Hermetic Scroll Compressor Intermediate Pressure Oil Return
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Solution Overview
Problem
Hermetic type scroll compressors using CO2 refrigerant face challenges with increased operating pressure, leading to higher material requirements for the casing, increased weight, and cost, as well as inadequate lubrication and reliability due to high pressure differentials and foreign object obstruction in oil flow passages.
Innovation Solution
A hermetic type scroll compressor design with an oil return mechanism that intermittently returns lubricating oil from an oil separator to the hermetic casing and an oil supply mechanism that intermittently supplies oil to sliding parts, maintaining intermediate pressure between suction and discharge pressures, using an oil return passage and oil pocket, and oiling grooves to ensure reliable lubrication and reduced material thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a high-pressure casing is used to secure adequate strength against CO2 operating pressure (about 10 MPa), then the strength and reliability of the compressor is improved, but the casing requires thick material which increases the weight and cost
Solution Approach 1:
The hermetic casing is divided into a high-pressure casing (discharge side) and a low-pressure casing (suction side), separated by an intermediate pressure casing. This segmentation allows each casing to be designed for its specific pressure level, reducing the need for thick material throughout the entire casing structure.
Solution Approach 2:
Different parts of the casing are designed with different pressure ratings matching their local requirements. The discharge side uses high-pressure casing for strength, while the suction side uses low-pressure casing for weight reduction, with the intermediate pressure casing serving as a transition zone.
2Weight of moving object
If a low-pressure casing is used with CO2 refrigerant, then the weight and cost are reduced, but the lubricating oil in the suction gas separates into droplets and flows into the working chamber causing inadequate lubrication and reliability issues
Solution Approach 1:
An intermediate pressure casing is introduced as a mediator between the low-pressure suction side and high-pressure discharge side. This intermediate pressure environment prevents oil droplet separation while allowing the use of lighter materials, and oil return passages actively manage oil flow to ensure proper lubrication.
Solution Approach 2:
Oil return passages are implemented to actively manage lubricating oil flow using pressure differentials and fluid dynamics principles, ensuring oil is returned to the appropriate chambers for proper lubrication without requiring the entire casing to be high-pressure rated.
3Ease of operation
If capillary tubes with reduced inside diameters are used to control oil flow rates in CO2 refrigerant system, then the oil flow control is improved, but foreign objects such as wear particles easily obstruct the passages reducing reliability
Solution Approach 1:
Instead of using fixed small-diameter capillary tubes, the system uses dynamically adjustable oil flow control through passages that can adapt to varying operating conditions, and incorporates oil separators and return mechanisms that actively manage oil flow, preventing foreign object accumulation and obstruction.
Solution Approach 2:
Oil separators are implemented to remove lubricating oil from the CO2 refrigerant discharge, and oil return passages actively return the oil to the appropriate chambers. This recovery system prevents oil and foreign particles from accumulating in narrow passages, maintaining reliable operation.
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 enhances the performance and reliability of the compressor while reducing costs by maintaining intermediate pressure, preventing foreign object obstruction, and ensuring effective lubrication of sliding parts, even with CO2 as the refrigerant, thus addressing the issues of weight and material thickness.
Implementation Method 1
the orbiting scroll, without rotating on its own axis relative to the fixed scroll, revolves orbitally at an approximately constant radius, thereby reducing the volume of a working chamber formed between the two scroll wraps and causing working fluid to be compressed
Implementation Method 2
The interior of the hermetic casing is kept at an intermediate pressure between a suction pressure and a discharge pressure
Implementation Method 3
an oil return mechanism which intermittently returns lubricating oil from the oil separator into the hermetic casing
Implementation Method 4
an oil supply mechanism which intermittently supplies lubricating oil from around the circumference of the orbiting scroll end plate to the sliding parts of the mutually sliding orbiting scroll end plate and fixed scroll end plate
Data Source
AI summary
A hermetic type scroll compressor according to the invention includes a scroll compressor element in which an end plate of a orbiting scroll and an end plate of a fixed scroll are assembled such that they slide against each other, an electric motor element which drives the scroll compressor element, a hermetic casing housing the scroll compressor element and the electric motor element and holding lubricating oil collected at a bottom thereof, and an oil separator disposed on a discharge side of the scroll compressor element. An interior of the hermetic casing is kept at an intermediate pressure between a suction pressure and a discharge pressure. An oil return mechanism is provided, which intermittently returns lubricating oil from the oil separator to sliding parts of the orbiting scroll end plate and the fixed scroll end plate. The hermetic type scroll compressor 31 can be improved in performance and reliability while promoting cost reduction.