Multistage Compressor Oil Routing Around a Pressure Reducing Element

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Solution Overview

Problem

In multistage compression systems, uneven distribution of oil across compressors can occur due to the placement of oil drain passages relative to pressure reducing elements like intercoolers or refrigerant merging points, affecting the amount of refrigerant and oil passing through, and thus requiring precise positioning of oil drain passages to maintain optimal oil levels.

Innovation Solution

The multistage compression system incorporates an oil discharge pipe that connects the low-stage compressor to a downstream portion of the refrigerant pipes, specifically after a pressure reducing element, to control the amount of oil discharged and maintain appropriate oil levels in the low-stage compressor, with additional configurations involving intercoolers and merging parts to enhance oil management.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the oil drain passage is connected to the refrigerant pipe upstream of the pressure reducing element, then the oil level in the low-stage compressor can be maintained, but the amount of oil discharged becomes insufficient when the pressure reducing element is present

Engineering Contradiction:

Improveamount of oil dischargedVSAvoidoil level control

Core Design Contradiction:

Quantity of substanceVSEase of operation

Solution Approach 1:

The invention changes the connection position parameter of the oil drain passage from upstream to downstream of the pressure reducing element. This parameter change exploits the pressure difference created by the pressure reducing element to increase the discharge amount of oil, while still maintaining proper oil level control in the low-stage compressor through the return passage configuration.

Inventive Principle:

Principle #35Parameter changes

2Temperature

If the pressure reducing element is provided in the refrigerant pipe, then refrigerant cooling or intermediate injection is achieved, but the amount of refrigerant and oil passing through the oil drain passage varies affecting oil level

Engineering Contradiction:

Improverefrigerant temperatureVSAvoidamount of oil in low-stage compressor

Core Design Contradiction:

TemperatureVSQuantity of substance

Solution Approach 1:

The invention applies local quality by providing different connection positions for the oil drain passage and oil return passage relative to the pressure reducing element. The oil drain passage connects downstream to utilize pressure difference for discharge, while the oil return passage connects upstream to ensure proper oil level maintenance, creating localized functional differences in the same refrigerant circuit.

Inventive Principle:

Principle #3Local quality

3Quantity of substance

If the oil discharge pipe connects to the refrigerant pipe downstream of the pressure reducing element, then the amount of oil discharged increases, but the connection position must be precisely selected to maintain optimal oil levels

Engineering Contradiction:

Improveamount of oil dischargedVSAvoidconnection position selection

Core Design Contradiction:

Quantity of substanceVSManufacturing precision

Solution Approach 1:

The invention introduces an intermediary oil return passage that connects the refrigerant pipe upstream of the pressure reducing element to the low-stage compressor. This intermediary passage compensates for the increased oil discharge caused by the downstream connection, maintaining optimal oil levels without requiring precise connection position selection.

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 ensures appropriate control of oil levels in the low-stage compressor, preventing excessive oil accumulation and ensuring efficient operation by optimizing the connection positions of the oil discharge and return pipes relative to the compressors and pressure reducing elements.

Implementation Method 1

a pressure of the refrigerant pipe reduces

Methodology Applied

Scientific EffectPressure reduction: Pressure Drop

Implementation Method 2

The oil discharge pipe connects the low-stage compressor and a portion of the refrigerant pipes, which is a downstream side of the pressure reducing element

Methodology Applied

Scientific EffectPressure gradient flow: Pressure Gradient

Data Source

PatentUS11428226B2Multistage compression system

Publication Date: 2022.08.30 DAIKIN INDUSTRIES LTD

AI summary

A multistage compression system uses refrigerant and oil. The multistage compression system includes a low-stage compressor that compresses the refrigerant, a high-stage compressor that further compresses the refrigerant compressed by the low-stage compressor, refrigerant pipes that-introduce the refrigerant compressed and discharged by the low-stage compressor into a suction part of the high-stage compressor, a pressure reducing element disposed between the refrigerant pipes, an accumulator disposed between the refrigerant pipes at a downstream side of the pressure reducing element and at an upstream side of the high-stage compressor, and an oil discharge pipe. The oil discharge pipe discharges the oil in the low-stage compressor. The oil discharge pipe connects the low-stage compressor and a portion of the refrigerant pipes. The portion of the refrigerant pipes is on a downstream side of the pressure reducing element and an upstream side of the accumulator.