Centrifugal Compressor Cooling Oil Passage Design

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Solution Overview

Problem

In turbochargers, the high temperature of lubricating oil sprayed onto the seal plate of the centrifugal compressor reduces its cooling effectiveness, leading to inadequate cooling of compressed air, especially with increasing temperatures due to EGR and lean burn Miller cycles.

Innovation Solution

A centrifugal compressor design with a separate oil flow passage for cooling oil that bypasses the bearing member, allowing cooling oil to directly exchange heat with compressed air without passing through the bearing, thereby reducing its temperature and improving cooling performance, while also circulating lubricating oil to reduce mechanical losses and maintain efficient lubrication.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If lubricating oil is sprayed to the seal plate after lubricating the bearing, then the bearing is lubricated, but the temperature of the lubricating oil rises and cooling performance deteriorates

Engineering Contradiction:
Improvebearing lubricationVSAvoidcooling oil temperature
Core Design Contradiction:
ReliabilityVSTemperature

Solution Approach 1:

The patent divides the oil flow passage into separate lubricating oil passage and cooling oil passage, segmenting the oil flow paths to enable independent temperature control for lubrication and cooling functions

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent extracts the cooling oil passage from the bearing member, allowing cooling oil to flow independently without passing through the bearing, thus preventing temperature rise from bearing friction

Inventive Principle:
Principle #2Taking out (Extraction)

2Reliability

If cooling oil flows through the bearing member, then the bearing is lubricated, but the cooling oil temperature rises and cooling effectiveness decreases

Engineering Contradiction:
Improvebearing lubricationVSAvoidcooling performance
Core Design Contradiction:
ReliabilityVSProductivity

Solution Approach 1:

The patent segments the oil circulation system into distinct lubrication and cooling circuits, allowing optimized flow paths for each function

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent introduces a separate cooling oil passage as an intermediary path that enables cooling oil to reach the seal plate without passing through the bearing, thus maintaining low temperature

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

This configuration enhances the cooling performance of the centrifugal compressor by maintaining lower cooling oil temperatures for effective heat exchange and reduces mechanical losses through optimized lubrication, thus preventing increased air temperatures and improving engine efficiency.

Implementation Method 1

a cooling oil passage through which the oil flows as cooling oil for heat exchange with air compressed by the impeller

Methodology Applied
Scientific EffectHeat exchange: Heat Exchanger

Implementation Method 2

a lubricating oil passage through which the oil flows as lubricating oil to be supplied to the bearing member

Methodology Applied
Scientific EffectLubrication: Lubrication

Data Source

PatentEP3786459B1Centrifugal compressor and turbocharger equipped with centrifugal compressor
Publication Date: 2023.08.16 MITSUBISHI HEAVY IND ENGINE & TURBOCHARGER LTD
  • EP3786459B1 patent drawingFigure 1
  • EP3786459B1 patent drawingFigure 2
  • EP3786459B1 patent drawingFigure 3

AI summary

A centrifugal compressor includes: a housing; an impeller rotatably disposed within the housing; a rotational shaft connected to the impeller; and a bearing member supporting the rotational shaft in the housing. An oil flow passage through which oil flows is formed in the housing. The oil flow passage includes a lubricating oil passage through which the oil flows as lubricating oil to be supplied to the bearing member, and a cooling oil passage through which the oil flows as cooling oil for heat exchange with a fluid compressed by the impeller. The cooling oil passage is configured so that the oil flows into the cooling oil passage as the cooling oil without passing through the bearing member.