the balance piston seal and an outer radial surface of the balance piston define a radial clearance therebetween. The stationary support may be configured to be coupled or integral with a casing of the compressor. The gripping assembly may be configured to secure the balance piston seal with the stationary support and to maintain concentricity between the balance piston seal and the balance piston during thermal radial expansion of the balance piston seal relative to the balance piston.