Screw Compressor Oil Supply via Segmented Separation

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Solution Overview

Problem

In oil cooling type screw compressors, direct return of oil with hot-temperature air to the suction port or tooth groove leads to degraded volume efficiency and increased power consumption due to oil shortage and backflow issues.

Innovation Solution

A compressor design that includes a primary and secondary oil separation system, where the secondary separation oil is mixed with compressed gas and supplied to the compression tooth groove space, promoting oil dispersion and atomization, thereby preventing oil shortage and backflow, and enhancing cooling efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If oil is directly returned to the suction port or tooth groove, then oil separation is achieved, but volume efficiency is degraded and power consumption increases

Engineering Contradiction:
Improveoil separationVSAvoidvolume efficiency
Core Design Contradiction:
ReliabilityVSProductivity

Solution Approach 1:

The patent segments the oil return process into two distinct paths: primary separation oil is supplied to the tooth groove space, while secondary separation oil is returned to the suction port. This segmentation prevents hot oil with large air content from directly entering the compression zone, thereby maintaining volume efficiency while achieving effective oil separation.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent applies different quality requirements to different oil return locations. Oil supplied to the tooth groove space requires higher separation quality to prevent backflow, while oil returned to the suction port can tolerate more air content. This local differentiation of oil quality resolves the contradiction between separation effectiveness and volume efficiency.

Inventive Principle:
Principle #3Local quality

2Reliability

If oil is directly returned to the suction port or tooth groove, then oil separation is achieved, but power consumption increases

Engineering Contradiction:
Improveoil separationVSAvoidpower consumption
Core Design Contradiction:
ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent segments the oil return process into two distinct paths: primary separation oil is supplied to the tooth groove space, while secondary separation oil is returned to the suction port. This segmentation prevents hot oil with large air content from directly entering the compression zone, thereby maintaining volume efficiency while achieving effective oil separation.

Inventive Principle:
Principle #1Segmentation

3Reliability

If secondary separation oil is supplied alone to the compression tooth groove space, then oil separation is improved, but oil dispersion is insufficient and deflection occurs

Engineering Contradiction:
Improveoil separationVSAvoidoil dispersion
Core Design Contradiction:
ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent merges primary separation oil and secondary separation oil in the tooth groove space. The primary separation oil acts as a carrier fluid that promotes dispersion of the secondary separation oil, preventing deflection and ensuring stable oil distribution in the compression zone.

Inventive Principle:
Principle #5Merging (Combining)

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 design reduces the power needed to drive the compressor by improving sealing performance, increasing air discharge, and enhancing the cooling process efficiency, leading to a more isothermal compression state.

Implementation Method 1

a primary separation unit which primarily separates an oil from the gas compressed by the compressor body

Methodology Applied
Scientific EffectCentrifugal force: Centrifugal Force

Implementation Method 2

a secondary separation unit which secondarily separates an oil from the gas from which the oil is primarily separated by the primary separation unit

Methodology Applied
Scientific EffectFiltration: Filter (physical)

Implementation Method 3

the fluid mixture of the primarily separated oil and the pressurized gas is supplied to the compression tooth groove space of the female rotor. Accordingly, when the fluid mixture is released to the compression tooth groove space of the female rotor, the dispersion of the oil is promoted

Methodology Applied
Scientific EffectDispersion: Dispersion (of waves)

Implementation Method 4

the atomization of the oil is promoted, and hence the surface area of the oil with respect to the amount of the oil supplied to the female rotor increases

Methodology Applied
Scientific EffectAtomization:

Implementation Method 5

heat is easily exchanged between the oil supplied to the compressor body and the gas in the course of compression. Accordingly, since the efficiency of the cooling process using the oil is improved

Methodology Applied
Scientific EffectHeat exchange: Heat Exchanger

Data Source

PatentEP2863060B2Screw Compressor and oil supply method thereof
Publication Date: 2019.03.20 KOBE STEEL LTD
  • EP2863060B2 patent drawingFigure 1A~1C
  • EP2863060B2 patent drawingFigure 2~3
  • EP2863060B2 patent drawingFigure 4~5

AI summary

Screw compressor and oil supply method thereof, the compressor including: a compressor body (10) that includes a suction port (13) which suctions a gas, a female rotor (22) and a male rotor (24) which compress the gas in cooperation with a rotor chamber (11), and an discharge port (14) which discharges the gas; an oil collector (30) that includes a primary separation unit (34) and a secondary separation unit (32); a primary separation oil supply line (41) that is connected to a compression tooth groove space (27) of the female rotor (22) defined by an inner wall of the rotor chamber (11) and a pair of adjacent teeth of the female rotor (22) in a cross-section perpendicular to a rotor shaft and the oil collector (30) and supplies a primarily separated oil to the compression tooth groove space (27) of the female rotor (22); an oil drain line (54), and a secondary separation oil supply line (52) that supplies a secondarily separated oil to the compression tooth groove space (27) of the female rotor (22) and is connected to the primary separation oil supply line (41).