Screw Compressor Oil Re-Entrainment Prevention

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Solution Overview

Problem

In oil-flooded screw compressors, oil separation is inefficient due to oil being re-entrained with the compressed medium at the demistor, leading to unwanted mixing with refrigerant gas.

Innovation Solution

A screw compressor design featuring a first and second volume separated by a demistor, with an oil discharge device on the housing inner wall to prevent re-entrainment of separated oil, using a channel-shaped oil discharge device that guides oil downwards to an oil sump, ensuring effective oil separation and preventing re-mixing with the compressed medium.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If oil pre-separation takes place at the boundary wall of the first volume, then oil separation efficiency is improved, but separated oil is re-entrained by the compressed medium and mixes again with the refrigerant gas

Engineering Contradiction:
Improveoil separation efficiencyVSAvoidoil re-entrainment and mixing with refrigerant gas
Core Design Contradiction:
Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The invention extracts the separated oil from the flow path by providing a dedicated oil drain or oil trap on the separating device. This removes the separated oil droplets that have accumulated on the inner wall before they can be re-entrained by the compressed medium passing through the demistor, thus eliminating the harmful re-mixing effect while preserving the separation efficiency

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The oil drain or oil trap acts as an intermediary element between the separation zone (first volume) and the outlet (second volume). It captures and removes separated oil droplets from the boundary wall, preventing them from being picked up by the gas flow and re-introduced into the refrigerant stream, thereby resolving the contradiction between separation and re-entrainment

Inventive Principle:
Principle #24Intermediary (Mediator)

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 design enhances oil separation efficiency by preventing oil re-mixing with the compressed medium, ensuring cleaner refrigerant gas output and improved compressor performance.

Implementation Method 1

A portion of the oil separates at a boundary wall of the first volume and flows downwards along this wall due to inertia

Methodology Applied
Scientific EffectInertial impaction: Inertia

Implementation Method 2

oil pre-separation takes place before the mixture passes through the demistor

Methodology Applied
Scientific EffectCoalescence: Cohesion

Implementation Method 3

A portion of the oil separates at a boundary wall of the first volume and flows downwards along this wall due to inertia

Methodology Applied
Scientific EffectGravity: Gravitation

Data Source

PatentEP3080458B1Compressor
Publication Date: 2020.10.07 GEA REFRIGERATION GERMANY GMBH
  • EP3080458B1 patent drawingFigure 1
  • EP3080458B1 patent drawingFigure 2

AI summary

The invention relates to a screw compressor (10) comprising a compressor device (18), in particular at least one screw rotor (20, 22), which guides a compressed medium to an oil separating device (30). Said compressor (10) has a first volume (32) and a second volume (34), in addition to a separating device (36) separating the first and the second volumes (32, 34) from each other. The first volume (32) is defined by a housing inner wall (52) and the separating device (36) which separates the first volume (32) from the second volume (34). Said separating device (36) comprises a demistor (40) and an oil discharging device (54) is arranged on the separating device (36).