Asymmetric Rotor End Seal for Screw Compressor Leakage

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Solution Overview

Problem

In screw-type compressors, the shortening of rotors to make the compressor more compact reduces the opportunity for economizer flow injection, leading to inefficiencies in sealing and increased power requirements due to premature closure of suction ports.

Innovation Solution

A compressor design featuring a rotor end seal with an asymmetric engagement face and a full-annulus base portion to resist leakage from economizer ports to suction plenums while allowing axial flow components, enabling earlier closure of radial suction ports without compromising the sealing of axial suction ports.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the rotor length is shortened to make the compressor more compact, then the compressor size is reduced, but the opportunity for economizer flow injection is reduced

Engineering Contradiction:

Improvecompressor sizeVSAvoidcompression process length

Core Design Contradiction:

Volume of moving objectVSDuration of action of moving object

Solution Approach 1:

The patent applies asymmetry by providing an end seal with an asymmetric engagement face that has different sealing characteristics at different angular positions around the rotor axis. The engagement face includes a first portion with a first sealing characteristic and a second portion with a second sealing characteristic, allowing differential sealing behavior that enables earlier radial port closure while maintaining axial port sealing and economizer flow injection opportunity

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent applies local quality by creating different sealing properties at different locations of the end seal. The engagement face has varying sealing characteristics across its surface, with certain angular regions providing stronger sealing than others. This localized variation in sealing quality allows the system to close radial suction ports earlier while still maintaining adequate sealing for axial ports and economizer flow paths

Inventive Principle:

Principle #3Local quality

2Volume of moving object

If the radial suction port is closed off sooner to allow shorter rotors, then the compressor becomes more compact, but the axial suction port cannot be closed properly

Engineering Contradiction:

Improverotor lengthVSAvoidsuction port sealing

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The asymmetric engagement face is designed with different portions that seal against different rotor surfaces at different times during rotation. This asymmetry allows the seal to effectively close the radial suction port earlier in the rotation cycle while simultaneously maintaining proper sealing of the axial suction port, resolving the timing conflict between the two port closures

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The engagement face is segmented into different portions with different sealing characteristics. The first portion seals against one rotor surface while the second portion seals against another rotor surface, allowing independent control of sealing timing for different suction ports. This segmentation enables the radial port to close sooner while the axial port closes at the appropriate later time

Inventive Principle:

Principle #1Segmentation

3Length of moving object

If the rotor length is shortened, then the compression path is shorter, but the time required for economizer flow injection is reduced

Engineering Contradiction:

Improverotor lengthVSAvoidpower consumption

Core Design Contradiction:

Length of moving objectVSUse of energy by moving object

Solution Approach 1:

The asymmetric sealing characteristics create a timing window that extends the effective period for economizer flow injection. By having different portions of the engagement face seal at different times, the system maintains adequate sealing while allowing economizer flow to be injected over a longer duration, reducing the power required for compression

Inventive Principle:

Principle #4Asymmetry

Data Source

PatentUS7802974B2Screw compressor having asymmetric seal around rotor axis

Publication Date: 2010.09.28 CARRIER CORP

AI summary

A compressor includes a male rotor (26) having a screw-type boy portion (30) extending from a first end (31) to a second end (32) and held within a housing assembly for rotation about a first rotor axis (500). A female rotor (27, 28) has a screw-type female body portion (33, 34) meshed with the male body portion and extending from a first end (35, 36) to a second end (37, 38) and held within the housing assembly for rotation about a second rotor axis (501, 502). An end seal (120) has a first surface (126) engaging the female body portion first end and being asymmetric around the second axis.