Scroll Compressor Back-Pressure Passage for Stable Capacity Modulation
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Solution Overview
Problem
Existing scroll compressors with capacity modulation suffer from unstable operation due to insufficient pressure in the back pressure chamber.
Innovation Solution
A scroll compressor design with an orbiting scroll, fixed scroll, and at least two capacity modulation structures, featuring a back pressure passage and recesses with bypass ports, where the back pressure passage is positioned closer to the center than the bypass ports, ensuring stable operation by maintaining back pressure greater than suction but less than discharge pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If capacity modulation structures are added to the scroll compressor, then energy efficiency ratio (EER) performance is improved, but scroll operation stability deteriorates due to insufficient back pressure chamber pressure
Solution Approach 1:
A back pressure passage is introduced as an intermediary element to connect the back pressure chamber with the discharge passage. This passage mediates the pressure distribution, ensuring sufficient back pressure is maintained in the chamber even when capacity modulation structures are active, thereby preventing scroll operation instability while preserving EER improvements
Solution Approach 2:
The back pressure passage enables dynamic adjustment of back pressure chamber pressure as a controlling parameter. By regulating the pressure level in the back pressure chamber through the passage, the system can maintain stable scroll operation across different capacity modulation states while achieving improved EER performance
2Stability of the object's composition
If back pressure is increased to stabilize scroll operation, then scroll operation stability is improved, but discharge pressure may exceed required levels affecting system performance
Solution Approach 1:
The back pressure passage is positioned at a specific radial location closer to the center than bypass ports, creating a localized pressure regulation zone. This local quality approach ensures back pressure is increased only where needed for scroll stability, while the overall discharge pressure remains controlled and appropriate for system performance
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
Stabilizes scroll operation by maintaining appropriate back pressure, enhancing energy efficiency ratio (EER) performance and preventing unstable operation during capacity modulation.
Implementation Method 1
a radial distance between the back pressure passage and a center position of the fixed scroll wrap is smaller than a radial distance between each of the bypass ports communicating with the first fluid pocket, and the center position
Data Source
AI summary
An end plate of a fixed scroll of a scroll compressor has a back pressure passage, at least two recesses and a plurality of bypass ports. The back pressure passage communicates a first fluid pocket of the two fluid pockets with a back pressure chamber, each of the bypass ports communicates one of the fluid pockets with one of the recesses, and a piston assembly of one of the capacity modulation structures is movably installed in each of the recesses. A radial distance between the back pressure passage and a center position of the fixed scroll wrap is smaller than a radial distance between each of the bypass ports communicating with the first fluid pocket, and the center position. In a capacity modulation mode, the back pressure passage provides appropriate back pressure for the back pressure chamber, to ensure stable operation of the scroll members.