Parallel Compressor Oil Equalization for Stable Sump Lubrication

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Solution Overview

Problem

Existing compression devices in refrigeration systems face challenges in maintaining balanced oil levels between compressors, especially when one compressor is stopped, leading to oil flow imbalances and potential damage due to insufficient lubrication.

Innovation Solution

The compression device incorporates an oil level equalization line with a dam wall and flow opening that regulates oil and refrigerant flow between compressors, ensuring a minimum oil level in each sump and preventing excessive oil accumulation, regardless of operating conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a restricting member is positioned in one of the suction pipes to balance oil levels, then oil level balancing is improved, but pressure equalization fails when one compressor is stopped

Engineering Contradiction:

Improveoil level balancingVSAvoidpressure equalization under different operating conditions

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

A three-way valve is introduced as an intermediary component to control the oil level equalization line. This valve acts as a mediator that can selectively connect or disconnect the equalization line based on operating conditions, allowing the system to adapt between single-compressor and dual-compressor modes while maintaining reliable oil level balancing

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If the compression device operates with one compressor stopped, then operational flexibility is improved, but oil level imbalance and foaming occur

Engineering Contradiction:

Improveoperational flexibilityVSAvoidoil level stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The system transitions from a static restricting member to a dynamic control system using a three-way valve that can change its configuration based on operating conditions. When one compressor is stopped, the valve dynamically adjusts to open the oil level equalization line, enabling the system to adapt to single-compressor operation while maintaining oil level stability and preventing foaming

Inventive Principle:

Principle #15Dynamics

3Device complexity

If a restricting member is used to limit pressure deviation, then device complexity is reduced, but oil loss through the equalization line increases

Engineering Contradiction:

Improvestructure simplicityVSAvoidoil loss

Core Design Contradiction:

Device complexityVSLoss of substance

Solution Approach 1:

The three-way valve implements a feedback-controlled mechanism that monitors operating conditions and adjusts the equalization line connectivity accordingly. By detecting when one compressor is stopped, the system activates the equalization line only when needed, preventing unnecessary oil loss while maintaining simple overall device structure

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system changes the flow parameters in the equalization line dynamically by using the three-way valve to control connectivity. This allows the system to maintain low oil loss during normal operation by keeping the equalization line closed, while enabling oil balancing when required by changing the connectivity parameter

Inventive Principle:

Principle #35Parameter changes

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 maintains a stable oil level in each compressor, preventing oil droplet discharge and ensuring adequate lubrication, thereby enhancing the reliability and longevity of the compression device.

Implementation Method 1

an oil level equalization line (44) arranged to fluidly connect the oil sumps (31) of the first and second compressors (7, 8), the oil level equalization line (44) comprising at least one oil level regulating portion (45) positioned near one of the first and second compressors (7, 8), the oil level regulating portion (45) comprising a dam wall (48) extending transversely to a longitudinal direction of the oil level regulating portion (45) and a flow opening (51)

Methodology Applied

Scientific EffectHydraulic control: Hydraulic Press

Implementation Method 2

arranged and sized such that an upper portion of the flow section of the equalization line is designed to transfer refrigerant between the first and second compressors (7, 8), and a lower portion of the flow section of the equalization line is designed to transfer oil between the first and second compressors (7, 8)

Methodology Applied

Scientific EffectPressure gradient: Pressure Gradient

Data Source

PatentUS9273678B2Compression device, and thermodynamic system comprising such a compression device

Publication Date: 2016.03.01 DANFOSS COMML COMPRESSORS SA

AI summary

The compression device according to the invention includes first and second compressors mounted in parallel and an oil level equalization line arranged to fluidly connect the oil sumps of the first and second compressors. The oil level equalization line includes at least one oil level regulating portion positioned near one of the first and second compressors and including a dam wall extending transversely to the longitudinal direction of said oil level regulating portion and a flow opening arranged such that, when the oil level in the oil sump of the compressor situated near the oil level regulating portion extends above the upper level of the dam wall, oil flows through the flow opening toward the other compressor.