Two-Stage Screw Compressor Sealing Layout to Prevent Refrigerant Leakage

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Solution Overview

Problem

Existing two-stage screw compressors face challenges in completely sealing rotating shafts, leading to refrigerant leakage, especially when compressing toxic refrigerants like ammonia.

Innovation Solution

A sealed configuration where the connection space between the first-stage and second-stage compressors serves as both a flow passage and a transmission mechanism, eliminating the need for external sealing of rotating shafts and ensuring all shafts are enclosed within the casing, preventing fluid leakage and pressure differences that could cause bearing issues.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a mechanical seal is used to seal the drive shaft passing through the box body, then the structure is simple and easy to manufacture, but the seal is not complete and refrigerant leaks occur

Engineering Contradiction:

Improvesealing performanceVSAvoidsealing structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the motor casing with the box body to create an integrated sealed enclosure. The motor casing and box body form a unified structure that completely encloses the drive shaft, eliminating the need for separate mechanical seals at shaft pass-through points. This integration achieves complete sealing while maintaining structural simplicity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The drive shaft is nested within the sealed enclosure formed by the motor casing and box body. The transmission mechanism components are nested within the connection space, creating a hierarchical enclosed structure that prevents refrigerant leakage while organizing mechanical components efficiently.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Reliability

If rotating shafts are sealed from the outside using mechanical seals, then the structure is straightforward, but complete sealing is difficult to achieve and refrigerant leakage occurs

Engineering Contradiction:

Improvesealing completenessVSAvoidmanufacturing difficulty

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

Instead of sealing the shaft from the outside using mechanical seals, the patent inverts the approach by enclosing the entire shaft and transmission mechanism within a sealed motor casing integrated with the box body. This internal enclosure approach achieves complete sealing without the complexity of external mechanical seals.

Inventive Principle:

Principle #13The other way round (Inversion)

3Reliability

If the connection space is sealed and integrated with the motor casing, then refrigerant leakage is prevented, but the structure becomes more complex

Engineering Contradiction:

Improveleakage preventionVSAvoidcasing structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The motor casing and box body are merged into an integrated sealed structure that encloses the connection space, transmission mechanism, and motor components. This merging achieves complete leakage prevention while the integration actually simplifies the overall structure by eliminating separate sealing components and reducing the number of parts.

Inventive Principle:

Principle #5Merging (Combining)

4Reliability

If the motor internal space communicates with the connection space, then pressure differences are eliminated and bearing issues are prevented, but the structure requires careful design

Engineering Contradiction:

Improvebearing protectionVSAvoidpressure balance structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The motor internal space and connection space are connected to create a pressure-equalized environment. This equipotential design eliminates pressure differences that would otherwise cause refrigerant to blow through bearings, protecting the bearing system while maintaining a simple pressure-balanced structure.

Inventive Principle:

Principle #12Equipotentiality

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 prevents refrigerant leakage, maintains a sealed environment, and allows for efficient cooling of the motor using the compressed fluid, reducing the risk of overheating and vibration, while using a separate jacket for additional cooling without direct fluid contact.

Implementation Method 1

cause the fluid to be compressed to cool an interior of the motor

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Implementation Method 2

cool the motor using a refrigerant other than the fluid to be compressed

Methodology Applied

Scientific EffectHeat transfer: Convection

Data Source

PatentUS8205469B2Two-stage screw compressor and refrigerating device

Publication Date: 2012.06.26 KOBELCO COMPRESSORS CORP

AI summary

There is provided a two-stage screw compressor including a first-stage compressor that compresses a fluid, a second-stage compressor that further compresses the fluid compressed by the first-stage compressor, a motor that drives the first-stage compressor and the second-stage compressor, and a box body that serves as a flow passage connecting an outlet of the first-stage compressor and an inlet of the second-stage compressor, and also forms a connection space storing a transmission mechanism for transmitting a rotation force from the motor to the first-stage compressor and to the second-stage compressor, wherein the connection space is sealed by the casing of the motor, and the connection space and an internal space of the casing of the motor communicate with each other.